Author: "Arenas G" / Database: OAIster - Searchworks@Jio Institute Digital Library Search Results

Your search keyword '"Arenas G"' showing total 61 results

Start Over Author "Arenas G" Database OAIster

61 results on '"Arenas G"'

1. Measurement of the intrinsic hadronic contamination in the NA64$-e$ high-purity $e^+/e^-$ beam at CERN

Author: Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondi, M., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., H"osgen, M., Jeckel, M., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Gertsenberger, S. V., Kasianova, E. A., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marini, A., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Salamatin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Soto, O., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Tuzi, M., Ulloa, P., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Sa'a, J., Zhevlakov, A. S., Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondi, M., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., H"osgen, M., Jeckel, M., Kachanov, V. A., Kambar, Y., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Gertsenberger, S. V., Kasianova, E. A., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marini, A., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Mongillo, M., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Salamatin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Soto, O., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Tuzi, M., Ulloa, P., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Voronchikhin, I. V., Zamora-Sa'a, J., and Zhevlakov, A. S.
Abstract: In this study, we present the measurement of the intrinsic hadronic contamination at the CERN SPS H4 beamline configured to transport electrons and positrons at 100 GeV/c momentum. The analysis was performed using data collected by the NA64-$e$ experiment in 2022. Our study is based on calorimetric measurements, exploiting the different interaction mechanisms of electrons and hadrons in the NA64-ECAL and NA64-HCAL detectors. We determined the intrinsic hadronic contamination by comparing the results obtained using the nominal electron/positron beamline configuration with those obtained in a dedicated setup, in which only hadrons impinged on the detector. The significant differences in the experimental signatures of electrons and hadrons motivated our approach, resulting in a small and well-controlled systematic uncertainty for the measurement. Our study allowed us to precisely determine the intrinsic hadronic contamination, which represents a crucial parameter for the NA64 experiment in which the hadron contaminants may result in non-trivial backgrounds. Moreover, we performed dedicated Monte Carlo simulations for the hadron production induced by the primary T2 target. We found a good agreement between measurements and simulation results, confirming the validity of the applied methodology and our evaluation of the intrinsic hadronic contamination.
Published: 2023

2. Search for a light muon-philic $Z^\prime$ with the NA64-$e$ experiment at CERN

Author: Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondì, M., Burtsev, V. E., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hösgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samalantin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu, Ulloa, P., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Voronchikhin, I., Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondì, M., Burtsev, V. E., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hösgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samalantin, K., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu, Ulloa, P., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Voronchikhin, I.
Abstract: The extension of Standard Model made by inclusion of additional $U(1)$ gauge $L_\mu-L_\tau$ symmetry can explain the difference between the measured and the predicted value of the muon magnetic moment and solve the tension in $B$ meson decays. This model predicts the existence of a new, light $Z^\prime$ vector boson, predominantly coupled to second and third generation leptons, whose interaction with electrons is due to a loop mechanism involving muons and taus. In this work, we present a rigorous evaluation of the upper limits in the $Z^\prime$ parameter space, obtained from the analysis of the data collected by the NA64-$e$ experiment at CERN SPS, that performed a search for light dark matter with $2.84\times10^{11}$ electrons impinging with 100 GeV on an active thick target. The resulting limits, despite being included in a region already investigated by neutrino experiments,touch the muon $g-2$ preferred band for values of the $Z^\prime$ mass of order of 1 MeV. The sensitivity projections for the future high-statistics NA64-$e$ runs demonstrate the power of the electrons/positron beam approach in this theoretical scenario., Comment: 11 pages, 9 figures
Published: 2022

3. Search for a light muon-philic $Z^\prime$ with the NA64-$e$ experiment at CERN

Author: Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondì, M., Burtsev, V. E., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hösgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Salamatin, K. M., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu, Ulloa, P., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Voronchikhin, I., Andreev, Yu. M., Banerjee, D., Oberhauser, B. Banto, Bernhard, J., Bisio, P., Bondì, M., Burtsev, V. E., Celentano, A., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hösgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Marsicano, L., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Salamatin, K. M., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu, Ulloa, P., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Voronchikhin, I.
Abstract: The extension of Standard Model made by inclusion of additional $U(1)$ gauge $L_\mu-L_\tau$ symmetry can explain the difference between the measured and the predicted value of the muon magnetic moment and solve the tension in $B$ meson decays. This model predicts the existence of a new, light $Z^\prime$ vector boson, predominantly coupled to second and third generation leptons, whose interaction with electrons is due to a loop mechanism involving muons and taus. In this work, we present a rigorous evaluation of the upper limits in the $Z^\prime$ parameter space, obtained from the analysis of the data collected by the NA64-$e$ experiment at CERN SPS, that performed a search for light dark matter with $2.84\times10^{11}$ electrons impinging with 100 GeV on an active thick target. The resulting limits, despite being included in a region already investigated by neutrino experiments,touch the muon $g-2$ preferred band for values of the $Z^\prime$ mass of order of 1 MeV. The sensitivity projections for the future high-statistics NA64-$e$ runs demonstrate the power of the electrons/positron beam approach in this theoretical scenario., Comment: 11 pages, 9 figures. This version was accepted for publication
Published: 2022
Full Text: View/download PDF

4. Search for pseudoscalar bosons decaying into $e^+e^-$ pairs in the NA64 experiment at the CERN SPS

Author: Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: We report the results of a search for a light pseudoscalar particle $a$ that couples to electrons and decays to $e^+e^-$ performed using the high-energy CERN SPS H4 electron beam. If such pseudoscalar with a mass $\simeq 17$ MeV exists, it could explain the ATOMKI anomaly. We used the NA64 data samples collected in the "visible mode" configuration with total statistics corresponding to $8.4\times 10^{10}$ electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter $\epsilon$ we used also the data collected in 2016-2018 in the "invisible mode" configuration of NA64 with a total statistics corresponding to $2.84\times 10^{11}$ EOT. A thorough analysis of both these data samples in the sense of background and efficiency estimations was already performed and reported in our previous papers devoted to the search for light vector particles and axion-like particles (ALP). In this work we recalculate the signal yields, which are different due to different cross section and life time of a pseudoscalar particle $a$, and perform a new statistical analysis. As a result, the region of the two dimensional parameter space $m_a - \epsilon$ in the mass range from 1 to 17.1 MeV is excluded. At the mass of the ATOMKI anomaly the values of $\epsilon$ in the range $2.1 \times 10^{-4} < \epsilon < 3.2 \times 10^{-4}$ are excluded., Comment: 6 pages, 2 figures
Published: 2021
Full Text: View/download PDF

5. Probing the explanation of the muon (g-2) anomaly and thermal light dark matter with the semi-visible dark photon channel

Author: Cazzaniga, C., Odagiu, P., Depero, E., Bueno, L. Molina, Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Girod, S., Gninenko, S. N., Hösgen, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Sieber, H., Tikhomirov, V. O., Tlisova, I. V., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Cazzaniga, C., Odagiu, P., Depero, E., Bueno, L. Molina, Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Girod, S., Gninenko, S. N., Hösgen, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Sieber, H., Tikhomirov, V. O., Tlisova, I. V., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: We report the results of a search for a new vector boson ($A'$) decaying into two dark matter particles $\chi_1 \chi_2$ of different mass. The heavier $\chi_2$ particle subsequently decays to $\chi_1$ and $A' \to e^- e^+$. For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay $A'\to \chi \overline{\chi}$ and axion-like or pseudo-scalar particles $a \to \gamma \gamma$. With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for $A'$ masses from 2$m_e$ up to 390 MeV and mixing parameter $\epsilon$ between $3\times10^{-5}$ and $2\times10^{-2}$.
Published: 2021
Full Text: View/download PDF

6. Search for pseudoscalar bosons decaying into $e^+e^-$ pairs in the NA64 experiment at the CERN SPS

Author: Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: We report the results of a search for a light pseudoscalar particle $a$ that couples to electrons and decays to $e^+e^-$ performed using the high-energy CERN SPS H4 electron beam. If such pseudoscalar with a mass $\simeq 17$ MeV exists, it could explain the ATOMKI anomaly. We used the NA64 data samples collected in the "visible mode" configuration with total statistics corresponding to $8.4\times 10^{10}$ electrons on target (EOT) in 2017 and 2018. In order to increase sensitivity to small coupling parameter $\epsilon$ we used also the data collected in 2016-2018 in the "invisible mode" configuration of NA64 with a total statistics corresponding to $2.84\times 10^{11}$ EOT. A thorough analysis of both these data samples in the sense of background and efficiency estimations was already performed and reported in our previous papers devoted to the search for light vector particles and axion-like particles (ALP). In this work we recalculate the signal yields, which are different due to different cross section and life time of a pseudoscalar particle $a$, and perform a new statistical analysis. As a result, the region of the two dimensional parameter space $m_a - \epsilon$ in the mass range from 1 to 17.1 MeV is excluded. At the mass of the ATOMKI anomaly the values of $\epsilon$ in the range $2.1 \times 10^{-4} < \epsilon < 3.2 \times 10^{-4}$ are excluded., Comment: 6 pages, 2 figures
Published: 2021
Full Text: View/download PDF

7. Probing the explanation of the muon (g-2) anomaly and thermal light dark matter with the semi-visible dark photon channel

Author: Cazzaniga, C., Odagiu, P., Depero, E., Bueno, L. Molina, Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Girod, S., Gninenko, S. N., Hösgen, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Sieber, H., Tikhomirov, V. O., Tlisova, I. V., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Cazzaniga, C., Odagiu, P., Depero, E., Bueno, L. Molina, Andreev, Yu. M., Banerjee, D., Bernhard, J., Burtsev, V. E., Charitonidis, N., Chumakov, A. G., Cooke, D., Crivelli, P., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Girod, S., Gninenko, S. N., Hösgen, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Sieber, H., Tikhomirov, V. O., Tlisova, I. V., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: We report the results of a search for a new vector boson ($A'$) decaying into two dark matter particles $\chi_1 \chi_2$ of different mass. The heavier $\chi_2$ particle subsequently decays to $\chi_1$ and $A' \to e^- e^+$. For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay $A'\to \chi \overline{\chi}$ and axion-like or pseudo-scalar particles $a \to \gamma \gamma$. With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for $A'$ masses from 2$m_e$ up to 390 MeV and mixing parameter $\epsilon$ between $3\times10^{-5}$ and $2\times10^{-2}$.
Published: 2021
Full Text: View/download PDF

8. Validez de las encuestas de satisfacción de los estudiantes para evaluar la calidad docente: el caso de la UPCT (Cartagena)

Author: García Martín, A., Montero Cases, T., García León, J., Vázquez Arenas, G., García Martín, A., Montero Cases, T., García León, J., and Vázquez Arenas, G.
Abstract: [ES] El programa DOCENTIA de ANECA se desarrolló como base para los modelos mediante los cuales las universidades españolas evalúan la docencia del profesorado, una necesidad ligada a los requerimientos de transparencia y de mejora continua que están en la esencia del EEES. Entre los indicadores habituales en estos modelos destacan las encuestas de satisfacción de los estudiantes, cuya validez es objeto de debate desde el origen de su utilización. Una de las opiniones críticas más extendidas sostiene que las encuestas no son una buena referencia, porque contienen sesgos inasumibles. Con el objetivo de comprobar si existen realmente esos sesgos, se ha realizado un estudio estadístico a partir de los datos de indicadores de calidad en la Universidad Politécnica de Cartagena. Se ha empleado la regresión lineal múltiple, mediante el procedimiento conocido como regresión hacia atrás, para identificar las variables que pudieran influir en las valoraciones que hacen los estudiantes y cuantificar su efecto. El principal resultado del estudio es que las variables analizadas, que suelen citarse como causas de sesgo, muestran una influencia poco o nada significativa sobre los resultados de las encuestas. Por otra parte, es importante subrayar que hay aspectos de la actividad docente que solamente pueden evaluarse a partir de la observación sistemática que hacen los estudiantes. Por todo ello consideramos que las encuestas de satisfacción son un indicador indispensable, y es fundamental que el peso que se les asigna en el modelo de evaluación docente refleje su importancia., [EN] ANECA´s DOCENTIA program was developed to support the evaluation of teaching by the Spanish universities. Nowadays, teaching quality evaluation is a need linked to the transparency and continuous improvement requirements inherent to the European Higher Education Area. The indicators on the quality models frequently include student evaluation of teaching (SET), whose validity is the subject of a broad debate from the beginning of its use. One of the most widespread critical opinions argues that student surveys are not a good reference, as they contain non-assumable biases. With the aim of verify whether these biases actually exist, a statistical study has been carried out based on quality indicators data from the Technical University of Cartagena. Multiple linear regression has been used, through backward stepwise regression, to identify variables that may influence students’ opinions and to quantify their effects. The main result is that the variables analyzed, many of which are often cited as causes of bias, show little or no significant influence on student satisfaction with teaching. It is also important to remark that there are aspects of the teaching activity that can only be evaluated from the systematic observation made by students. Therefore, we believe that student surveys are an essential indicator, and their weight within teaching evaluation models should reflect their relevance.
Published: 2020

9. Validez de las encuestas de satisfacción de los estudiantes para evaluar la calidad docente: el caso de la UPCT (Cartagena)

Author: García Martín, A., Montero Cases, T., García León, J., Vázquez Arenas, G., García Martín, A., Montero Cases, T., García León, J., and Vázquez Arenas, G.
Abstract: [ES] El programa DOCENTIA de ANECA se desarrolló como base para los modelos mediante los cuales las universidades españolas evalúan la docencia del profesorado, una necesidad ligada a los requerimientos de transparencia y de mejora continua que están en la esencia del EEES. Entre los indicadores habituales en estos modelos destacan las encuestas de satisfacción de los estudiantes, cuya validez es objeto de debate desde el origen de su utilización. Una de las opiniones críticas más extendidas sostiene que las encuestas no son una buena referencia, porque contienen sesgos inasumibles. Con el objetivo de comprobar si existen realmente esos sesgos, se ha realizado un estudio estadístico a partir de los datos de indicadores de calidad en la Universidad Politécnica de Cartagena. Se ha empleado la regresión lineal múltiple, mediante el procedimiento conocido como regresión hacia atrás, para identificar las variables que pudieran influir en las valoraciones que hacen los estudiantes y cuantificar su efecto. El principal resultado del estudio es que las variables analizadas, que suelen citarse como causas de sesgo, muestran una influencia poco o nada significativa sobre los resultados de las encuestas. Por otra parte, es importante subrayar que hay aspectos de la actividad docente que solamente pueden evaluarse a partir de la observación sistemática que hacen los estudiantes. Por todo ello consideramos que las encuestas de satisfacción son un indicador indispensable, y es fundamental que el peso que se les asigna en el modelo de evaluación docente refleje su importancia., [EN] ANECA´s DOCENTIA program was developed to support the evaluation of teaching by the Spanish universities. Nowadays, teaching quality evaluation is a need linked to the transparency and continuous improvement requirements inherent to the European Higher Education Area. The indicators on the quality models frequently include student evaluation of teaching (SET), whose validity is the subject of a broad debate from the beginning of its use. One of the most widespread critical opinions argues that student surveys are not a good reference, as they contain non-assumable biases. With the aim of verify whether these biases actually exist, a statistical study has been carried out based on quality indicators data from the Technical University of Cartagena. Multiple linear regression has been used, through backward stepwise regression, to identify variables that may influence students’ opinions and to quantify their effects. The main result is that the variables analyzed, many of which are often cited as causes of bias, show little or no significant influence on student satisfaction with teaching. It is also important to remark that there are aspects of the teaching activity that can only be evaluated from the systematic observation made by students. Therefore, we believe that student surveys are an essential indicator, and their weight within teaching evaluation models should reflect their relevance.
Published: 2020

10. Validez de las encuestas de satisfacción de los estudiantes para evaluar la calidad docente: el caso de la UPCT (Cartagena)

Author: García Martín, A., Montero Cases, T., García León, J., Vázquez Arenas, G., García Martín, A., Montero Cases, T., García León, J., and Vázquez Arenas, G.
Abstract: [ES] El programa DOCENTIA de ANECA se desarrolló como base para los modelos mediante los cuales las universidades españolas evalúan la docencia del profesorado, una necesidad ligada a los requerimientos de transparencia y de mejora continua que están en la esencia del EEES. Entre los indicadores habituales en estos modelos destacan las encuestas de satisfacción de los estudiantes, cuya validez es objeto de debate desde el origen de su utilización. Una de las opiniones críticas más extendidas sostiene que las encuestas no son una buena referencia, porque contienen sesgos inasumibles. Con el objetivo de comprobar si existen realmente esos sesgos, se ha realizado un estudio estadístico a partir de los datos de indicadores de calidad en la Universidad Politécnica de Cartagena. Se ha empleado la regresión lineal múltiple, mediante el procedimiento conocido como regresión hacia atrás, para identificar las variables que pudieran influir en las valoraciones que hacen los estudiantes y cuantificar su efecto. El principal resultado del estudio es que las variables analizadas, que suelen citarse como causas de sesgo, muestran una influencia poco o nada significativa sobre los resultados de las encuestas. Por otra parte, es importante subrayar que hay aspectos de la actividad docente que solamente pueden evaluarse a partir de la observación sistemática que hacen los estudiantes. Por todo ello consideramos que las encuestas de satisfacción son un indicador indispensable, y es fundamental que el peso que se les asigna en el modelo de evaluación docente refleje su importancia., [EN] ANECA´s DOCENTIA program was developed to support the evaluation of teaching by the Spanish universities. Nowadays, teaching quality evaluation is a need linked to the transparency and continuous improvement requirements inherent to the European Higher Education Area. The indicators on the quality models frequently include student evaluation of teaching (SET), whose validity is the subject of a broad debate from the beginning of its use. One of the most widespread critical opinions argues that student surveys are not a good reference, as they contain non-assumable biases. With the aim of verify whether these biases actually exist, a statistical study has been carried out based on quality indicators data from the Technical University of Cartagena. Multiple linear regression has been used, through backward stepwise regression, to identify variables that may influence students’ opinions and to quantify their effects. The main result is that the variables analyzed, many of which are often cited as causes of bias, show little or no significant influence on student satisfaction with teaching. It is also important to remark that there are aspects of the teaching activity that can only be evaluated from the systematic observation made by students. Therefore, we believe that student surveys are an essential indicator, and their weight within teaching evaluation models should reflect their relevance.
Published: 2020

11. Validez de las encuestas de satisfacción de los estudiantes para evaluar la calidad docente: el caso de la UPCT (Cartagena)

Author: García Martín, A., Montero Cases, T., García León, J., Vázquez Arenas, G., García Martín, A., Montero Cases, T., García León, J., and Vázquez Arenas, G.
Abstract: [ES] El programa DOCENTIA de ANECA se desarrolló como base para los modelos mediante los cuales las universidades españolas evalúan la docencia del profesorado, una necesidad ligada a los requerimientos de transparencia y de mejora continua que están en la esencia del EEES. Entre los indicadores habituales en estos modelos destacan las encuestas de satisfacción de los estudiantes, cuya validez es objeto de debate desde el origen de su utilización. Una de las opiniones críticas más extendidas sostiene que las encuestas no son una buena referencia, porque contienen sesgos inasumibles. Con el objetivo de comprobar si existen realmente esos sesgos, se ha realizado un estudio estadístico a partir de los datos de indicadores de calidad en la Universidad Politécnica de Cartagena. Se ha empleado la regresión lineal múltiple, mediante el procedimiento conocido como regresión hacia atrás, para identificar las variables que pudieran influir en las valoraciones que hacen los estudiantes y cuantificar su efecto. El principal resultado del estudio es que las variables analizadas, que suelen citarse como causas de sesgo, muestran una influencia poco o nada significativa sobre los resultados de las encuestas. Por otra parte, es importante subrayar que hay aspectos de la actividad docente que solamente pueden evaluarse a partir de la observación sistemática que hacen los estudiantes. Por todo ello consideramos que las encuestas de satisfacción son un indicador indispensable, y es fundamental que el peso que se les asigna en el modelo de evaluación docente refleje su importancia., [EN] ANECA´s DOCENTIA program was developed to support the evaluation of teaching by the Spanish universities. Nowadays, teaching quality evaluation is a need linked to the transparency and continuous improvement requirements inherent to the European Higher Education Area. The indicators on the quality models frequently include student evaluation of teaching (SET), whose validity is the subject of a broad debate from the beginning of its use. One of the most widespread critical opinions argues that student surveys are not a good reference, as they contain non-assumable biases. With the aim of verify whether these biases actually exist, a statistical study has been carried out based on quality indicators data from the Technical University of Cartagena. Multiple linear regression has been used, through backward stepwise regression, to identify variables that may influence students’ opinions and to quantify their effects. The main result is that the variables analyzed, many of which are often cited as causes of bias, show little or no significant influence on student satisfaction with teaching. It is also important to remark that there are aspects of the teaching activity that can only be evaluated from the systematic observation made by students. Therefore, we believe that student surveys are an essential indicator, and their weight within teaching evaluation models should reflect their relevance.
Published: 2020

12. Validez de las encuestas de satisfacción de los estudiantes para evaluar la calidad docente: el caso de la UPCT (Cartagena)

Author: García Martín, A., Montero Cases, T., García León, J., Vázquez Arenas, G., García Martín, A., Montero Cases, T., García León, J., and Vázquez Arenas, G.
Abstract: [ES] El programa DOCENTIA de ANECA se desarrolló como base para los modelos mediante los cuales las universidades españolas evalúan la docencia del profesorado, una necesidad ligada a los requerimientos de transparencia y de mejora continua que están en la esencia del EEES. Entre los indicadores habituales en estos modelos destacan las encuestas de satisfacción de los estudiantes, cuya validez es objeto de debate desde el origen de su utilización. Una de las opiniones críticas más extendidas sostiene que las encuestas no son una buena referencia, porque contienen sesgos inasumibles. Con el objetivo de comprobar si existen realmente esos sesgos, se ha realizado un estudio estadístico a partir de los datos de indicadores de calidad en la Universidad Politécnica de Cartagena. Se ha empleado la regresión lineal múltiple, mediante el procedimiento conocido como regresión hacia atrás, para identificar las variables que pudieran influir en las valoraciones que hacen los estudiantes y cuantificar su efecto. El principal resultado del estudio es que las variables analizadas, que suelen citarse como causas de sesgo, muestran una influencia poco o nada significativa sobre los resultados de las encuestas. Por otra parte, es importante subrayar que hay aspectos de la actividad docente que solamente pueden evaluarse a partir de la observación sistemática que hacen los estudiantes. Por todo ello consideramos que las encuestas de satisfacción son un indicador indispensable, y es fundamental que el peso que se les asigna en el modelo de evaluación docente refleje su importancia., [EN] ANECA´s DOCENTIA program was developed to support the evaluation of teaching by the Spanish universities. Nowadays, teaching quality evaluation is a need linked to the transparency and continuous improvement requirements inherent to the European Higher Education Area. The indicators on the quality models frequently include student evaluation of teaching (SET), whose validity is the subject of a broad debate from the beginning of its use. One of the most widespread critical opinions argues that student surveys are not a good reference, as they contain non-assumable biases. With the aim of verify whether these biases actually exist, a statistical study has been carried out based on quality indicators data from the Technical University of Cartagena. Multiple linear regression has been used, through backward stepwise regression, to identify variables that may influence students’ opinions and to quantify their effects. The main result is that the variables analyzed, many of which are often cited as causes of bias, show little or no significant influence on student satisfaction with teaching. It is also important to remark that there are aspects of the teaching activity that can only be evaluated from the systematic observation made by students. Therefore, we believe that student surveys are an essential indicator, and their weight within teaching evaluation models should reflect their relevance.
Published: 2020

13. Search for Axionlike and Scalar Particles with the NA64 Experiment

Author: Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as shielding, and would be observed either through their $a(s)\to\gamma \gamma$ decay in the rest of the HCAL detector or as events with large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to $2.84\times10^{11}$ electrons on target allowing to set new limits on the $a(s)\gamma\gamma$-coupling strength for a(s) masses below 55 MeV., Comment: This publication is dedicated to the memory of our colleague Danila Tlisov. 7 pages, 5 figures, revised version accepted for publication in Phys. Rev. Lett
Published: 2020
Full Text: View/download PDF

14. Search for Axionlike and Scalar Particles with the NA64 Experiment

Author: Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as shielding, and would be observed either through their $a(s)\to\gamma \gamma$ decay in the rest of the HCAL detector or as events with large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to $2.84\times10^{11}$ electrons on target allowing to set new limits on the $a(s)\gamma\gamma$-coupling strength for a(s) masses below 55 MeV., Comment: This publication is dedicated to the memory of our colleague Danila Tlisov. 7 pages, 5 figures, revised version accepted for publication in Phys. Rev. Lett
Published: 2020
Full Text: View/download PDF

15. Search for Axionlike and Scalar Particles with the NA64 Experiment

Author: Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Sieber, H., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as shielding, and would be observed either through their $a(s)\to\gamma \gamma$ decay in the rest of the HCAL detector or as events with large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to $2.84\times10^{11}$ electrons on target allowing to set new limits on the $a(s)\gamma\gamma$-coupling strength for a(s) masses below 55 MeV., Comment: This publication is dedicated to the memory of our colleague Danila Tlisov. 7 pages, 5 figures, revised version accepted for publication in Phys. Rev. Lett
Published: 2020
Full Text: View/download PDF

16. Dark matter search in missing energy events with NA64

Author: Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: A search for sub-GeV dark matter production mediated by a new vector boson $A'$, called dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with $2.84\times10^{11}$ electrons on target no evidence of such a process has been found. The most stringent constraints on the $A'$ mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range $\lesssim 0.2$ GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search., Comment: 6 pages, 4 figures, version accepted for publication in Phys. Rev. Lett. arXiv admin note: text overlap with arXiv:1710.00971, arXiv:1610.02988
Published: 2019
Full Text: View/download PDF

17. Improved limits on a hypothetical X(16.7) boson and a dark photon decaying into $e^+e^-$ pairs

Author: Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: The improved results on a direct search for a new X(16.7 MeV) boson which could explain the anomalous excess of $e^+e^-$ pairs observed in the excited 8Be nucleus decays ("Berillium anomaly") are reported. Due to its coupling to electrons, the X boson could be produced in the bremsstrahlung reaction e-Z -> e-ZX by a high-energy beam of electrons incident on active target in the NA64 experiment at the CERN SPS and observed through its subsequent decay into $e^+e^-$ pair. No evidence for such decays was found from the combined analysis of the data samples with total statistics corresponding to 8.4\times 10^{10} electrons on target collected in 2017 and 2018. This allows to set the new limits on the $X$--$e^-$ coupling in the range 1.2 \times 10^{-4} < \epsilon_e < 6.8 \times 10^{-4}, excluding part of the parameter space favored by the Berillium anomaly. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay $A' \to e^+e^-$ of the bremsstrahlung A' with a mass below 24 MeV., Comment: 7 pages, 5 figures, 1 table. arXiv admin note: substantial text overlap with arXiv:1803.07748
Published: 2019
Full Text: View/download PDF

18. Dark matter search in missing energy events with NA64

Author: Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: A search for sub-GeV dark matter production mediated by a new vector boson $A'$, called dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with $2.84\times10^{11}$ electrons on target no evidence of such a process has been found. The most stringent constraints on the $A'$ mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range $\lesssim 0.2$ GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search., Comment: 6 pages, 4 figures, version accepted for publication in Phys. Rev. Lett. arXiv admin note: text overlap with arXiv:1710.00971, arXiv:1610.02988
Published: 2019
Full Text: View/download PDF

19. Improved limits on a hypothetical X(16.7) boson and a dark photon decaying into $e^+e^-$ pairs

Author: Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., Ulloa, P., Banerjee, D., Bernhard, J., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hoesgen, M., Jeckel, M., Kachanov, V. A., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kolosov, V. N., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Bueno, L. Molina, Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Shchukin, D., Tikhomirov, V. O., Tlisova, I., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V. Yu., and Ulloa, P.
Abstract: The improved results on a direct search for a new X(16.7 MeV) boson which could explain the anomalous excess of $e^+e^-$ pairs observed in the excited 8Be nucleus decays ("Berillium anomaly") are reported. Due to its coupling to electrons, the X boson could be produced in the bremsstrahlung reaction e-Z -> e-ZX by a high-energy beam of electrons incident on active target in the NA64 experiment at the CERN SPS and observed through its subsequent decay into $e^+e^-$ pair. No evidence for such decays was found from the combined analysis of the data samples with total statistics corresponding to 8.4\times 10^{10} electrons on target collected in 2017 and 2018. This allows to set the new limits on the $X$--$e^-$ coupling in the range 1.2 \times 10^{-4} < \epsilon_e < 6.8 \times 10^{-4}, excluding part of the parameter space favored by the Berillium anomaly. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay $A' \to e^+e^-$ of the bremsstrahlung A' with a mass below 24 MeV., Comment: 7 pages, 5 figures, 1 table. arXiv admin note: substantial text overlap with arXiv:1803.07748
Published: 2019
Full Text: View/download PDF

20. Search for a Hypothetical 16.7 MeV Gauge Boson and Dark Photons in the NA64 Experiment at CERN

Author: Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V., Ulloa, P., Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V., and Ulloa, P.
Abstract: We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e+e- pairs observed in the excited Be-8 nucleus decays. Due to its coupling to electrons, the X could be produced in the bremsstrahlung reaction e- Z -> e- Z X by a 100 GeV e- beam incident on an active target in the NA64 experiment at the CERN SPS and observed through the subsequent decay into an e+e- pair. With 5.4\times 10^{10} electrons on target, no evidence for such decays was found, allowing to set first limits on the X-e^- coupling in the range 1.3\times 10^{-4} < \epsilon_e < 4.2\times 10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay A'->e+e- of the bremsstrahlung A' with a mass <~ 23 MeV., Comment: 6 pages, 3 figures. Title changed as suggested by Journal; references added; version published in Phys. Rev. Lett
Published: 2018
Full Text: View/download PDF

21. Search for a Hypothetical 16.7 MeV Gauge Boson and Dark Photons in the NA64 Experiment at CERN

Author: Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V., Ulloa, P., Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dusaev, R. R., Enik, T., Charitonidis, N., Feshchenko, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Jeckel, M., Karneyeu, A. E., Kekelidze, G., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rojas, R., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Volkov, P. V., Volkov, V., and Ulloa, P.
Abstract: We report the first results on a direct search for a new 16.7 MeV boson (X) which could explain the anomalous excess of e+e- pairs observed in the excited Be-8 nucleus decays. Due to its coupling to electrons, the X could be produced in the bremsstrahlung reaction e- Z -> e- Z X by a 100 GeV e- beam incident on an active target in the NA64 experiment at the CERN SPS and observed through the subsequent decay into an e+e- pair. With 5.4\times 10^{10} electrons on target, no evidence for such decays was found, allowing to set first limits on the X-e^- coupling in the range 1.3\times 10^{-4} < \epsilon_e < 4.2\times 10^{-4} excluding part of the allowed parameter space. We also set new bounds on the mixing strength of photons with dark photons (A') from non-observation of the decay A'->e+e- of the bremsstrahlung A' with a mass <~ 23 MeV., Comment: 6 pages, 3 figures. Title changed as suggested by Journal; references added; version published in Phys. Rev. Lett
Published: 2018
Full Text: View/download PDF

22. Search for vector mediator of Dark Matter production in invisible decay mode

Author: NA64 Collaboration, Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Ulloa, P., NA64 Collaboration, Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, and Ulloa, P.
Abstract: A search is performed for a new sub-GeV vector boson ($A'$) mediated production of Dark Matter ($\chi$) in the fixed-target experiment, NA64, at the CERN SPS. The $A'$, called dark photon, could be generated in the reaction $ e^- Z \to e^- Z A'$ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay $A' \to \chi \overline{\chi}$. The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to $4.3\times10^{10}$ electrons on target no evidence of such a process has been found. New stringent constraints on the $A'$ mixing strength with photons, $10^{-5}\lesssim \epsilon \lesssim 10^{-2}$, for the $A'$ mass range $m_{A'} \lesssim 1$ GeV are derived. For models considering scalar and fermionic thermal Dark Matter interacting with the visible sector through the vector portal the 90% C.L. limits $10^{-11}\lesssim y \lesssim 10^{-6}$ on the dark-matter parameter $y = \epsilon^2 \alpha_D (\frac{m_\chi}{m_{A'}})^4 $ are obtained for the dark coupling constant $\alpha_D = 0.5$ and dark-matter masses $0.001 \lesssim m_\chi \lesssim 0.5 $ GeV. The lower limits $\alpha_D \gtrsim 10^{-3} $ for pseudo-Dirac Dark Matter in the mass region $m_\chi \lesssim 0.05 $ GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using tree level, exact calculations of the $A'$ production cross-sections, which turn out to be significantly smaller compared to the one obtained in the Weizs\"{a}cker-Williams approximation for the mass region $m_{A'} \gtrsim 0.1$ GeV., Comment: 22 pages, 17 figures, version accepted for publication in PRD
Published: 2017
Full Text: View/download PDF

23. Search for vector mediator of Dark Matter production in invisible decay mode

Author: NA64 Collaboration, Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, Ulloa, P., NA64 Collaboration, Banerjee, D., Burtsev, V. E., Chumakov, A. G., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gerassimov, S. G., Gninenko, S. N., Hosgen, M., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Konorov, I. V., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B. I., Arenas, G. Vasquez, and Ulloa, P.
Abstract: A search is performed for a new sub-GeV vector boson ($A'$) mediated production of Dark Matter ($\chi$) in the fixed-target experiment, NA64, at the CERN SPS. The $A'$, called dark photon, could be generated in the reaction $ e^- Z \to e^- Z A'$ of 100 GeV electrons dumped against an active target which is followed by the prompt invisible decay $A' \to \chi \overline{\chi}$. The experimental signature of this process would be an event with an isolated electron and large missing energy in the detector. From the analysis of the data sample collected in 2016 corresponding to $4.3\times10^{10}$ electrons on target no evidence of such a process has been found. New stringent constraints on the $A'$ mixing strength with photons, $10^{-5}\lesssim \epsilon \lesssim 10^{-2}$, for the $A'$ mass range $m_{A'} \lesssim 1$ GeV are derived. For models considering scalar and fermionic thermal Dark Matter interacting with the visible sector through the vector portal the 90% C.L. limits $10^{-11}\lesssim y \lesssim 10^{-6}$ on the dark-matter parameter $y = \epsilon^2 \alpha_D (\frac{m_\chi}{m_{A'}})^4 $ are obtained for the dark coupling constant $\alpha_D = 0.5$ and dark-matter masses $0.001 \lesssim m_\chi \lesssim 0.5 $ GeV. The lower limits $\alpha_D \gtrsim 10^{-3} $ for pseudo-Dirac Dark Matter in the mass region $m_\chi \lesssim 0.05 $ GeV are more stringent than the corresponding bounds from beam dump experiments. The results are obtained by using tree level, exact calculations of the $A'$ production cross-sections, which turn out to be significantly smaller compared to the one obtained in the Weizs\"{a}cker-Williams approximation for the mass region $m_{A'} \gtrsim 0.1$ GeV., Comment: 22 pages, 17 figures, version accepted for publication in PRD
Published: 2017
Full Text: View/download PDF

24. Performance of Multiplexed XY Resistive Micromegas detectors in a high intensity beam

Author: Banerjee, D., Burtsev, V., Chumakov, A., Cooke, D., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hösgen, M., Karneyeu, A. E., Ketzer, B., Kirsanov, M. M., Konorov, I. V., Kramarenko, V. A., Kuleshov, S. V., Levchenko, E., Lyubovitskij, V. E., Lysan, V., Mamon, S., Matveev, V. A., Mikhailov, Yu. V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Vasilishin, B., Arenas, G. Vasquez, Ulloa, P., Crivelli, P., Banerjee, D., Burtsev, V., Chumakov, A., Cooke, D., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hösgen, M., Karneyeu, A. E., Ketzer, B., Kirsanov, M. M., Konorov, I. V., Kramarenko, V. A., Kuleshov, S. V., Levchenko, E., Lyubovitskij, V. E., Lysan, V., Mamon, S., Matveev, V. A., Mikhailov, Yu. V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Vasilishin, B., Arenas, G. Vasquez, Ulloa, P., and Crivelli, P.
Abstract: We present the performance of multiplexed XY resistive Micromegas detectors tested in the CERN SPS 100 GeV/c electron beam at intensities up to 3.3 $\times$ 10$^5$ e$^- $/(s$\cdot$cm$^2$). So far, all studies with multiplexed Micromegas have only been reported for tests with radioactive sources and cosmic rays. The use of multiplexed modules in high intensity environments was not explored due to the effect of ambiguities in the reconstruction of the hit point caused by the multiplexing feature. At the beam intensities analysed in this work and with a multiplexing factor of 5, more than 50% level of ambiguity is introduced. Our results prove that by using the additional information of cluster size and integrated charge from the signal clusters induced on the XY strips, the ambiguities can be reduced to a level below 2%. The tested detectors are used in the CERN NA64 experiment for tracking the incoming particles bending in a magnetic field in order to reconstruct their momentum. The average hit detection efficiency of each module was found to be $\sim$ 96% at the highest beam intensities. By using four modules a tracking resolution of 1.1% was obtained with $\sim$ 85% combined tracking efficiency.
Published: 2017
Full Text: View/download PDF

25. High purity 100 GeV electron identification with synchrotron radiation

Author: Depero, E., Banerjee, D., Burtsev, V., Chumakov, A., Cooke, D., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hösgen, M., Karneyeu, A. E., Ketzer, B., Kirsanov, M. M., Konorov, I. V., Kramarenko, V. A., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Vasilishin, B., Arenas, G. Vasquez, Ulloa, P., Crivelli, P., Depero, E., Banerjee, D., Burtsev, V., Chumakov, A., Cooke, D., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hösgen, M., Karneyeu, A. E., Ketzer, B., Kirsanov, M. M., Konorov, I. V., Kramarenko, V. A., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Vasilishin, B., Arenas, G. Vasquez, Ulloa, P., and Crivelli, P.
Abstract: In high energy experiments such as active beam dump searches for rare decays and missing energy events, the beam purity is a crucial parameter. In this paper we present a technique to reject heavy charged particle contamination in the 100 GeV electron beam of the H4 beam line at CERN SPS. The method is based on the detection with BGO scintillators of the synchrotron radiation emitted by the electrons passing through a bending dipole magnet. A 100 GeV $\pi^-$ beam is used to test the method in the NA64 experiment resulting in a suppression factor of $10^{-5}$ while the efficiency for electron detection is $\sim$95%. The spectra and the rejection factors are in very good agreement with the Monte Carlo simulation. The reported suppression factors are significantly better than previously achieved., Comment: 10 pages, 6 figures
Published: 2017
Full Text: View/download PDF

26. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

27. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

28. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

29. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

30. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

31. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

32. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

33. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

34. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

35. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

36. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

37. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

38. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

39. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

40. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

41. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

42. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

43. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

44. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

45. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

46. Search for invisible decays of sub-GeV dark photons in missing-energy events at the CERN SPS

Author: NA64 Collaboration, Banerjee, D., Burtsev, V., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hosgen, M., Kachanov, V. A., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Petuhov, O., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B., Arenas, G. Vasquez, Ulloa, P., Zhukov, K., Zioutas, K., NA64 Collaboration, Banerjee, D., Burtsev, V., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hosgen, M., Kachanov, V. A., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Petuhov, O., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B., Arenas, G. Vasquez, Ulloa, P., Zhukov, K., and Zioutas, K.
Abstract: We report on a direct search for sub-GeV dark photons (A') which might be produced in the reaction e^- Z \to e^- Z A' via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The A's would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75\cdot 10^{9} electrons on target. We set new limits on the \gamma-A' mixing strength and exclude the invisible A' with a mass < 100 MeV as an explanation of the muon g_\mu-2 anomaly., Comment: 6 pages, 3 figures; Typos corrected, references added
Published: 2016
Full Text: View/download PDF

47. Proportional hazard birnbaum-saunders distribution with application to the survival data analysis [Distribución de riesgo proporcional Birnbaum-Saunders con aplicación al análisis de datos de supervivencia]

Author: Moreno-Arenas G., Martínez-Flórez G., Barrera-Causil C., Moreno-Arenas G., Martínez-Flórez G., and Barrera-Causil C.
Published: 2016

48. Search for invisible decays of sub-GeV dark photons in missing-energy events at the CERN SPS

Author: NA64 Collaboration, Banerjee, D., Burtsev, V., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hosgen, M., Kachanov, V. A., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Petuhov, O., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B., Arenas, G. Vasquez, Ulloa, P., Zhukov, K., Zioutas, K., NA64 Collaboration, Banerjee, D., Burtsev, V., Cooke, D., Crivelli, P., Depero, E., Dermenev, A. V., Donskov, S. V., Dubinin, F., Dusaev, R. R., Emmenegger, S., Fabich, A., Frolov, V. N., Gardikiotis, A., Gninenko, S. N., Hosgen, M., Kachanov, V. A., Karneyeu, A. E., Ketzer, B., Kirpichnikov, D. V., Kirsanov, M. M., Kovalenko, S. G., Kramarenko, V. A., Kravchuk, L. V., Krasnikov, N. V., Kuleshov, S. V., Lyubovitskij, V. E., Lysan, V., Matveev, V. A., Mikhailov, Yu. V., Myalkovskiy, V. V., Peshekhonov, V. D., Peshekhonov, D. V., Petuhov, O., Polyakov, V. A., Radics, B., Rubbia, A., Samoylenko, V. D., Tikhomirov, V. O., Tlisov, D. A., Toropin, A. N., Trifonov, A. Yu., Vasilishin, B., Arenas, G. Vasquez, Ulloa, P., Zhukov, K., and Zioutas, K.
Abstract: We report on a direct search for sub-GeV dark photons (A') which might be produced in the reaction e^- Z \to e^- Z A' via kinetic mixing with photons by 100 GeV electrons incident on an active target in the NA64 experiment at the CERN SPS. The A's would decay invisibly into dark matter particles resulting in events with large missing energy. No evidence for such decays was found with 2.75\cdot 10^{9} electrons on target. We set new limits on the \gamma-A' mixing strength and exclude the invisible A' with a mass < 100 MeV as an explanation of the muon g_\mu-2 anomaly., Comment: 6 pages, 3 figures; Typos corrected, references added
Published: 2016
Full Text: View/download PDF

49. Rumen microbial community composition varies with diet and host, but a core microbiome is found across a wide geographical range

Author: European Commission, Henderson, G., Cox, F., Ganesh, S., Jonker, A., Young, W., Janssen, P. H., Abecia, Leticia, Angarita, E., Aravena, P., Arenas, G. N., Ariza, C., Zhou, M., Witzig, M., Wright, A.-D. G., Yamano, H., Yan, T., Yáñez Ruiz, David R., Yeoman, C. J., Zhou, H. W., Zou, C. X., Zunino, P., Kelly, W. J., Barahona, R., Batistotti, M., Bertelsen, M. F., Jami, E., Brown-Kav, A., Carvajal, A. M., Cersosimo, L., Chaves, A. V., Church, J., Clipson, N., Guan, L. L., Cobos-Peralta, M. A., Cookson, A. L., Cravero, S., Carballo, O. C., Jelincic, J., Crosley, K., Cruz, Gustavo, Cucchi, M. C., De La Barra, R., De Menezes, A. B., Miri, V. H., Detmann, E., Dieho, K., Dijkstra, J., Dos Reis, W. L. S., Dugan, M. E. R., Kantanen, J., Ebrahimi, S. H., Eythórsdóttir, E., Fon, F. N., Fraga, M., Hernandez-Sanabria, E., Franco, F., Friedeman, C., Fukuma, N., Gagić , D., Gangnat, I., Grilli, D. J., Gomez, A. X. I., Isah, O. A., Ishaq, S., Kim, S.-H., Klieve, A., Kobayashi, Y., Parra, D., Koike, S., Kopecny, J., Kristensen, T. N., O'Neill, B., Krizsan, S. J., LaChance, H., Lachman, M., Lamberson, W. R., Lambie, S., Lassen, J., Muñoz, C., Leahy, S. C., Lee, S. S., Leiber, F., Lewis, E., Ospina, S., Lin, B., Lira, R., Lund, P., Macipe, E., Mamuad, L. L., Murovec, B., Mantovani, H. C., Marcoppido, G. A., Márquez, C., Martín, C., Martínez-Fernández, Gonzalo, Ouwerkerk, D., Martínez, M. E., Mayorga, O. L., McAllister, T. A., McSweeney, C., Newbold, C. Jamie, Mestre, L., Minnee, E., Mitsumori, M., Mizrahi, I., Molina, I., Muenger, A., Nsereko, V., O'Donovan, M., Okunade, S., Pereira, L. G. R., Pinares-Patino, C., Pope, P. B., Bannink, A., Poulsen, M., Rodehutscord, M., Rodríguez, T., Attwood, G. T., Saito, K., Sales, F., Sauer, C., Shingfield, K. J., Shoji, N., Simunek, J., Zambrano, R., Stojanović -Radić, Z., Stres, B., Sun, X., Swartz, J., Ávila, J. M., Tan, Z. L., Tapio, I., Taxis, T. M., Tomkins, N., Ungerfeld, E., Zeitz, J., Valizadeh, R., Van Adrichem, P., van Hamme, J., Van Hoven, W., Waghorn, G., Avila-Stagno, J., Wallace, R. J., Wang, M., Waters, S. M., Keogh, K., European Commission, Henderson, G., Cox, F., Ganesh, S., Jonker, A., Young, W., Janssen, P. H., Abecia, Leticia, Angarita, E., Aravena, P., Arenas, G. N., Ariza, C., Zhou, M., Witzig, M., Wright, A.-D. G., Yamano, H., Yan, T., Yáñez Ruiz, David R., Yeoman, C. J., Zhou, H. W., Zou, C. X., Zunino, P., Kelly, W. J., Barahona, R., Batistotti, M., Bertelsen, M. F., Jami, E., Brown-Kav, A., Carvajal, A. M., Cersosimo, L., Chaves, A. V., Church, J., Clipson, N., Guan, L. L., Cobos-Peralta, M. A., Cookson, A. L., Cravero, S., Carballo, O. C., Jelincic, J., Crosley, K., Cruz, Gustavo, Cucchi, M. C., De La Barra, R., De Menezes, A. B., Miri, V. H., Detmann, E., Dieho, K., Dijkstra, J., Dos Reis, W. L. S., Dugan, M. E. R., Kantanen, J., Ebrahimi, S. H., Eythórsdóttir, E., Fon, F. N., Fraga, M., Hernandez-Sanabria, E., Franco, F., Friedeman, C., Fukuma, N., Gagić , D., Gangnat, I., Grilli, D. J., Gomez, A. X. I., Isah, O. A., Ishaq, S., Kim, S.-H., Klieve, A., Kobayashi, Y., Parra, D., Koike, S., Kopecny, J., Kristensen, T. N., O'Neill, B., Krizsan, S. J., LaChance, H., Lachman, M., Lamberson, W. R., Lambie, S., Lassen, J., Muñoz, C., Leahy, S. C., Lee, S. S., Leiber, F., Lewis, E., Ospina, S., Lin, B., Lira, R., Lund, P., Macipe, E., Mamuad, L. L., Murovec, B., Mantovani, H. C., Marcoppido, G. A., Márquez, C., Martín, C., Martínez-Fernández, Gonzalo, Ouwerkerk, D., Martínez, M. E., Mayorga, O. L., McAllister, T. A., McSweeney, C., Newbold, C. Jamie, Mestre, L., Minnee, E., Mitsumori, M., Mizrahi, I., Molina, I., Muenger, A., Nsereko, V., O'Donovan, M., Okunade, S., Pereira, L. G. R., Pinares-Patino, C., Pope, P. B., Bannink, A., Poulsen, M., Rodehutscord, M., Rodríguez, T., Attwood, G. T., Saito, K., Sales, F., Sauer, C., Shingfield, K. J., Shoji, N., Simunek, J., Zambrano, R., Stojanović -Radić, Z., Stres, B., Sun, X., Swartz, J., Ávila, J. M., Tan, Z. L., Tapio, I., Taxis, T. M., Tomkins, N., Ungerfeld, E., Zeitz, J., Valizadeh, R., Van Adrichem, P., van Hamme, J., Van Hoven, W., Waghorn, G., Avila-Stagno, J., Wallace, R. J., Wang, M., Waters, S. M., and Keogh, K.
Abstract: © 2015 Macmillan Publishers Limited. Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrence patterns between microbes, suggesting that major metabolic interactions are non-selective rather than specific.
Published: 2015

50. Systemic Analysis of service and financial risks in a supply chain

Author: Romo L., Felipe, Daza, Harold F., Arenas G., Fernando A., Romo L., Felipe, Daza, Harold F., and Arenas G., Fernando A.
Abstract: Based on a model developed trough system dynamics, which represents a supply chain, this paper aims to establish a systemic approach to service risk management and financial risk management, taking into account the decisions made from the operational area and its influence on the risk in different areas of the company., Partiendo de un modelo desarrollado por medio de la dinámica de sistemas, que representa una cadena de abastecimiento, este trabajo tiene como finalidad establecer una aproximación sistémica a la gestión de los riesgos de servicio y financiero, teniendo en cuenta la toma de decisiones desde el área operativa y su influencia sobre el riesgo en otras áreas de la empresa.
Published: 2013

Catalog

Books, media, physical & digital resources

See catalog results

Searchworks

Select search scope, currently: Articles Catalog books, media & more in Jio Institute collections Articles journal articles & other e-resources

Search

Search Constraints

Refine your results

Search Limiters

Publication Year Range

Publication Type

Database

Publisher

61 results on '"Arenas G"'

Search Results

Catalog

Select search scope, currently: Articles

Catalog

books, media & more in Jio Institute collections

Articles

journal articles & other e-resources