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1. A search for $\mu^+\to e^+\gamma$ with the first dataset of the MEG II experiment

Author

MEG II collaboration, Afanaciev, K., Baldini, A. M., Ban, S., Baranov, V., Benmansour, H., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiappini, M., Chiarello, G., Corvaglia, A., Cuna, F., Maso, G. Dal, De Bari, A., De Gerone, M., Barusso, L. Ferrari, Francesconi, M., Galli, L., Gallucci, G., Gatti, F., Gerritzen, L., Grancagnolo, F., Grandoni, E. G., Grassi, M., Grigoriev, D. N., Hildebrandt, M., Ieki, K., Ignatov, F., Ikeda, F., Iwamoto, T., Karpov, S., Kettle, P. -R., Khomutov, N., Kobayashi, S., Kolesnikov, A., Kravchuk, N., Krylov, V., Kuchinskiy, N., Kyle, W., Libeiro, T., Malyshev, V., Matsushita, A., Meucci, M., Mihara, S., Molzon, W., Mori, Toshinori, Nakao, M., Nicolò, D., Nishiguchi, H., Ochi, A., Ogawa, S., Onda, R., Ootani, W., Oya, A., Palo, D., Panareo, M., Papa, A., Pettinacci, V., Popov, A., Renga, F., Ritt, S., Rossella, M., Rozhdestvensky, A., Schwendimann, P., Shimada, K., Signorelli, G., Takahashi, M., Tassielli, G. F., Toyoda, K., Uchiyama, Y., Usami, M., Venturini, A., Vitali, B., Voena, C., Yamamoto, K., Yanai, K., Yonemoto, T., Yoshida, K., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

The MEG II experiment, based at the Paul Scherrer Institut in Switzerland, reports the result of a search for the decay $\mu^+\to e^+\gamma$ from data taken in the first physics run in 2021. No excess of events over the expected background is observed, yielding an upper limit on the branching ratio of B($\mu^+\to e^+\gamma$) < $7.5 \times 10^{-13}$ (90% C.L.). The combination of this result and the limit obtained by MEG gives B($\mu^+\to e^+\gamma$) < $3.1 \times 10^{-13}$ (90% C.L.), which is the most stringent limit to date. A ten-fold larger sample of data is being collected during the years 2022-2023, and data-taking will continue in the coming years., Comment: 10 pages, 6 figures. To be published in EPJC

Published
2023

2. Performances of a new generation tracking detector: the MEG II cylindrical drfit chamber

Author

Baldini, A. M., Benmansour, H., Boca, G., Cavoto, G., Cei, F., Chiappini, M., Chiarello, G., Corvaglia, A., Cuna, F., Francesconi, M., Galli, L., Grancagnolo, F., Grandoni, E. G., Grassi, M., Hildebrandt, M., Ignatov, F., Meucci, M., Molzon, W., Nicolo', D., Oya, A., Palo, D., Panareo, M., Papa, A., Raffaelli, F., Renga, F., Signorelli, G., Tassielli, G. F., Uchiyama, Y., Venturini, A., Vitali, B., and Voena, C.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The cylindrical drift chamber is the most innovative part of the MEG~II detector, the upgraded version of the MEG experiment. The MEG~II chamber differs from the MEG one because it is a single volume cylindrical structure, instead of a segmented one, chosen to improve its resolutions and efficiency in detecting low energy positrons from muon decays at rest. In this paper, we show the characteristics and performances of this fundamental part of the MEG~II apparatus and we discuss the impact of its higher resolution and efficiency on the sensitivity of the MEG~II experiment. Because of its innovative structure and high quality resolution and efficiency the MEG~II cylindrical drift chamber will be a cornerstone in the development of an ideal tracking detector for future positron-electron collider machines., Comment: 27 pages, 42 figures, published on EPJC 84(2024)5,473

Published
2023

3. Operation and performance of MEG II detector

Author

MEG II Collaboration, Afanaciev, K., Baldini, A. M., Ban, S., Baranov, V., Benmansour, H., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiappini, M., Chiarello, G., Corvaglia, A., Cuna, F., Maso, G. Dal, De Bari, A., De Gerone, M., Barusso, L. Ferrari, Francesconi, M., Galli, L., Gallucci, G., Gatti, F., Gerritzen, L., Grancagnolo, F., Grandoni, E. G., Grassi, M., Grigoriev, D. N., Hildebrandt, M., Ieki, K., Ignatov, F., Ikeda, F., Iwamoto, T., Karpov, S., Kettle, P. -R., Khomutov, N., Kobayashi, S., Kolesnikov, A., Kravchuk, N., Krylov, V., Kuchinskiy, N., Kyle, W., Libeiro, T., Malyshev, V., Matsushita, A., Meucci, M., Mihara, S., Molzon, W., Mori, Toshinori, Morsani, F., Nakao, M., Nicolò, D., Nishiguchi, H., Ochi, A., Ogawa, S., Onda, R., Ootani, W., Oya, A., Palo, D., Panareo, M., Papa, A., Pettinacci, V., Popov, A., Raffaelli, F., Renga, F., Ritt, S., Rossella, M., Rozhdestvensky, A., Schwendimann, P., Shimada, K., Signorelli, G., Stoykov, A., Takahashi, M., Tassielli, G. F., Toyoda, K., Uchiyama, Y., Usami, M., Venturini, A., Vitali, B., Voena, C., Yamamoto, K., Yanai, K., Yonemoto, T., Yoshida, K., and Yudin, Yu. V.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The MEG II experiment, located at the Paul Scherrer Institut (PSI) in Switzerland, is the successor to the MEG experiment, which completed data taking in 2013. MEG II started fully operational data taking in 2021, with the goal of improving the sensitivity of the mu+ -> e+ gamma decay down to 6e-14 almost an order of magnitude better than the current limit. In this paper, we describe the operation and performance of the experiment and give a new estimate of its sensitivity versus data acquisition time., Comment: 42 pages, 55 figures. Submitted to EPJC

Published
2023

4. Measurement of the pion form factor with CMD-3 detector and its implication to the hadronic contribution to muon (g-2)

Author

Collaboration, CMD-3, Ignatov, F. V., Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Bashtovoy, N. S., Berkaev, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Fedotovich, G. V., Gorkovenko, A. O., Grancagnolo, F. J., Grebenuk, A. A., Gribanov, S. S., Grigoriev, D. N., Ivanov, V. L., Karpov, S. V., Kasaev, A. S., Kazanin, V. F., Khazin, B. I., Kirpotin, A. N., Koop, I. A., Korobov, A. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Lysenko, A. P., Mikhailov, K. Yu., Obraztsov, I. V., Okhapkin, V. S., Otboev, A. V., Perevedentsev, E. A., Pestov, Yu. N., Popov, A. S., Razuvaev, G. P., Rogovsky, Yu. A., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Semenov, A. V., Senchenko, A. I., Shatunov, P. Yu., Shatunov, Yu. M., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Solodov, E. P., Talyshev, A. A., Timoshenko, M. V., Titov, V. M., Tolmachev, S. S., Vorobiov, A. I., Yudin, Yu. V., Zemlyansky, I. M., Zhadan, D. S., Zharinov, Yu. M., and Zubakin, A. S.

Subjects
High Energy Physics - Experiment
Abstract

The cross section of the process $e^+e^-\to\pi^+\pi^-$ has been measured in the center-of-mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on an integrated luminosity of about 88 pb$^{-1}$, of which 62 pb$^{-1}$ represent a complete dataset collected by CMD-3 at center-of-mass energies below 1 GeV. In the dominant region near the $\rho$ resonance a systematic uncertainty of 0.7% was achieved. The implications of the presented results for the evaluation of the hadronic contribution to the anomalous magnetic moment of the muon are discussed., Comment: 8 pages, 3 figures; as published in Phys. Rev. Lett. 132, 231903

Published
2023
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5. Study of π+π−π+π− production with CMD-3 detector at the VEPP-2000 collider

Author

Korobov A. A., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Aulchenko V. M., Banzarov V. Sh., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Fedotovich G. V., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ignatov F. V., Ivanov V. L., Karpov S. V., Kasaev A. S., Kazanin V. F., Koop I. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lysenko A. P., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., Otboev A. V., Perevedentsev E. A., Pestov Yu. N., Popov A. S., Razuvaev G. P., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Semenov A. V., Senchenko A. I., Shatunov Yu. M., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Solodov E. P., Titov V. M., Talyshev A. A., Vorobiov A. I., and Yudin Yu. V.

Subjects
Physics, QC1-999
Abstract

The cross section of the process e+e−→ π+π−π+π− has been measured using an integrated luminosity of 17 pb−1 collected with the CMD-3 detector in the center-of-mass energy range 650-1000 MeV. High-precision measurements of various hadronic cross sections are of great interest in relation with the problem of the muon anomalous magnetic moment g-2. This measurement can be also used to test the relation between the cross section of e+e−→ π+ π−π+ π− and the spectral function for the τ−→ π−π0π0π0 decay predicted by the conservation of vector current (CVC).

Published
2019
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6. Study of the process e+e−→ K+K−π0 in the center-of-mass energy range 1.2–2 GeV with the CMD-3 detector

Author

Erofeev A. L., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Aulchenko V. M., Banzarov V. Sh., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Fedotovich G. V., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ignatov F. V., Ivanov V. L., Karpov S. V., Kasaev A. S., Kazanin V. F., Koop I. A., Korobov A. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lysenko A. P., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., Otboev A. V., Perevedentsev E. A., Pestov Yu. N., Popov A. S., Razuvaev G. P., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Semenov A. V., Senchenko A. I., Shatunov Yu. M., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Solodov E. P., Titov V. M., Talyshev A. A., Vorobiov A. I., and Yudin Yu. V.

Subjects
Physics, QC1-999
Abstract

The process e+ e−→ K+ K−π0 has been studied in the center-of-mass energy range from 1.2 to 2 GeV using a 80.6 pb−1 data sample collected with the CMD-3 detector at the electron-positron collider VEPP-2000. Preliminary results of the cross-section measurement are presented.

Published
2019
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7. Search for the process e+e−→D*(2007) with the CMD-3 detector

Author

Shemyakin D. N., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Aulchenko V. M., Banzarov V. Sh., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Fedotovich G. V., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ignatov F. V., Ivanov V. L., Karpov S. V., Kasaev A. S., Kazanin V. F., Koop I. A., Korobov A. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lysenko A. P., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., Otboev A. V., Perevedentsev E. A., Pestov Yu. N., Popov A. S., Razuvaev G. P., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Semenov A. V., Senchenko A. I., Shatunov Yu. M., Shebalin V. E., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Solodov E. P., Titov V. M., Talyshev A. A., Tolmachev S. S., Vorobiov A. I., and Yudin Yu. V.

Subjects
Physics, QC1-999
Abstract

A search for the process e+e−→ D*0(2007) has been performed with the CMD-3 detector at the VEPP-2000 e+e−-collider. Two main decay modes of the D*0(2007) decay, D0π0 and D0γ, followed by D0 → K+π−π+π−are used in this analysis. With an integrated luminosity of 3.7 pb−1 collected at the center-of-mass energy Ec.m. =2006.62 MeV our preliminary upper limit is BD*0→e+ e−

Published
2019
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8. Simulation of physics background in Super c-tau factory detector

Author

Shekhtman L, Ignatov F, and Tayursky V

Subjects
Physics, QC1-999
Abstract

Simulation of background particle fluxes generated by colliding beams is performed with FLUKA package for the Super C-Tau factory Detector (SCTD). Two processes are considered as main sources of luminosity generated background: two-photon production of electron-positron pairs and Bha-Bha scattering with bremsstrahlung photon emission (radiative Bha-Bha). The SCTD geometry is described corresponding to the last version of the Conceptual Design Report. The magnetic field based on the calculation in ANSYS is introduced in the model. Main results of the simulation for beam energy of 3 GeV, luminosity of 1035 cm−2s−1 and 1.5 T magnetic field are the following: charged particle fluence in the region of the Inner Tracker (radius 5cm -20 cm, Z between -30cm and 30 cm) is between 105 particles/(cm2s) and ∼103 particles/(cm2s); 1-MeV neutron equivalent fluence for Si in the regions corresponding to electronics of the Inner Tracker and the Drift Chamber is below 1011 n/(cm2y) and absorbed dose is below 100 Gy/y in the hottest regions of the detector.

Published
2019
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9. Study of the process e+e-→π+π-γ with the CMD-3 detector at the e+e- collider VEPP-2000

Author

Tolmachev S. S., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Aulchenko V. M., Banzarov V. Sh., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Fedotovich G. V., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ignatov F. V., Ivanov V. L., Karpov S. V., Kazanin V. F., Kirpotin A. N., Koop I. A., Korobov A. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., Pestov Yu. N., Popov A. S., Razuvaev G. P., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Semenov A. V., Shatunov Yu. M., Shatunov P. Yu., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Solodov E. P., Titov V. M., Talyshev A. A., Vorobiov A. I., Zemlyansky I. M., and Yudinl Yu. V.

Subjects
Physics, QC1-999
Abstract

Existing Monte-Carlo generators with radiative corrections to the e+e-→π+π- process are usually developed under the assumption that pions can be treated as pointlike particles. We study the e+e-→π+π-γ process with final-state radiation and test this assumption using simulated events from the MCGPJ generator based on the scalar QED hypothesis. In order to increase a fraction of events with FSR, the analysis was performed in the energy region to the left from the ρ-meson peak (660÷785 MeV) that is based on the integrated luminosity of about 8.4 pb-1. The experimental data for the photon energy spectrum agree with the simulation results at 1% level.

Published
2019
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10. The NNbar and multihadron production at the threshold at VEPP2000

Author

Solodov E. P., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Aulchenko V. M., Banzarov V. Sh., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Fedotovich G. V., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ignatov F. V., Ivanov V. L., Karpov S. V., Kazanin V. F., Koop I. A., Kirpotin A. N., Korobov A. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., Pestov Yu. N., Popov A. S., Razuvaev G. P., Rogovsky Yu. A., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Semenov A. V., Shatunov Yu. M., Shatunov P. Yu., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Titov V. M., Talyshev A. A., Vorobiov A. I., Zemlyansky I. M., and Yudin Yu. V.

Subjects
Physics, QC1-999
Abstract

A study of hadron production at the nucleon-antinucleon threshold has been performed with the CMD-3 detector at the VEPP-2000 e+e− collider. A very fast rise with an about 1 MeV width has been observed in the e+e−→ pp̅ cross section. A sharp drop in the e+ e−→ 3(π+π−) cross section has been con?rmed and found to have a width of less than 2 MeV, in agreement with the observed fast rise of the e+e−→ pp̅ cross section. For the ?rst time a similar sharp drop is demonstrated in the e+e−→ K+ K−π+π− cross section. The behavior of the e+e−→ 3(π+ π−), K+ K−π+π− cross sections cannot be explained by an interference of any resonance amplitude with continuum, therefore this phenomenon cannot be due to a narrow near-threshold resonance. No such structure has been observed in the e+e−→ 2(π+π−) cross section.

Published
2019
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11. Recent results from CMD-3

Author

Ignatov F. V., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Aulchenko V. M., Banzarov V. Sh., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Fedotovich G. V., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ivanov V. L., Karpov S. V., Kazanin V. F., Koop I. A., Kirpotin A. N., Korobov A. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., Pestov Yu. N., Popov A. S., Razuvaev G. P., Rogovsky Yu. A., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Semenov A. V., Shatunov Yu. M., Shatunov P. Yu., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Solodov E. P., Titov V. M., Talyshev A. A., Vorobiov A. I., Zemlyansky I. M., and Yudin Yu. V.

Subjects
Physics, QC1-999
Abstract

Regular data taking with the CMD-3 at the electron-positron collider VEPP-2000 is under way since 2010. The collected data sample corresponds to about 200 inverse picobarns of integrated luminosity per detector in the energy range from 0.32 up to 2 GeV, with a goal to collect about 1 fb−1 during next five years. Some of the recent results from the CMD-3 detector are discussed.

Published
2019
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12. Study of the e+e−→ KS KLπ0 process up to 2 GeV with the CMD-3 detector at the VEPP-2000 collider

Author

Semenov A. V., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Aulchenko V. M., Banzarov V. Sh., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Fedotovich G. V., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ignatov F. V., Ivanov V. L., Karpov S. V., Kazanin V. F., Koop I. A., Kirpotin A. N., Korobov A. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., Pestov Yu. N., Popov A. S., Razuvaev G. P., Rogovsky Yu. A., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Shatunov Yu. M., Shatunov P. Yu., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Solodov E. P., Titov V. M., Talyshev A. A., Vorobiov A. I., Zemlyansky I. M., and Yudin Yu. V.

Subjects
Physics, QC1-999
Abstract

The cross section of the process e+ e−→ KS KL π0 has been studied with the CMD-3 detector at the VEPP-2000 electron-positron collider in the center-of-mass energy range from 1.1 to 2 GeV. Preliminary results on the total cross section of the process are presented.

Published
2019
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13. An amplitude analysis of the process e+e-→ 4π in the center-of-mass energy range 900–2000 MeV with the CMD3 detector at the VEPP-2000 e+e- collider

Author

Kozyrev E. A., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Aulchenko V. M., Banzarov V. Sh., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Fedotovich G. V., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ignatov F. V., Ivanov V. L., Karpov S. V., Kazanin V. F., Koop I. A., Kirpotin A. N., Korobov A. A., Kozyrev A. N., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., Pestov Yu. N., Popov A. S., Razuvaev G. P., Rogovsky Yu. A., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Semenov A. V., Shatunov Yu. M., Shatunov P. Yu., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Solodov E. P., Titov V. M., Talyshev A. A., Vorobiov A. I., Zemlyansky I. M., and Yudin Yu. V.

Subjects
Physics, QC1-999
Abstract

A large data sample of e+e-→ 4π collected by the CMD-3 experiment at the VEPP-2000 e+ e− collider allowed for an amplitude analysis of the process e+e−→ 4π in the center-of-mass energy range 900–2000 MeV. Various intermediate components were distinguished and dominance of the ωπ0 and a1π amplitudes has been proved.

Published
2019
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14. Recent results of the hadronic cross section measurements with the CMD-3 detector at e+e− collider VEPP-2000

Author

Fedotovich G. V., Akhmetshin R. R., Amirkhanov A. N., Anisenkov A. V., Banzarov V. S., Bashtovoy N. S., Berkaev D. E., Bondar A. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Gayazov S. E., Grebenuk A. A., Gribanov S. S., Grigoriev D. N., Ignatov F. V., Ivanov V. L., Karpov S. V., Kazanin V. F., Kirpotin A. N., Koop I. A., Korobov A. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lukin P. A., Mikhailov K. Yu., Okhapkin V. S., OTBOEV A. V., Peatov Yu. N., Popov A. S., Razuvaev G. P., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Stnchenko A. I., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Shatunov P. Yu., Shatunov Yu. M., Solodov E. P., Talyshev A. A., Titov V. M., Tolmachev S. S., Vorobiov A. I., Zemlyansky I. M., and Yudin Yu. V.

Subjects
Physics, QC1-999
Abstract

A brief review of the recent results on the hadronic cross section measurements with the CMD-3 detector at the e+e− collider VEPP-2000 is given. Focus is made on the processes with charged kaons in multihadron events, which have a strong impact on strange meson spectroscopy and form factors that are important ingredients in the Dalitz plot analysis. Experimental data relevant to the topic are presented from the broad energy range covered by VEPP-2000 and compared to earlier measurements by the different collaborations. The analysis is based on the integrated luminosity of about 100 pb−1 collected in 2011, 2012 and 2017.

Published
2019
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15. Measurement of the $e^+e^-\to\pi^+\pi^-$ cross section from threshold to 1.2 GeV with the CMD-3 detector

Author

Collaboration, CMD-3, Ignatov, F. V., Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Bashtovoy, N. S., Berkaev, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Fedotovich, G. V., Gorkovenko, A. O., Grancagnolo, F. J., Grebenuk, A. A., Gribanov, S. S., Grigoriev, D. N., Ivanov, V. L., Karpov, S. V., Kasaev, A. S., Kazanin, V. F., Khazin, B. I., Kirpotin, A. N., Koop, I. A., Korobov, A. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Lysenko, A. P., Mikhailov, K. Yu., Obraztsov, I. V., Okhapkin, V. S., Otboev, A. V., Perevedentsev, E. A., Pestov, Yu. N., Popov, A. S., Razuvaev, G. P., Rogovsky, Yu. A., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Semenov, A. V., Senchenko, A. I., Shatunov, P. Yu., Shatunov, Yu. M., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Solodov, E. P., Talyshev, A. A., Timoshenko, M. V., Titov, V. M., Tolmachev, S. S., Vorobiov, A. I., Zemlyansky, I. M., Zhadan, D. S., Zharinov, Yu. M., Zubakin, A. S., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

The cross section of the process $e^+e^-\to\pi^+\pi^-$ has been measured in the center of mass energy range from 0.32 to 1.2 GeV with the CMD-3 detector at the electron-positron collider VEPP-2000. The measurement is based on a full dataset collected below 1 GeV during three data taking seasons, corresponding to an integrated luminosity of about 62 pb$^{-1}$. In the dominant $\rho$-resonance region, a systematic uncertainty of 0.7% has been reached. At energies around $\phi$-resonance the $\pi^+\pi^-$ production cross section was measured for the first time with high beam energy resolution. The forward-backward charge asymmetry in the $\pi^+\pi^-$ production has also been measured. It shows a strong deviation from the theoretical prediction based on the conventional scalar quantum electrodynamics framework, and it is in good agreement with the generalized vector-meson-dominance and dispersive-based predictions. The impact of the presented results on the evaluation of the hadronic contribution to the anomalous magnetic moment of muon is discussed., Comment: 54 pages, 36 figures; as published in Phys. Rev. D 109, 112002

Published
2023
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16. Performances of a new generation tracking detector: the MEG II cylindrical drift chamber

Author

Baldini, A. M., Benmansour, H., Boca, G., Cavoto, G., Cei, F., Chiappini, M., Chiarello, G., Corvaglia, A., Cuna, F., Francesconi, M., Galli, L., Grancagnolo, F., Grandoni, E. G., Grassi, M., Hildebrandt, M., Ignatov, F., Meucci, M., Molzon, W., Nicolò, D., Oya, A., Palo, D., Panareo, M., Papa, A., Raffaelli, F., Renga, F., Signorelli, G., Tassielli, G. F., Uchiyama, Y., Venturini, A., Vitali, B., and Voena, C.

Published
2024
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17. A search for μ+→e+γ with the first dataset of the MEG II experiment

Author

Afanaciev, K., Baldini, A. M., Ban, S., Baranov, V., Benmansour, H., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiappini, M., Chiarello, G., Corvaglia, A., Cuna, F., Maso, G. Dal, De Bari, A., De Gerone, M., Barusso, L. Ferrari, Francesconi, M., Galli, L., Gallucci, G., Gatti, F., Gerritzen, L., Grancagnolo, F., Grandoni, E. G., Grassi, M., Grigoriev, D. N., Hildebrandt, M., Ieki, K., Ignatov, F., Ikeda, F., Iwamoto, T., Karpov, S., Kettle, P.-R., Khomutov, N., Kobayashi, S., Kolesnikov, A., Kravchuk, N., Krylov, V., Kuchinskiy, N., Kyle, W., Libeiro, T., Malyshev, V., Matsushita, A., Meucci, M., Mihara, S., Molzon, W., Mori, Toshinori, Nakao, M., Nicolò, D., Nishiguchi, H., Ochi, A., Ogawa, S., Onda, R., Ootani, W., Oya, A., Palo, D., Panareo, M., Papa, A., Pettinacci, V., Popov, A., Renga, F., Ritt, S., Rossella, M., Rozhdestvensky, A., Schwendimann, P., Shimada, K., Signorelli, G., Takahashi, M., Tassielli, G. F., Toyoda, K., Uchiyama, Y., Usami, M., Venturini, A., Vitali, B., Voena, C., Yamamoto, K., Yanai, K., Yonemoto, T., Yoshida, K., and Yudin, Yu. V.

Published
2024
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18. Alignment of the MEG II cylindrical drift chamber

Author

Venturini, A., Baldini, A.M., Benmansour, H., Bianco, L., Boca, G., Brini, M., Cavoto, G., Cei, F., Chiappini, M., Francesconi, M., Galli, L., Gallucci, G., Grancagnolo, F., Grandoni, E.G., Grassi, M., Hildebrandt, M., Ignatov, F., Leonetti, F., Nicolò, D., Oya, A., Panareo, M., Papa, A., Renga, F., Uchiyama, Y., and Voena, C.

Published
2024
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19. Mini-Proceedings of the STRONG2020 Virtual Workshop on 'Space-like and Time-like determination of the Hadronic Leading Order contribution to the Muon $g-2$'

Author

Abbiendi, G., Arbuzov, A., Banerjee, Sw., Biswas, D., Budassi, E., Colangelo, G., Czyż, H., Davier, M., Denig, A., Driutti, A., Engel, T., Gagliardi, G., Hoferichter, M., Ignatov, F., Jadach, S., Komijani, J., Kupść, A., Laporta, S., Lusiani, A., Malaescu, B., Mandal, M. K., Marconi, U., Marinković, M. K., Mattiazzi, L., Müller, S. E., Nesterenko, A. V., Passera, M., Przedzinski, T., Ronca, J., Teubner, T., Bobadilla, W. J. Torres, Venanzoni, G., Was, Z., and Zhou, X.

Subjects
High Energy Physics - Phenomenology, High Energy Physics - Experiment
Abstract

The mini-proceedings of the STRONG2020 Virtual Workshop "Space-like and Time-like determination of the Hadronic Leading Order contribution to the Muon $g-2$", November 24--26 2021, are presented. This is the first workshop of the STRONG2020 WP21: JRA3-PrecisionSM: Precision Tests of the Standard Model (http://www.strong-2020.eu/joint-research-activity/jra3-precisionsm.html). The workshop was devoted to review of the working group activitity on: $(\it i)$ Radiative Corrections and Monte Carlo tools for low-energy hadronic cross sections in $e^+ e^-$ collisions; $(\it ii)$ Annotated database for $e^+e^-$ into hadrons processes at low energy; $(\it iii)$ Radiative Corrections and Monte Carlo tools for $\mu$-$e$ elastic scattering., Comment: 43 pages, 21 contributions. Editors: A. Kup\'s\'c and G. Venanzoni

Published
2022

20. Overview of the CMD-3 recent results at e+e− collider VEPP-2000

Author

Fedotovich G. V., Akhmetshin R. R., Anisenkov A. V., Aulchenko V. M., Banzarov V. S., Bashtovoy N. S., Berkaev D. E., Bragin A. V., Eidelman S. I., Epifanov D. A., Epshteyn L. B., Erofeev A. L., Gayazov S. E., Grebenuk A. A., Grigoriev D. N., Gromov E. M., Ignatov F. V., Ivanov V. L., Karpov S. V., Kazanin V. F., Khazin B. I., Kirpotin A. N., Koop I. A., Kovalenko O. A., Kozyrev A. N., Kozyrev E. A., Krokovny P. P., Kuzmenko A. E., Kuzmin A. S., Logashenko I. B., Lukin P. A., Lysenko A. P., Mikhailov K. Yu., Okhapkin V. S., Pestov Yu. N., Perevedentsev E. A., Popov A. S., Razuvaev G. P., Rogovsky Yu. A., Romanov A. L., Ruban A. A., Ryskulov N. M., Ryzhenenkov A. E., Shebalin V. E., Shemyakin D. N., Shwartz B. A., Shwartz D. B., Sibidanov A. L., Shatunov P. Yu., Shatunov Yu. M., Solodov E. P., Titov V. M., Talyshev A. A., Vorobiov A. I., Yudin Yu. V., and Zharinov Yu. M.

Subjects
Physics, QC1-999
Abstract

Since December 2010, the CMD-3 detector has collected data at the electronpositron collider VEPP-2000. The sample of the accumulated data corresponds to about 60 pb−1 of integrated luminosity in the c.m. energy from 0.32 up to 2 GeV. Preliminary results of the analysis of various processes e+e− annihilation to hadrons are presented. It is shown the processes with multihadron events have several intermediate states which must be taken into account to correctly describe the angular and invariant mass distributions as well as cross section dependence versus energy.

Published
2016
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21. An Experiment Exploring Gravitational Effects on CP Violation

Author

Piacentino, G. M., Palladino, A., Pilato, R. N., Venanzoni, G., Conti, L., Di Sciacio, G., Di Stefano, R., Fratianni, N., Gioiosa, A., Hajdukovic, D., Ignatov, F., Marignetti, F., and Testa, V.

Subjects
High Energy Physics - Phenomenology, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, General Relativity and Quantum Cosmology, High Energy Physics - Experiment
Abstract

We suggest a new experiment sensitive to a possible difference between the amount of CP violation as measured on the surface of the Earth and in a lower gravity environment. Our proposed experiment is model independent and could yield a $5\sigma$ measurement within tens of days, indicating a dependence of the level of CP violation in the neutral kaon system on the local gravitational potential., Comment: Contribution to the 2021 Gravitation session of the 55th Rencontres de Moriond

Published
2021

22. Charged particle identification with the liquid xenon calorimeter of the CMD-3 detector

Author

Ivanov, V. L., Fedotovich, G. V., Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Bashtovoy, N. S., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Gayazov, S. E., Grebenuk, A. A., Gribanov, S. S., Grigoriev, D. N., Ignatov, F. V., Karpov, S. V., Kazanin, V. F., Korobov, A. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Mikhailov, K. Yu., Okhapkin, V. S., Pestov, Yu. N., Popov, A. S., Razuvaev, G. P., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Semenov, A. V., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Solodov, E. P., Titov, V. M., Talyshev, A. A., Tolmachev, S. S., Vorobiov, A. I., and Yudin, Yu. V.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The paper describes a method of the charged particle identification, developed for the \mbox{CMD-3} detector, installed at the VEPP-2000 $e^{+}e^{-}$ collider. The method is based on the application of the boosted decision trees classifiers, trained for the optimal separation of electrons, muons, pions and kaons in the momentum range from 100 to $1200~{\rm MeV}/c$. The input variables for the classifiers are linear combinations of the energy depositions of charged particles in 12 layers of the liquid xenon calorimeter of the \mbox{CMD-3}. The event samples for training of the classifiers are taken from the simulation. Various issues of the detector response tuning in simulation and calibration of the calorimeter strip channels are considered. Application of the method is illustrated by the examples of separation of the $e^+e^-(\gamma)$ and $\pi^+\pi^-(\gamma)$ final states and of selection of the $K^+K^-$ final state at high energies.

Published
2020

23. The anomalous magnetic moment of the muon in the Standard Model

Author

Aoyama, T., Asmussen, N., Benayoun, M., Bijnens, J., Blum, T., Bruno, M., Caprini, I., Calame, C. M. Carloni, Cè, M., Colangelo, G., Curciarello, F., Czyż, H., Danilkin, I., Davier, M., Davies, C. T. H., Della Morte, M., Eidelman, S. I., El-Khadra, A. X., Gérardin, A., Giusti, D., Golterman, M., Gottlieb, Steven, Gülpers, V., Hagelstein, F., Hayakawa, M., Herdoíza, G., Hertzog, D. W., Hoecker, A., Hoferichter, M., Hoid, B. -L., Hudspith, R. J., Ignatov, F., Izubuchi, T., Jegerlehner, F., Jin, L., Keshavarzi, A., Kinoshita, T., Kubis, B., Kupich, A., Kupść, A., Laub, L., Lehner, C., Lellouch, L., Logashenko, I., Malaescu, B., Maltman, K., Marinković, M. K., Masjuan, P., Meyer, A. S., Meyer, H. B., Mibe, T., Miura, K., Müller, S. E., Nio, M., Nomura, D., Nyffeler, A., Pascalutsa, V., Passera, M., del Rio, E. Perez, Peris, S., Portelli, A., Procura, M., Redmer, C. F., Roberts, B. L., Sánchez-Puertas, P., Serednyakov, S., Shwartz, B., Simula, S., Stöckinger, D., Stöckinger-Kim, H., Stoffer, P., Teubner, T., Van de Water, R., Vanderhaeghen, M., Venanzoni, G., von Hippel, G., Wittig, H., Zhang, Z., Achasov, M. N., Bashir, A., Cardoso, N., Chakraborty, B., Chao, E. -H., Charles, J., Crivellin, A., Deineka, O., Denig, A., DeTar, C., Dominguez, C. A., Dorokhov, A. E., Druzhinin, V. P., Eichmann, G., Fael, M., Fischer, C. S., Gámiz, E., Gelzer, Z., Green, J. R., Guellati-Khelifa, S., Hatton, D., Hermansson-Truedsson, N., Holz, S., Hörz, B., Knecht, M., Koponen, J., Kronfeld, A. S., Laiho, J., Leupold, S., Mackenzie, P. B., Marciano, W. J., McNeile, C., Mohler, D., Monnard, J., Neil, E. T., Nesterenko, A. V., Ottnad, K., Pauk, V., Radzhabov, A. E., de Rafael, E., Raya, K., Risch, A., Rodríguez-Sánchez, A., Roig, P., José, T. San, Solodov, E. P., Sugar, R., Todyshev, K. Yu., Vainshtein, A., Avilés-Casco, A. Vaquero, Weil, E., Wilhelm, J., Williams, R., and Zhevlakov, A. S.

Subjects
High Energy Physics - Phenomenology, High Energy Physics - Experiment, High Energy Physics - Lattice, Nuclear Experiment, Nuclear Theory
Abstract

We review the present status of the Standard Model calculation of the anomalous magnetic moment of the muon. This is performed in a perturbative expansion in the fine-structure constant $\alpha$ and is broken down into pure QED, electroweak, and hadronic contributions. The pure QED contribution is by far the largest and has been evaluated up to and including $\mathcal{O}(\alpha^5)$ with negligible numerical uncertainty. The electroweak contribution is suppressed by $(m_\mu/M_W)^2$ and only shows up at the level of the seventh significant digit. It has been evaluated up to two loops and is known to better than one percent. Hadronic contributions are the most difficult to calculate and are responsible for almost all of the theoretical uncertainty. The leading hadronic contribution appears at $\mathcal{O}(\alpha^2)$ and is due to hadronic vacuum polarization, whereas at $\mathcal{O}(\alpha^3)$ the hadronic light-by-light scattering contribution appears. Given the low characteristic scale of this observable, these contributions have to be calculated with nonperturbative methods, in particular, dispersion relations and the lattice approach to QCD. The largest part of this review is dedicated to a detailed account of recent efforts to improve the calculation of these two contributions with either a data-driven, dispersive approach, or a first-principle, lattice-QCD approach. The final result reads $a_\mu^\text{SM}=116\,591\,810(43)\times 10^{-11}$ and is smaller than the Brookhaven measurement by 3.7$\sigma$. The experimental uncertainty will soon be reduced by up to a factor four by the new experiment currently running at Fermilab, and also by the future J-PARC experiment. This and the prospects to further reduce the theoretical uncertainty in the near future-which are also discussed here-make this quantity one of the most promising places to look for evidence of new physics., Comment: 196 pages, 103 figures, version published in Phys. Rept., bib files for the citation references are available from: https://muon-gm2-theory.illinois.edu

Published
2020
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24. Search for lepton flavour violating muon decay mediated by a new light particle in the MEG experiment

Author

Baldini, A. M., Berg, F., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiappini, M., Chiarello, G., Chiri, C., Corvaglia, A., de Bari, A., De Gerone, M., Francesconi, M., Galli, L., Gatti, F., Grancagnolo, F., Grassi, M., Grigoriev, D. N., Hildebrandt, M., Hodge, Z., Ieki, K., Ignatov, F., Iwai, R., Iwamoto, T., Kobayashi, S., Kettle, P. -R., Kyle, W., Khomutov, N., Kolesnikov, A., Kravchuk, N., Kuchinskiy, N., Libeiro, T., Lim, G. M. A., Malyshev, V., Matsuzawa, N., Meucci, M., Mihara, S., Molzon, W., Mori, Toshinori, Mtchedilishvili, A., Nakao, M., Natori, H., Nicolò, D., Nishiguchi, H., Nishimura, M., Ogawa, S., Onda, R., Ootani, W., Oya, A., Palo, D., Panareo, M., Papa, A., Pettinacci, V., Pizzigoni, G., Popov, A., Renga, F., Ritt, S., Rozhdestvensky, A., Rossella, M., Sawada, R., Schwendimann, P., Signorelli, G., Stoykov, A., Tassielli, G. F., Toyoda, K., Uchiyama, Y., Usami, M., Voena, C., Yanai, K., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X, $\mu^+ \to \mathrm{e}^+\mathrm{X}, \mathrm{X} \to \gamma\gamma$. This search uses a dataset resulting from $7.5\times 10^{14}$ stopped muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009--2013. No significant excess is found in the mass region 20--45 MeV/c$^2$ for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20--40 MeV/c$^2$, down to $\mathcal{O}(10^{-11})$ at 90\% confidence level.

Published
2020
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25. The anomalous magnetic moment of the muon in the Standard Model

Author

Aoyama, T, Asmussen, N, Benayoun, M, Bijnens, J, Blum, T, Bruno, M, Caprini, I, Calame, CM Carloni, Cè, M, Colangelo, G, Curciarello, F, Czyż, H, Danilkin, I, Davier, M, Davies, CTH, Della Morte, M, Eidelman, SI, El-Khadra, AX, Gérardin, A, Giusti, D, Golterman, M, Gottlieb, Steven, Gülpers, V, Hagelstein, F, Hayakawa, M, Herdoíza, G, Hertzog, DW, Hoecker, A, Hoferichter, M, Hoid, B-L, Hudspith, RJ, Ignatov, F, Izubuchi, T, Jegerlehner, F, Jin, L, Keshavarzi, A, Kinoshita, T, Kubis, B, Kupich, A, Kupść, A, Laub, L, Lehner, C, Lellouch, L, Logashenko, I, Malaescu, B, Maltman, K, Marinković, MK, Masjuan, P, Meyer, AS, Meyer, HB, Mibe, T, Miura, K, Müller, SE, Nio, M, Nomura, D, Nyffeler, A, Pascalutsa, V, Passera, M, del Rio, E Perez, Peris, S, Portelli, A, Procura, M, Redmer, CF, Roberts, BL, Sánchez-Puertas, P, Serednyakov, S, Shwartz, B, Simula, S, Stöckinger, D, Stöckinger-Kim, H, Stoffer, P, Teubner, T, Van de Water, R, Vanderhaeghen, M, Venanzoni, G, von Hippel, G, Wittig, H, Zhang, Z, Achasov, MN, Bashir, A, Cardoso, N, Chakraborty, B, Chao, E-H, Charles, J, Crivellin, A, Deineka, O, Denig, A, DeTar, C, Dominguez, CA, Dorokhov, AE, Druzhinin, VP, Eichmann, G, Fael, M, Fischer, CS, Gámiz, E, Gelzer, Z, Green, JR, Guellati-Khelifa, S, Hatton, D, and Hermansson-Truedsson, N

Subjects
hep-ph, hep-ex, hep-lat, nucl-ex, nucl-th, Mathematical Sciences, Physical Sciences, Nuclear & Particles Physics
Abstract

We review the present status of the Standard Model calculation of the anomalous magnetic moment of the muon. This is performed in a perturbative expansion in the fine-structure constant α and is broken down into pure QED, electroweak, and hadronic contributions. The pure QED contribution is by far the largest and has been evaluated up to and including O(α5) with negligible numerical uncertainty. The electroweak contribution is suppressed by (mμ∕MW)2 and only shows up at the level of the seventh significant digit. It has been evaluated up to two loops and is known to better than one percent. Hadronic contributions are the most difficult to calculate and are responsible for almost all of the theoretical uncertainty. The leading hadronic contribution appears at O(α2) and is due to hadronic vacuum polarization, whereas at O(α3) the hadronic light-by-light scattering contribution appears. Given the low characteristic scale of this observable, these contributions have to be calculated with nonperturbative methods, in particular, dispersion relations and the lattice approach to QCD. The largest part of this review is dedicated to a detailed account of recent efforts to improve the calculation of these two contributions with either a data-driven, dispersive approach, or a first-principle, lattice-QCD approach. The final result reads aμSM=116591810(43)×10−11 and is smaller than the Brookhaven measurement by 3.7σ. The experimental uncertainty will soon be reduced by up to a factor four by the new experiment currently running at Fermilab, and also by the future J-PARC experiment. This and the prospects to further reduce the theoretical uncertainty in the near future – which are also discussed here – make this quantity one of the most promising places to look for evidence of new physics.

Published
2020

26. Measurement of the $e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$ cross section with the CMD-3 detector at the VEPP-2000 collider

Author

Gribanov, S. S., Popov, A. S., Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Banzarov, V. Sh., Bashtovoy, N. S., Berkaev, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Fedotovich, G. V., Gayazov, S. E., Grancagnolo, F. J., Grebenuk, A. A., Grigoriev, D. N., Ignatov, F. V., Ivanov, V. L., Karpov, S. V., Kazanin, V. F., Kirpotin, A. N., Koop, I. A., Korobov, A. A., Kovalenko, O. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Mikhailov, K. Yu., Okhapkin, V. S., Otboev, A. V., Pestov, Yu. N., Razuvaev, G. P., Rogovsky, Yu. A., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Semenov, A. V., Senchenko, A. I., Shatunov, Yu. M., Shatunov, P. Yu., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Solodov, E. P., Titov, V. M., Talyshev, A. A., Tolmachev, S. S., Vorobiov, A. I., Zemlyansky, I. M., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

The cross section of the process $e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$ is measured using the data collected with the CMD-$3$ detector at the VEPP-$2000$ collider in the center-of-mass energy range from $1.1$ to $2.0$ GeV. The decay mode $\eta\rightarrow\gamma\gamma$ is used for $\eta$ meson reconstruction in the data sample corresponding to an integrated luminosity of $78.3$ pb$^{-1}$. The energy dependence of the $e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$ cross section is fitted within the framework of vector meson dominance in order to extract the $\Gamma(\rho(1450)\rightarrow{^{+}e^{-}})\mathcal{B}(\rho(1450)\rightarrow\eta\pi^{+}\pi^{-})$ and the $\Gamma(\rho(1700)\rightarrow{e^{+}e^{-}})\mathcal{B}(\rho(1700)\rightarrow\eta\pi^{+}\pi^{-})$ products. Based on conservation of vector current, the analysed data are used to test the relationship between the $e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$ cross section and the spectral function in $\tau^-\rightarrow\eta\pi^-\pi^0\nu_\tau$ decay. The $e^{+}e^{-}\rightarrow\eta\pi^{+}\pi^{-}$ cross section measured with the CMD-$3$ detector is in good agreement with the previous measurements.

Published
2019
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27. Study of the process $e^+e^-{\to}K^+K^-\eta$ with the CMD-3 detector at the VEPP-2000 collider

Author

Ivanov, V. L., Fedotovich, G. V., Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Banzarov, V. Sh., Bashtovoy, N. S., Berkaev, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Gayazov, S. E., Grebenuk, A. A., Gribanov, S. S., Grigoriev, D. N., Ignatov, F. V., Karpov, S. V., Kasaev, A. S., Kazanin, V. F., Koop, I. A., Korobov, A. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Lysenko, A. P., Mikhailov, K. Yu., Okhapkin, V. S., Perevedentsev, E. A., Pestov, Yu. N., Popov, A. S., Razuvaev, G. P., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Semenov, A. V., Shatunov, Yu. M., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Solodov, E. P., Timoshenko, M. V., Titov, V. M., Talyshev, A. A., Tolmachev, S. S., Vorobiov, A. I., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

The process $e^+e^-{\to}K^+K^-\eta$ has been studied in the center-of-mass energy range from 1.59 to 2.007\,GeV using the data sample of 59.5 pb$^{-1}$, collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider in 2011, 2012 and 2017. The $K^+K^-\eta$ final state is found to be dominated by the contribution of the $\phi(1020)\eta$ intermediate state. The cross section of the process $e^+e^-{\to}\phi(1020)\eta$ has been measured with a systematic uncertainty of 5.1$\%$ on the base of 3009 $\pm$ 67 selected events. The obtained cross section has been used to calculate the contribution to the anomalous magnetic moment of the muon: $a_{\mu}^{\phi\eta}(E<1.8\, {\rm GeV})=(0.321 \pm 0.015_{\rm stat} \pm 0.016_{\rm syst}) \times 10^{-10}$, $a_{\mu}^{\phi\eta}(E<2.0\, {\rm GeV})=(0.440 \pm 0.015_{\rm stat} \pm 0.022_{\rm syst}) \times 10^{-10}$. From the cross section approximation the $\phi(1680)$ meson parameters have been determined with better statistical precision, than in previous studies.

Published
2019
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28. Results on Multiple Coulomb Scattering from 12 and 20 GeV electrons on Carbon targets

Author

Abbiendi, G., Bernhard, J., Betti, F., Bonanomi, M., Calame, C. M. Carloni, Garattini, M., Gavrikov, Y., Hall, G., Iacoangeli, F., Ignatov, F., Incagli, M., Ivanchenko, V., Ligabue, F., James, T. O., Marconi, U., Matteuzzi, C., Passera, M., Pesaresi, M., Piccinini, F., Pilato, R. N., Pisani, F., Principe, A., Scandale, W., Tenchini, R., and Venanzoni, G.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

Multiple scattering effects of 12 and 20 GeV electrons on 8 and 20 mm thickness carbon targets have been studied with high-resolution silicon microstrip detectors of the UA9 apparatus at the H8 line at CERN. Comparison of the scattering angle between data and GEANT4 simulation shows excellent agreement in the core of the distributions leaving some residual disagreement in the tails., Comment: 14 pages, 16 figures. Updated to match published version

Published
2019
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29. COMET Phase-I Technical Design Report

Author

The COMET Collaboration, Abramishvili, R., Adamov, G., Akhmetshin, R. R., Allin, A., Angélique, J. C., Anishchik, V., Aoki, M., Aznabayev, D., Bagaturia, I., Ban, G., Ban, Y., Bauer, D., Baygarashev, D., Bondar, A. E., Cârloganu, C., Carniol, B., Chau, T. T., Chen, J. K., Chen, S. J., Cheung, Y. E., da Silva, W., Dauncey, P. D., Densham, C., Devidze, G., Dornan, P., Drutskoy, A., Duginov, V., Eguchi, Y., Epshteyn, L. B., Evtoukhovich, P., Fayer, S., Fedotovich, G. V., Finger Jr, M., Finger, M., Fujii, Y., Fukao, Y., Gabriel, J. L., Gay, P., Gillies, E., Grigoriev, D. N., Gritsay, K., Hai, V. H., Hamada, E., Hashim, I. H., Hashimoto, S., Hayashi, O., Hayashi, T., Hiasa, T., Ibrahim, Z. A., Igarashi, Y., Ignatov, F. V., Iio, M., Ishibashi, K., Issadykov, A., Itahashi, T., Jansen, A., Jiang, X. S., Jonsson, P., Kachelhoffer, T., Kalinnikov, V., Kaneva, E., Kapusta, F., Katayama, H., Kawagoe, K., Kawashima, R., Kazak, N., Kazanin, V. F., Kemularia, O., Khvedelidze, A., Koike, M., Kormoll, T., Kozlov, G. A., Kozyrev, A. N., Kravchenko, M., Krikler, B., Kumsiashvili, G., Kuno, Y., Kuriyama, Y., Kurochkin, Y., Kurup, A., Lagrange, B., Lai, J., Lee, M. J., Li, H. B., Litchfield, R. P., Li, W. G., Loan, T., Lomidze, D., Lomidze, I., Loveridge, P., Macharashvili, G., Makida, Y., Mao, Y. J., Markin, O., Matsuda, Y., Melkadze, A., Melnik, A., Mibe, T., Mihara, S., Miyamoto, N., Miyazaki, Y., Idris, F. Mohamad, Azmi, K. A. Mohamed Kamal, Moiseenko, A., Moritsu, M., Mori, Y., Motoishi, T., Nakai, H., Nakai, Y., Nakamoto, T., Nakamura, Y., Nakatsugawa, Y., Nakazawa, Y., Nash, J., Natori, H., Niess, V., Nioradze, M., Nishiguchi, H., Noguchi, K., Numao, T., O'Dell, J., Ogitsu, T., Ohta, S., Oishi, K., Okamoto, K., Okamura, T., Okinaka, K., Omori, C., Ota, T., Pasternak, J., Paulau, A., Picters, D., Ponariadov, V., Quémener, G., Ruban, A. A., Rusinov, V., Sabirov, B., Sakamoto, H., Sarin, P., Sasaki, K., Sato, A., Sato, J., Semertzidis, Y. K., Shigyo, N., Shoukavy, Dz., Slunecka, M., Stöckinger, D., Sugano, M., Tachimoto, T., Takayanagi, T., Tanaka, M., Tang, J., Tao, C. V., Teixeira, A. M., Tevzadze, Y., Thanh, T., Tojo, J., Tolmachev, S. S., Tomasek, M., Tomizawa, M., Toriashvili, T., Trang, H., Trekov, I., Tsamalaidze, Z., Tsverava, N., Uchida, T., Uchida, Y., Ueno, K., Velicheva, E., Volkov, A., Vrba, V., Abdullah, W. A. T. Wan, Warin-Charpentier, P., Wong, M. L., Wong, T. S., Wu, C., Xing, T. Y., Yamaguchi, H., Yamamoto, A., Yamanaka, M., Yamane, T., Yang, Y., Yano, T., Yao, W. C., Yeo, B., Yoshida, H., Yoshida, M., Yoshioka, T., Yuan, Y., Yudin, Yu. V., Zdorovets, M. V., Zhang, J., Zhang, Y., and Zuber, K.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into electrons in the field of an aluminium nucleus ($\mu-e$ conversion, $\mu^- N \to e^- N$); a lepton flavor violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90 % upper limit of branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the \mue conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described., Comment: A minor correction applied in Eq. 3

Published
2018
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30. The Cylindrical Drift Chamber of the MEG II experiment

Author

Chiappini, M., Baldini, A.M., Benmansour, H., Cavoto, G., Cei, F., Chiarello, G., Corvaglia, A., Cuna, F., Maso, G. Dal, Francesconi, M., Galli, L., Grancagnolo, F., Grassi, M., Hildebrandt, M., Ignatov, F., Meucci, M., Miccoli, A., Molzon, W., Nicolò, D., Oya, A., Palo, D., Panareo, M., Papa, A., Raffaelli, F., Renga, F., Schwendimann, P., Signorelli, G., Tassielli, G.F., Uchiyama, Y., Venturini, A., Vitali, B., and Voena, C.

Published
2023
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31. The design of the MEG II experiment

Author

Baldini, A. M., Baracchini, E., Bemporad, C., Berg, F., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiappini, M., Chiarello, G., Chiri, C., Cocciolo, G., Corvaglia, A., de Bari, A., De Gerone, M., D'Onofrio, A., Francesconi, M., Fujii, Y., Galli, L., Gatti, F., Grancagnolo, F., Grassi, M., Grigoriev, D. N., Hildebrandt, M., Hodge, Z., Ieki, K., Ignatov, F., Iwai, R., Iwamoto, T., Kaneko, D., Kasami, K., Kettle, P. -R., Khazin, B. I., Khomutov, N., Korenchenko, A., Kravchuk, N., Libeiro, T., Maki, M., Matsuzawa, N., Mihara, S., Milgie, M., Molzon, W., Mori, Toshinori, Morsani, F., Mtchedilishvili, A., Nakao, M., Nakaura, S., Nicoló, D., Nishiguchi, H., Nishimura, M., Ogawa, S., Ootani, W., Panareo, M., Papa, A., Pepino, A., Piredda, G., Popov, A., Raffaelli, F., Renga, F., Ripiccini, E., Ritt, S., Rossella, M., Rutar, G., Sawada, R., Signorelli, G., Simonetta, M., Tassielli, G. F., Uchiyama, Y., Usami, M., Venturini, M., Voena, C., Yoshida, K., Yudin, Yu. V., and Zhang, Y.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The MEG experiment, designed to search for the mu+->e+ gamma decay at a 10^-13 sensitivity level, completed data taking in 2013. In order to increase the sensitivity reach of the experiment by an order of magnitude to the level of 6 x 10-14 for the branching ratio, a total upgrade, involving substantial changes to the experiment, has been undertaken, known as MEG II. We present both the motivation for the upgrade and a detailed overview of the design of the experiment and of the expected detector performance., Comment: 61 pages and 97 figures

Published
2018
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32. Commissioning and preliminary performance of the MEG II drift chamber

Author

Chiappini, M., Chiarello, G., Baldini, A.M., Benmansour, H., Cavoto, G., Cei, F., Corvaglia, A., Cuna, F., Dal Maso, G., Francesconi, M., Galli, L., Grancagnolo, F., Grassi, M., Hildebrandt, M., Ignatov, F., Meucci, M., Miccoli, A., Molzon, W., Nicolò, D., Oya, A., Palo, D., Panareo, M., Papa, A., Raffaelli, F., Renga, F., Schwendimann, P., Signorelli, G., Tassielli, G.F., Uchiyama, Y., Venturini, A., Vitali, B., and Voena, C.

Published
2022
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33. Study of the process $e^+e^- \to K^+K^-$ in the center-of-mass energy range 1010--1060~MeV with the CMD-3 detector

Author

Kozyrev, E. A., Solodov, E. P., Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Banzarov, V. S., Bashtovoy, N. S., Berkaev, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Fedotovich, G. V., Gayazov, S. E., Grebenuk, A. A., Gribanov, S. S., Grigoriev, D. N., Ignatov, F. V., Ivanov, V. L., Karpov, S. V., Kasaev, A. S., Kazanin, V. F., Korobov, A. A., Koop, I. A., Kozyrev, A. N., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Lysenko, A. P., Mikhailov, K. Yu., Okhapkin, V. S., Perevedentsev, E. A., Pestov, Yu. N., Popov, A. S., Razuvaev, G. P., Rogovsky, Yu. A., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Shatunov, Yu. M., Talyshev, A. A., Vorobiov, A. I., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

The process $e^+e^- \to K^+K^-$ has been studied using $1.7 \times 10^6$ events from a data sample corresponding to an integrated luminosity of 5.7 pb$^{-1}$ collected with the CMD-3 detector in the center-of-mass energy range 1010--1060 MeV. The cross section measured with an about 2\% systematic uncertainty and it is used to calculate the contribution to the anomalous magnetic moment of the muon $a_{\mu}^{K^+K^-} = (19.33 \pm 0.40) \times 10^{-10}$, and to obtain the $\phi(1020)$ meson parameters. We consider the relationship between the $e^+e^- \to K^+K^-$ and $e^+e^- \to K^0_SK^0_L$ cross sections and compare it to the theoretical expectations.

Published
2017
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34. Study of the Process $e^+e^-\to \pi^+\pi^-\pi^+\pi^-$ IN THE C.M. Energy Range 920--1060 MeV with the CMD-3 Detector

Author

Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Banzarov, V. Sh., Bashtovoy, N. S., Berkaev, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Fedotovich, G. V., Gayazov, S. E., Grebenuk, A. A., Gribanov, S. S., Grigoriev, D. N., Ignatov, F. V., Ivanov, V. L., Karpov, S. V., Kasaev, A. S., Kazanin, V. F., Koop, I. A., Kovalenko, O. A., Korobov, A. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lysenko, A. P., Lukin, P. A., Mikhailov, K. Yu., Okhapkin, V. S., Pestov, Yu. N., Perevedentsev, E. A., Popov, A. S., Razuvaev, G. P., Rogovsky, Yu. A., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Shatunov, Yu. M., Solodov, E. P., Titov, V. M., Talyshev, A. A., Vorobiov, A. I., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

A cross section of the process $e^+e^- \to \pipi\pipi$ has been measured using 6798$\pm$93 signal events from a data sample corresponding to an integrated luminosity of 9.8 pb$^{-1}$ collected with the CMD-3 detector in the center-of-mass energy range 920--1060 MeV. The measured cross section exhibits an interference pattern of the $\phi(1020)\to\pipi\pipi$ decay with a non-resonant process $e^+e^- \to \pipi\pipi$, from which we obtain the branching fraction of the doubly suppressed decays (by G-parity and OZI rule): $\BR(\phi\to\pipi\pipi) = (6.5\pm2.7\pm1.6)\times 10^{-6}$., Comment: 16 pages, 6 figures

Published
2016
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35. Mini-Proceedings, 18th meeting of the Working Group on Radiative Corrections and MC Generators for Low Energies

Author

Czyż, H., Eidelman, S., Ignatov, F., Keshavarzi, A., Kupsc, A., Lyubovitskij, V. E., Masjuan, P., Nyffeler, A., Pancheri, G., Tomasi-Gustafsson, E., and Venanzoni, G.

Subjects
High Energy Physics - Phenomenology, High Energy Physics - Experiment, Nuclear Experiment, Nuclear Theory
Abstract

The mini-proceedings of the 18$^{\mathrm{th}}$ Meeting of the "Working Group on Radiative Corrections and MonteCarlo Generators for Low Energies" held in Frascati, 19$^{\mathrm{th}}$ - 20$^{\mathrm{st}}$ May, are presented. These meetings, started in 2006, have as aim to bring together experimentalists and theoreticians working in the fields of meson transition form factors, hadronic contributions to the anomalous magnetic moment of the leptons, and the effective fine structure constant. The development of MonteCarlo generators and Radiative Corrections for precision $e^+e^-$ and $\tau$-lepton physics are also covered, with emphasis on meson production. At this workshop, a documentary entitled {\it Bruno Touschek with AdA in Orsay} commemorating the first observation of electron-positron collisions in a laboratory was also presented. With this edition, the working group reaches 10 years of continuous activities., Comment: 27 pages, 10 contributions. Editors: H. Czyz, P. Masjuan, and G. Venanzoni

Published
2016

36. Muon polarization in the MEG experiment: predictions and measurements

Author

Baldini, A. M., Bao, Y., Baracchini, E., Bemporad, C., Berg, F., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiarello, G., Chiri, C., De Bari, A., De Gerone, M., DÓnofrio, A., Dussoni, S., Fujii, Y., Galli, L., Gatti, F., Grancagnolo, F., Grassi, M., Graziosi, A., Grigoriev, D. N., Haruyama, T., Hildebrandt, M., Hodge, Z., Ieki, K., Ignatov, F., Iwamoto, T., Kaneko, D., Kang, T. I., Kettle, P. R., Khazin, B. I., Khomutov, N., Korenchenko, A., Kravchuk, N., Lim, G. M. A., Mihara, S., Molzon, W., Mori, T., Mtchedlishvili, A., Nakaura, S., Nicolò, D., Nishiguchi, H., Nishimura, M., Ogawa, S., Ootani, W., Panareo, M., Papa, A., Pepino, A., Piredda, G., Pizzigoni, G., Popov, A., Renga, F., Ripiccini, E., Ritt, S., Rossella, M., Rutar, G., Sawada, R., Sergiampietri, F., Signorelli, G., Tassielli, G., Tenchini, F., Uchiyama, Y., Venturini, M., Voena, C., Yamamoto, A., Yoshida, K., You, Z., and Yudin, Y. V.

Subjects
High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract

The MEG experiment makes use of one of the world's most intense low energy muon beams, in order to search for the lepton flavour violating process $\mu^{+} \rightarrow {\rm e}^{+} \gamma$. We determined the residual beam polarization at the thin stopping target, by measuring the asymmetry of the angular distribution of Michel decay positrons as a function of energy. The initial muon beam polarization at the production is predicted to be $P_{\mu} = -1$ by the Standard Model (SM) with massless neutrinos. We estimated our residual muon polarization to be $P_{\mu} = -0.85 \pm 0.03 ~ {\rm (stat)} ~ { }^{+ 0.04}_{-0.05} ~ {\rm (syst)}$ at the stopping target, which is consistent with the SM predictions when the depolarizing effects occurring during the muon production, propagation and moderation in the target are taken into account. The knowledge of beam polarization is of fundamental importance in order to model the background of our ${\megsign}$ search induced by the muon radiative decay: $\mu^{+} \rightarrow {\rm e}^{+} \bar{\nu}_{\mu} \nu_{\rm e} \gamma$.

Published
2015
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37. Measurement of the $e^+e^- \to K^+K^-\pi^+\pi^-$ cross section with the CMD-3 detector at the VEPP-2000 collider

Author

Shemyakin, D. N., Fedotovich, G. V., Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Banzarov, V. Sh., Bashtovoy, N. S., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Gayazov, S. E., Grebenuk, A. A., Gribanov, S. S., Grigoriev, D. N., Ignatov, F. V., Ivanov, V. L., Karpov, S. V., Kazanin, V. F., Koop, I. A., Korobov, A. A., Kovalenko, O. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lysenko, A. P., Lukin, P. A., Mikhailov, K. Yu., Okhapkin, V. S., Pestov, Yu. N., Perevedentsev, E. A., Popov, A. S., Razuvaev, G. P., Rogovsky, Yu. A., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Shebalin, V. E., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Shatunov, Yu. M., Solodov, E. P., Titov, V. M., Talyshev, A. A., Vorobiov, A. I., Yudin, Yu. V., and Zemlyansky, I. M.

Subjects
High Energy Physics - Experiment, Nuclear Experiment
Abstract

The process $e^+e^- \to K^+K^-\pi^+\pi^-$ has been studied in the center-of-mass energy range from 1500 to 2000\,MeV using a data sample of 23 pb$^{-1}$ collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider. Using about 24000 selected events, the $e^+e^- \to K^+K^-\pi^+\pi^-$ cross section has been measured with a systematic uncertainty decreasing from 11.7\% at 1500-1600\,MeV to 6.1\% above 1800\,MeV. A preliminary study of $K^+K^-\pi^+\pi^-$ production dynamics has been performed.

Published
2015
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38. Study of the process $e^+e^-\to p\bar{p}$ in the c.m. energy range from threshold to 2 GeV with the CMD-3 detector

Author

Akhmetshin, R. R., Amirkhanov, A. N., Anisenkov, A. V., Aulchenko, V. M., Banzarov, V. Sh., Bashtovoy, N. S., Berkaev, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Fedotovich, G. V., Gayazov, S. E., Grebenuk, A. A., Gribanov, S. S., Grigoriev, D. N., Gromov, E. M., Ignatov, F. V., Ivanov, V. L., Karpov, S. V., Kasaev, A. S., Kazanin, V. F., Khazin, B. I., Kirpotin, A. N., Koop, I. A., Kovalenko, O. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Mikhailov, K. Yu., Okhapkin, V. S., Otboev, A. V., Pestov, Yu. N., Pivovarov, S. G., Popov, A. S., Razuvaev, G. P., Romanov, A. L., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Shatunov, P. Yu., Shatunov, Yu. M., Solodov, E. P., Titov, V. M., Talyshev, A. A., Vorobiov, A. I., Yudin, Yu. V., and Zharinov, Yu. M.

Subjects
High Energy Physics - Experiment
Abstract

Using a data sample of 6.8 pb$^{-1}$ collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider we select about 2700 events of the $e^+e^- \to p\bar{p}$ process and measure its cross section at 12 energy ponts with about 6\% systematic uncertainty. From the angular distribution of produced nucleons we obtain the ratio $|G_{E}/G_{M}| = 1.49 \pm 0.23 \pm 0.30$.

Published
2015
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39. Mu2e Technical Design Report

Author

Bartoszek, L., Barnes, E., Miller, J. P., Mott, J., Palladino, A., Quirk, J., Roberts, B. L., Crnkovic, J., Polychronakos, V., Tishchenko, V., Yamin, P., Cheng, C. -h., Echenard, B., Flood, K., Hitlin, D. G., Kim, J. H., Miyashita, T. S., Porter, F. C., Röhrken, M., Trevor, J., Zhu, R. -Y., Heckmaier, E., Kang, T. I., Lim, G., Molzon, W., You, Z., Artikov, A. M., Budagov, J. A., Davydov, Yu. I., Glagolev, V. V., Simonenko, A. V., Usubov, Z. U., Oh, S. H., Wang, C., Ambrosio, G., Andreev, N., Arnold, D., Ball, M., Bernstein, R. H., Bianchi, A., Biery, K., Bossert, R., Bowden, M., Brandt, J., Brown, G., Brown, H., Buehler, M., Campbell, M., Cheban, S., Chen, M., Coghill, J., Coleman, R., Crowley, C., Deshpande, A., Deuerling, G., Dey, J., Dhanaraj, N., Dinnon, M., Dixon, S., Drendel, B., Eddy, N., Evans, R., Evbota, D., Fagan, J., Feher, S., Fellenz, B., Friedsam, H., Gallo, G., Gaponenko, A., Gardner, M., Gaugel, S., Genser, K., Ginther, G., Glass, H., Glenzinski, D., Hahn, D., Hansen, S., Hartsell, B., Hays, S., Hocker, J. A., Huedem, E., Huffman, D., Ibrahim, A., Johnstone, C., Kashikhin, V., Kashikhin, V. V., Kasper, P., Kiper, T., Knapp, D., Knoepfel, K., Kokoska, L., Kozlovsky, M., Krafczyk, G., Kramp, M., Krave, S., Krempetz, K., Kutschke, R. K., Kwarciany, R., Lackowski, T., Lamm, M. J., Larwill, M., Leavell, F., Leeb, D., Leveling, A., Lincoln, D., Logashenko, V., Lombardo, V., Lopes, M. L., Makulski, A., Martinez, A., McArthur, D., McConologue, F., Michelotti, L., Mokhov, N., Morgan, J., Mukherjee, A., Murat, P., Nagaslaev, V., Neuffer, D. V., Nicol, T., Niehoff, J., Nogiec, J., Olson, M., Orris, D., Ostojic, R., Page, T., Park, C., Peterson, T., Pilipenko, R., Pla-Dalmau, A., Poloubotko, V., Popovic, M., Prebys, E., Prieto, P., Pronskikh, V., Pushka, D., Rabehl, R., Ray, R. E., Rechenmacher, R., Rivera, R., Robotham, W., Rubinov, P., Rusu, V. L., Scarpine, V., Schappert, W., Schoo, D., Stefanik, A., Still, D., Tang, Z., Tanovic, N., Tartaglia, M., Tassotto, G., Tinsley, D., Tschirhart, R. S., Vogel, G., Wagner, R., Wands, R., Wang, M., Werkema, S., White Jr., H. B., Whitmore, J., Wielgos, R., Woods, R., Worel, C., Zifko, R., Ciambrone, P., Colao, F., Cordelli, M., Corradi, G., Dane, E., Giovannella, S., Happacher, F., Luca, A., Miscetti, S., Ponzio, B., Pileggi, G., Saputi, A., Sarra, I., Soleti, R. S., Stomaci, V., Martini, M., Fabbricatore, P., Farinon, S., Musenich, R., Alexander, D., Daniel, A., Empl, A., Hungerford, E. V., Lau, K., Gollin, G. D., Huang, C., Roderick, D., Trundy, B., Brown, D. Na., Ding, D., Kolomensky, Yu. G., Lee, M. J., Cascella, M., Grancagnolo, F., Ignatov, F., Innocente, A., L'Erario, A., Miccoli, A., Maffezzoli, A., Mazzotta, P., Onorato, G., Piacentino, G. M., Rella, S., Rossetti, F., Spedicato, M., Tassielli, G., Taurino, A., Zavarise, G., Hooper, R., Brown, D. No., Djilkibaev, R., Matushko, V., Ankenbrandt, C., Boi, S., Dychkant, A., Hedin, D., Hodge, Z., Khalatian, V., Majewski, R., Martin, L., Okafor, U., Pohlman, N., Riddel, R. S., Shellito, A., de Gouvea, A. L., Cervelli, F., Carosi, R., Di Falco, S., Donati, S., Lomtadze, T., Pezzullo, G., Ristori, L., Spinella, F., Jones, M., Corcoran, M. D., Orduna, J., Rivera, D., Bennett, R., Caretta, O., Davenne, T., Densham, C., Loveridge, P., Odell, J., Bomgardner, R., Dukes, E. C., Ehrlich, R., Frank, M., Goadhouse, S., Group, R., Ho, E., Ma, H., Oksuzian, Y., Purvis, J., Wu, Y., Hertzog, D. W., Kammel, P., Lynch, K. R., and Popp, J. L.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The Mu2e experiment at Fermilab will search for charged lepton flavor violation via the coherent conversion process mu- N --> e- N with a sensitivity approximately four orders of magnitude better than the current world's best limits for this process. The experiment's sensitivity offers discovery potential over a wide array of new physics models and probes mass scales well beyond the reach of the LHC. We describe herein the preliminary design of the proposed Mu2e experiment. This document was created in partial fulfillment of the requirements necessary to obtain DOE CD-2 approval., Comment: compressed file, 888 pages, 621 figures, 126 tables; full resolution available at http://mu2e.fnal.gov; corrected typo in background summary, Table 3.4

Published
2015

40. Search for the process $e^+e^-\to \eta^\prime(958)$ with the CMD-3 detector

Author

Akhmetshin, R. R., Anisenkov, A. V., Aulchenko, V. M., Banzarov, V. Sh., Bashtovoy, N. S., Berkaeva, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Erofeev, A. L., Fedotovich, G. V., Gayazov, S. E., Grebenuk, A. A., Grigoriev, D. N., Gromov, E. N., Ignatov, F. V., Karpov, S. V., Kazanin, V. F., Khazin, B. I., Koop, I. A., Kovalenko, O. A., Kozyrev, A. N., Kozyrev, E. A., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Mikhailov, K. Yu., Muchnoi, N. Yu., Okhapkin, V. S., Pestov, Yu. N., Perevedentsev, E. A., Popov, A. S., Razuvaev, G. P., Rogovsky, Yu. A., Romanov, A. L., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Shatunov, P. Yu., Shatunov, Yu. M., Solodov, E. P., Titova, V. M., Talyshev, A. A., Vorobiov, A. I., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

A search for the process $\epem\to \eta^\prime(958)$ in the $\pipi\eta\to\pipi\gamma\gamma$ final state has been performed with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider. Using an integrated luminosity of 2.69 pb$^{-1}$ collected at the center-of-mass energy \Ecm = 957.68 MeV we set an upper limit for the product of electronic width and branching fractions $\Gamma_{\eta^\prime(958)\to\epem}\cdot\BR_{\eta^\prime(958)\to\pipi\eta}\cdot\BR_{\eta\to\gamma\gamma}<0.00041$ eV at 90\% C.L., Comment: 12 pages, 5 figures, submitted to Physics Letters B

Published
2014
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41. Measurement of the radiative decay of polarized muons in the MEG experiment

Author

MEG Collaboration, Baldini, A. M., Bao, Y., Baracchini, E., Bemporad, C., Berg, F., Biasotti, M., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Chiarello, G., Chiri, C., de Bari, A., De Gerone, M., D'Onofrio, A., Dussoni, S., Fujii, Y., Galli, L., Gatti, F., Grancagnolo, F., Grassi, M., Graziosi, A., Grigoriev, D. N., Haruyama, T., Hildebrandt, M., Hodge, Z., Ieki, K., Ignatov, F., Iwamoto, T., Kaneko, D., Kang, Tae Im, Kettle, P. -R., Khazin, B. I., Khomutov, N., Korenchenko, A., Kravchuk, N., Lim, G. M. A., Mihara, S., Molzon, W., Mori, Toshinori, Mtchedlishvili, A., Nakaura, S., Nicolò, D., Nishiguchi, H., Nishimura, M., Ogawa, S., Ootani, W., Panareo, M., Papa, A., Pepino, A., Piredda, G., Pizzigoni, G., Popov, A., Renga, F., Ripiccini, E., Ritt, S., Rossella, M., Rutar, G., Sawada, R., Sergiampietri, F., Signorelli, G., Tassielli, G. F., Tenchini, F., Uchiyama, Y., Venturini, M., Voena, C., Yamamoto, A., Yoshida, K., You, Z., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment, High Energy Physics - Phenomenology, Physics - Instrumentation and Detectors
Abstract

We studied the radiative muon decay $\mu^+ \to e^+\nu\bar{\nu}\gamma$ by using for the first time an almost fully polarized muon source. We identified a large sample (~13000) of these decays in a total sample of 1.8x10^14 positive muon decays collected in the MEG experiment in the years 2009--2010 and measured the branching ratio B($\mu^+ \to e^+\nu\bar{\nu}\gamma$) = (6.03+-0.14(stat.)+-0.53(sys.))x10^-8 for E_e > 45 MeV and E_{\gamma} > 40 MeV, consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for $\mu^+ \to e^+\gamma$ process., Comment: 8 pages, 7 figures. Added an introduction to NLO calculation which was recently calculated. Published version

Published
2013
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42. The MEG detector for ${\mu}+\to e+{\gamma}$ decay search

Author

Adam, J., Bai, X., Baldini, A. M., Baracchini, E., Bemporad, C., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Cerri, C., Corbo, M., Curalli, N., De Bari, A., De Gerone, M., Del Frate, L., Doke, S., Dussoni, S., Egger, J., Fratini, K., Fujii, Y., Galli, L., Galeotti, S., Gallucci, G., Gatti, F., Golden, B., Grassi, M., Graziosi, A., Grigoriev, D. N., Haruyama, T., Hisamatsu, M. Hildebrandt Y., Ignatov, F., Iwamoto, T., Kaneko, D., Kasami, K., Kettle, P. -R., Khazin, B. I., Korenchenko, O. Kiselev A., Kravchuk, N., Lim, G., Maki, A., Mihara, S., Molzon, W., Mori, T., Morsani, F., Mzavia, D., Nardò, R., Natori, H., Nicolò, D., Nishiguchi, H., Ootani, Y. Nishimura W., Ozone, K., Panareo, M., Papa, A., Pazzi, R., Piredda, G., Popov, A., Raffaelli, F., Renga, F., Ripiccini, E., Ritt, S., Rossella, M., Sawada, R., Schneebeli, M., Sergiampietri, F., Signorelli, G., Suzuki, S., Tenchini, F., Topchyan, C., Uchiyama, Y., Voena, R. Valle C., Xiao, F., Yamada, S., Yamamoto, S., Yamashita, S., Yudin, Yu. V., and Zanello, D.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment
Abstract

The MEG (Mu to Electron Gamma) experiment has been running at the Paul Scherrer Institut (PSI), Switzerland since 2008 to search for the decay \meg\ by using one of the most intense continuous $\mu^+$ beams in the world. This paper presents the MEG components: the positron spectrometer, including a thin target, a superconducting magnet, a set of drift chambers for measuring the muon decay vertex and the positron momentum, a timing counter for measuring the positron time, and a liquid xenon detector for measuring the photon energy, position and time. The trigger system, the read-out electronics and the data acquisition system are also presented in detail. The paper is completed with a description of the equipment and techniques developed for the calibration in time and energy and the simulation of the whole apparatus., Comment: 59 pages, 90 figures

Published
2013
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43. New constraint on the existence of the mu+-> e+ gamma decay

Author

MEG Collaboration, Adam, J., Bai, X., Baldini, A. M., Baracchini, E., Bemporad, C., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Cerri, C., de Bari, A., De Gerone, M., Doke, T., Dussoni, S., Egger, J., Fratini, K., Fujii, Y., Galli, L., Gallucci, G., Gatti, F., Golden, B., Grassi, M., Graziosi, A., Grigoriev, D. N., Haruyama, T., Hildebrandt, M., Hisamatsu, Y., Ignatov, F., Iwamoto, T., Kaneko, D., Kettle, P. -R., Khazin, B. I., Khomotov, N., Kiselev, O., Korenchenko, A., Kravchuk, N., Lim, G., Maki, A., Mihara, S., Molzon, W., Mori, T., Mzavia, D., Nardo, R., Natori, H., Nicolo, D., Nishiguchi, H., Nishimura, Y., Ootani, W., Panareo, M., Papa, A., Pazzi, R., Piredda, G., Popov, A., Renga, F., Ripiccini, E., Ritt, S., Rossella, M., Sawada, R., Sergiampietri, F., Signorelli, G., Suzuki, S., Tenchini, F., Topchyan, C., Uchiyama, Y., Valle, R., Voena, C., Xiao, F., Yamada, S., Yamamoto, A., Yamashita, S., You, Z., Yudin, Yu. V., and Zanello, D.

Subjects
High Energy Physics - Experiment, Physics - Instrumentation and Detectors
Abstract

The analysis of a combined data set, totaling 3.6 \times 10^14 stopped muons on target, in the search for the lepton flavour violating decay mu^+ -> e^+ gamma is presented. The data collected by the MEG experiment at the Paul Scherrer Institut show no excess of events compared to background expectations and yield a new upper limit on the branching ratio of this decay of 5.7 \times 10^-13 (90% confidence level). This represents a four times more stringent limit than the previous world best limit set by MEG., Comment: 5 pages, 3 figures, a version accepted in Phys. Rev. Lett

Published
2013

44. Study of the process $e^+e^-\to 3(\pi^+\pi^-)$ in the c.m.energy range 1.5--2.0 gev with the cmd-3 detector

Author

Collaboration, CMD-3, Akhmetshin, R. R., Anisenkov, A. V., Anokhin, S. A., Aulchenko, V. M., Banzarov, V. S., Barkov, L. M., Bashtovoy, N. S., Berkaev, D. E., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Epshteyn, L. B., Fedotovich, G. V., Gayazov, S. E., Grebenuk, A. A., Grigoriev, D. N., Gromov, E. N., Ignatov, F. V., Karpov, S. V., Kazanin, V. F., Khazin, B. I., Koop, I. A., Kozyrev, A. N., Krokovny, P. P., Kuzmenko, A. E., Kuzmin, A. S., Logashenko, I. B., Lysenko, A. P., Lukin, P. A., Mikhailov, K. Yu., Pestov, Yu. N., Perevedentsev, E. A., Pirogov, S. A., Pivovarov, S. G., Popov, A. S., Popov, Yu. S., Redin, S. I., Rogovsky, Yu. A., Romanov, A. L., Ruban, A. A., Ryskulov, N. M., Ryzhenenkov, A. E., Shebalin, V. E., Shemyakin, D. N., Shwartz, B. A., Shwartz, D. B., Sibidanov, A. L., Shatunov, P. Yu., Shatunov, Yu. M., Snopkov, I. G., Solodov, E. P., Titov, V. M., Talyshev, A. A., Vorobiov, A. I., Yudin, Yu. V., and Zaytsev, A. S.

Subjects
High Energy Physics - Experiment
Abstract

The cross section of the process $e^+e^- \to 3(\pi^+\pi^-)$ has been measured using 22 pb$^{-1}$ of integrated luminosity collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider in the c.m. energy range 1.5 -- 2.0 GeV. The measured cross section exhibits a sharp drop near the $p\bar p$ threshold. A first study of dynamics of six-pion production has been performed.

Published
2013

45. MEG Upgrade Proposal

Author

Baldini, A. M., Cei, F., Cerri, C., Dussoni, S., Galli, L., Grassi, M., Nicolò, D., Raffaelli, F., Sergiampietri, F., Signorelli, G., Tenchini, F., Bagliani, D., De Gerone, M., Gatti, F., Baracchini, E., Fujii, Y., Iwamoto, T., Kaneko, D., Mori, T., Nishimura, M., Ootani, W., Sawada, R., Uchiyama, Y., Boca, G., Cattaneo, P. W., de Bari, A., Nardò, R., Rossella, M., Cascella, M., Grancagnolo, F., L'Erario, A., Maffezzoli, A., Miccoli, A., Onorato, G., Palamà, G., Panareo, M., Pepino, A., Rella, S., Tassielli, G. F., Zavarise, G., Cavoto, G., Graziosi, A., Piredda, G., Ripiccini, E., Voena, C., Grigoriev, D. N., Ignatov, F., Khazin, B. I., Popov, A., Yudin, Yu. V., Haruyama, T., Mihara, S., Nishiguchi, H., Yamamoto, A., Hildebrandt, M., Kettle, P. -R., Papa, A., Renga, F., Ritt, S., Stoykov, A., Kang, T. I., Lim, G., Molzon, W., You, Z., Khomutov, N., Korenchenko, A., Kravchuk, N., and Kuchinksy, N.

Subjects
Physics - Instrumentation and Detectors, High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract

We propose the continuation of the MEG experiment to search for the charged lepton flavour violating decay (cLFV) \mu \to e \gamma, based on an upgrade of the experiment, which aims for a sensitivity enhancement of one order of magnitude compared to the final MEG result, down to the $6 \times 10^{-14}$ level. The key features of this new MEG upgrade are an increased rate capability of all detectors to enable running at the intensity frontier and improved energy, angular and timing resolutions, for both the positron and photon arms of the detector. On the positron-side a new low-mass, single volume, high granularity tracker is envisaged, in combination with a new highly segmented, fast timing counter array, to track positron from a thinner stopping target. The photon-arm, with the largest liquid xenon (LXe) detector in the world, totalling 900 l, will also be improved by increasing the granularity at the incident face, by replacing the current photomultiplier tubes (PMTs) with a larger number of smaller photosensors and optimizing the photosensor layout also on the lateral faces. A new DAQ scheme involving the implementation of a new combined readout board capable of integrating the diverse functions of digitization, trigger capability and splitter functionality into one condensed unit, is also under development. We describe here the status of the MEG experiment, the scientific merits of the upgrade and the experimental methods we plan to use., Comment: A. M. Baldini and T. Mori Spokespersons. Research proposal submitted to the Paul Scherrer Institute Research Committee for Particle Physics at the Ring Cyclotron. 131 Pages

Published
2013

46. New limit on the lepton-flavour violating decay mu -> e gamma

Author

MEG collaboration, Adam, J., Bai, X., Baldini, A. M., Baracchini, E., Bemporad, C., Boca, G., Cattaneo, P. W., Cavoto, G., Cei, F., Cerri, C., de Bari, A., De Gerone, M., Doke, T., Dussoni, S., Egger, J., Fratini, K., Fujii, Y., Galli, L., Gallucci, G., Gatti, F., Golden, B., Grassi, M., Grigoriev, D. N., Haruyama, T., Hildebrandt, M., Hisamatsu, Y., Ignatov, F., Iwamoto, T., Kettle, P. -R., Khazin, B. I., Kiselev, O., Korenchenko, A., Kravchuk, N., Maki, A., Mihara, S., Molzon, W., Mori, T., Mzavia, D., Natori, H., Nicolò, D., Nishiguchi, H., Nishimura, Y., Ootani, W., Panareo, M., Papa, A., Pazzi, R., Piredda, G., Popov, A., Renga, F., Ritt, S., Rossella, M., Sawada, R., Sergiampietri, F., Signorelli, G., Suzuki, S., Tenchini, F., Topchyan, C., Uchiyama, Y., Valle, R., Voena, C., Xiao, F., Yamada, S., Yamamoto, A., Yamashita, S., Yudin, Yu. V., and Zanello, D.

Subjects
High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract

We present a new result based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institut in 2009 and 2010, in search of the lepton flavour violating decay mu->e gamma. The likelihood analysis of the combined data sample, which corresponds to a total of 1.8 x 10**14 muon decays, gives a 90% C.L. upper limit of 2.4 x 10**-12 on the branching ratio of the mu->e gamma decay, constituting the most stringent limit on the existence of this decay to date., Comment: 5 pages, 2 figures, accepted for publication at Phys. Rev. Lett

Published
2011
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47. Measurement of $\phi$(1020) meson leptonic width with CMD-2 detector at VEPP-2M Collider

Author

Akhmetshin, R. R., Aulchenko, V. M., Banzarov, V. Sh., Barkov, L. M., Baru, S. E., Bashtovoy, N. S., Bondar, A. E., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Fedotovich, G. V., Gabyshev, N. I., Grebenuk, A. A., Grigoriev, D. N., Ignatov, F. V., Karpov, S. V., Kazanin, V. F., Khazin, B. I., Koop, I. A., Krokovny, P. P., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Lysenko, A. P., Mikhailov, K. Yu., Okhapkin, V. S., Perevedentsev, E. A., Popov, A. S., Redin, S. I., Ruban, A. A., Ryskulov, N. M., Shatunov, Yu. M., Shwartz, B. A., Sibidanov, A. L., Snopkov, I. G., Solodov, E. P., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

The $\phi$(1020) meson leptonic width has been determined from the combined analysis of 4 major decay modes of the resonance ($\phi\to K^+ K^-,K^0_LK^0_S,\pi^+\pi^-\pi^0,\eta\gamma$) studied with the CMD-2 detector at the VEPP-2M $e^+e^-$ collider. The following value has been obtained: $\Gamma(\phi\to e^+e^-) = 1.235\pm 0.006\pm 0.022$ keV. The $\phi(1020)$ meson parameters in four main decay channels have been also recalculated: $B(\phi\to K^+K^-) = 0.493\pm 0.003\pm 0.007$, $B(\phi\to K_LK_S) = 0.336\pm 0.002\pm 0.006$, $B(\phi\to\pi^+\pi^-\pi^0) = 0.155\pm 0.002\pm 0.005$, $B(\phi\to\eta\gamma) = 0.0138\pm 0.0002\pm 0.0002$., Comment: 14 pages, 3 figures

Published
2010
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48. Quest for precision in hadronic cross sections at low energy: Monte Carlo tools vs. experimental data

Author

Actis, S., Arbuzov, A., Balossini, G., Beltrame, P., Bignamini, C., Bonciani, R., Calame, C. M. Carloni, Cherepanov, V., Czakon, M., Czyz, H., Denig, A., Eidelman, S., Fedotovich, G. V., Ferroglia, A., Gluza, J., Grzelinska, A., Gunia, M., Hafner, A., Ignatov, F., Jadach, S., Jegerlehner, F., Kalinowski, A., Kluge, W., Korchin, A., Kuhn, J. H., Kuraev, E. A., Lukin, P., Mastrolia, P., Montagna, G., Muller, S. E., Nguyen, F., Nicrosini, O., Nomura, D., Pakhlova, G., Pancheri, G., Passera, M., Penin, A., Piccinini, F., Placzek, W., Przedzinski, T., Remiddi, E., Riemann, T., Rodrigo, G., Roig, P., Shekhovtsova, O., Shen, C. P., Sibidanov, A. L., Teubner, T., Trentadue, L., Venanzoni, G., van der Bij, J. J., Wang, P., Ward, B. F. L., Was, Z., Worek, M., and Yuan, C. Z.

Subjects
High Energy Physics - Phenomenology, High Energy Physics - Experiment
Abstract

We present the achievements of the last years of the experimental and theoretical groups working on hadronic cross section measurements at the low energy e+e- colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on tau decays. We sketch the prospects in these fields for the years to come. We emphasise the status and the precision of the Monte Carlo generators used to analyse the hadronic cross section measurements obtained as well with energy scans as with radiative return, to determine luminosities and tau decays. The radiative corrections fully or approximately implemented in the various codes and the contribution of the vacuum polarisation are discussed., Comment: Report of the "Working Group on Radiative Corrections and Monte Carlo Generators for Low Energies"; 99 pages, submitted to EPJC

Published
2009
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49. A limit for the mu -> e gamma decay from the MEG experiment

Author

MEG collaboration, Adam, J., Bai, X., Baldini, A., Baracchini, E., Barchiesi, A., Bemporad, C., Boca, G., Cattaneo, P. W., Cavoto, G., Cecchet, G., Cei, F., Cerri, C., De Bari, A., De Gerone, M., Doke, T., Dussoni, S., Egger, J., Galli, L., Gallucci, G., Gatti, F., Golden, B., Grassi, M., Grigoriev, D. N., Haruyama, T., Hildebrandt, M., Hisamatsu, Y., Ignatov, F., Iwamoto, T., Kaneko, D., Kettle, P. -R., Khazin, B. I., Kiselev, O., Korenchenko, A., Kravchuk, N., Maki, A., Mihara, S., Molzon, W., Mori, T., Mzavia, D., Natori, H., Nardò, R., Nicolò, D., Nishiguchi, H., Nishimura, Y., Ootani, W., Panareo, M., Papa, A., Pazzi, R., Piredda, G., Popov, A., Renga, F., Ritt, S., Rossella, M., Sawada, R., Schneebeli, M., Sergiampietri, F., Signorelli, G., Suzuki, S., Topchyan, C., Tumakov, V., Uchiyama, Y., Valle, R., Voena, C., Xiao, F., Yamada, S., Yamamoto, A., Yamashita, S., Yudin, Yu. V., and Zanello, D.

Subjects
High Energy Physics - Experiment, High Energy Physics - Phenomenology
Abstract

A search for the decay mu -> e gamma, performed at PSI and based on data from the initial three months of operation of the MEG experiment, yields an upper limit on the branching ratio of BR(mu -> e gamma) < 2.8 x 10**-11 (90% C.L.). This corresponds to the measurement of positrons and photons from ~ 10**14 stopped mu-decays by means of a superconducting positron spectrometer and a 900 litre liquid xenon photon detector., Comment: 13 pages, 9 figures. v2: improved estimate of photon reconstruction efficiency

Published
2009
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50. Measurement of e+e- -> phi -> K+K- cross section with the CMD-2 detector at VEPP-2M Collider

Author

Collaboration, CMD-2, Akhmetshin, R. R., Aulchenko, V. M., Banzarov, V. Sh., Barkov, L. M., Baru, S. E., Bashtovoy, N. S., Bondar, A. E., Bondarev, D. V., Bragin, A. V., Eidelman, S. I., Epifanov, D. A., Fedotovich, G. V., Gabyshev, N. I., Grebeniuk, A. A., Grigoriev, D. N., Ignatov, F. V., Karpov, S. V., Kazanin, V. F., Khazin, B. I., Koop, I. A., Krokovny, P. P., Kuzmin, A. S., Logashenko, I. B., Lukin, P. A., Lysenko, A. P., Mikhailov, K. Yu., Okhapkin, V. S., Perevedentsev, E. A., Popov, A. S., Redin, S. I., Ruban, A. A., Ryskulov, N. M., Shatunov, Yu. M., Shwartz, B. A., Sibidanov, A. L., Snopkov, I. G., Solodov, E. P., and Yudin, Yu. V.

Subjects
High Energy Physics - Experiment
Abstract

The process e+ e- -> phi -> K+ K- has been studied with the CMD-2 detector using about 542 000 events detected in the center-of-mass energy range from 1.01 to 1.034 GeV. The systematic error of the cross section is estimated to be 2.2%. The phi(1020) meson parameters in the phi -> K+K- decay channel have been measured: sigma_0(phi-> K+K-) = 2016 +- 8 +- 44 nb, m(phi) = 1019.441 +- 0.008 +- 0.080 MeV/c2, Gamma(phi) = 4.24 +- 0.02 +- 0.03 MeV, B(e+e-)B(K+K-) = (14.27 +- 0.05 +- 0.31)*10(-5)., Comment: 12 pages, 6 figures, 2 tables, uses elsart.cls (second version - some figures are corrected)

Published
2008
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