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14 results on '"Lugert, S."'

1. Data on Is and Ic in γ→p→pπ0π0 reveal cascade decays of N(1900) via N(1520)π

Author

Sokhoyan, V., Gutz, E., van Pee, H., Anisovich, A.V., Bacelar, J.C.S., Bantes, B., Bartholomy, O., Bayadilov, D., Beck, R., Beloglazov, Y., Castelijns, R., Crede, V., Dutz, H., Elsner, D., Ewald, R., Frommberger, F., Fuchs, M., Funke, Ch., Gregor, R., Gridnev, A., Hillert, W., Hoffmeister, Ph., Horn, I., Jaegle, I., Junkersfeld, J., Kalinowsky, H., Kammer, S., Kleber, V., Klein, Frank, Klein, Friedrich, Klempt, E., Kotulla, M., Krusche, B., Lang, M., Löhner, H., Lopatin, I., Lugert, S., Mertens, T., Messchendorp, J.G., Metag, V., Nanova, M., Nikonov, V.A., Novinski, D., Novotny, R., Ostrick, M., Pant, L., Pfeiffer, M., Piontek, D., Roy, A., Sarantsev, A.V., Schmidt, Ch., Schmieden, H., Shende, S., Süle, A., Sumachev, V.V., Szczepanek, T., Thiel, A., Thoma, U., Trnka, D., Varma, R., Walther, D., Wendel, Ch., and Wilson, A.

Subjects
Nuclear and High Energy Physics
Published
2015
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2. Photoproduction of �� Mesons off the Proton

Author

Wilson, A., Crede, V., Anisovich, A. V., Bacelar, J. C. S., Bantes, B., Bartholomy, O., Bayadilov, D., Beck, R., Beloglazov, Y. A., Brinkmann, K. T., Castelijns, R., Dutz, H., Elsner, D., Ewald, R., Frommberger, F., Fuchs, M., Funke, Chr., Gregor, R., Gridnev, A., Gutz, E., Hannappel, J., Hillert, W., Hoffmeister, P., Horn, I., Jaegle, I., Jude, T., Junkersfeld, J., Kalinowsky, H., Kleber, V., Klein, Frank, Klein, Friedrich, Klempt, E., Kotulla, M., Krusche, B., Lang, M., L��hner, H., Lopatin, I. V., Lugert, S., Mertens, T., Messchendorp, J. G., Metag, V., Nanova, M., Nikonov, V. A., Novinski, D., Novotny, R., Ostrick, M., Pant, L. M., van Pee, H., Pfeiffer, M., Roy, A., Sarantsev, A. V., Schmidt, C., Schmieden, H., Shende, S., Sokhoyan, V., Sparks, N., S��le, A., Sumachev, V. V., Szczepanek, T., Thoma, U., Trnka, D., Varma, R., Walther, D., Wendel, Ch., and Wiedner, U.

Subjects
High Energy Physics - Experiment (hep-ex), FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

The differential cross sections and unpolarized spin-density matrix elements for the reaction $��p\to p��$ were measured using the CBELSA/TAPS experiment for initial photon energies ranging from the reaction threshold to 2.5 GeV. These observables were measured from the radiative decay of the $��$ meson, $��\to��^0��$. The cross sections cover the full angular range and show the full extent of the $t$-channel forward rise. The overall shape of the angular distributions in the differential cross sections and unpolarized spin-density matrix elements are in fair agreement with previous data. In addition, for the first time, a beam of linearly-polarized tagged photons in the energy range from 1150 MeV to 1650 MeV was used to extract polarized spin-density matrix elements. These data were included in the Bonn-Gatchina partial wave analysis (PWA). The dominant contribution to $��$ photoproduction near threshold was found to be the $3/2^+$ partial wave, which is primarily due to the sub-threshold $N(1720)\,3/2^+$ resonance. At higher energies, pomeron-exchange was found to dominate whereas $��$-exchange remained small. These $t$-channel contributions as well as further contributions from nucleon resonances were necessary to describe the entire dataset: the $1/2^-$, $3/2^-$, and $5/2^+$ partial waves were also found to contribute significantly., 8 pages, 5 figures, accepted for publication in Physics Letters B

Published
2015
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3. High statistics study of the reaction $��p\to p\;2��^0$

Author

Sokhoyan, V., Gutz, E., Crede, V., van Pee, H., Anisovich, A. V., Bacelar, J. C. S., Bantes, B., Bartholomy, O., Bayadilov, D., Beck, R., Beloglazov, Y. A., Castelijns, R., Dutz, H., Elsner, D., Ewald, R., Frommberger, F., Fuchs, M., Funke, Ch., Gregor, R., Gridnev, A. B., Hillert, W., Hoffmeister, Ph., Horn, I., Jaegle, I., Junkersfeld, J., Kalinowsky, H., Kammer, S., Kleber, V., Klein, Frank, Klein, Friedrich, Klempt, E., Kotulla, M., Krusche, B., Lang, M., L��hner, H., Lopatin, I. V., Lugert, S., Mertens, T., Messchendorp, J. G., Metag, V., Metsch, B., Nanova, M., Nikonov, V. A., Novinsky, D., Novotny, R., Ostrick, M., Pant, L., Pfeiffer, M., Piontek, D., Roy, A., Sarantsev, A. V., Schmidt, Ch., Schmieden, H., Seifen, T., Shende, S., S��le, A., Sumachev, V. V., Szczepanek, T., Thiel, A., Thoma, U., Trnka, D., Varma, R., Walther, D., Wendel, Ch., and Wilson, A.

Subjects
FOS: Physical sciences, Nuclear Experiment (nucl-ex)
Abstract

The photoproduction of 2$��^0$ mesons off protons was studied with the Crystal Barrel/TAPS experiment at the electron accelerator ELSA in Bonn. The energy of photons produced in a radiator was tagged in the energy range from 600\,MeV to 2.5\,GeV. Differential and total cross sections and $p��^0��^0$ Dalitz plots are presented. Part of the data was taken with a diamond radiator producing linearly polarized photons, and beam asymmetries were derived. Properties of nucleon and $��$ resonances contributing to the $p��^0��^0$ final state were determined within the BnGa partial wave analysis. The data presented here allow us to determine branching ratios of nucleon and $��$ resonances for their decays into $p��^0��^0$ via several intermediate states. Most prominent are decays proceeding via $��(1232)��$, $N(1440)1/2^+��$, $N(1520)3/2^-��$, $N(1680)5/2^+��$, but also $pf_0(500)$, $pf_0(980)$, and $pf_2(1270)$ contribute to the reaction., 28 pages, 17 figures, 7 tables

Published
2015
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4. Determination of the �� mass with the Crystal Ball at MAMI-B

Author

Nikolaev, A., Aguar-Bartolom��, P., Ahrens, J., Annand, J. R. M., Arends, H. J., Beck, R., Bekrenev, V., Boillat, B., Braghieri, A., Branford, D., Briscoe, W. J., Brudvik, J. W., Cherepnya, S., Codling, R., Dehn, M., Downie, E. J., Fil'kov, L. V., Glazier, D. I., Gregor, R., Heid, E., Hornidge, D., Jahn, O., Jankowiak, A., Kaiser, K. -H., Kashevarov, V. L., Kondratiev, R., Korolija, M., Kotulla, M., Krambrich, D., Krusche, B., Lang, M., Lisin, V., Livingston, K., Ludwig-Mertin, U., Lugert, S., MacGregor, I. J. D., Manley, D. M., Martinez-Fabregate, M., McGeorge, J. C., Mekterovic, D., Metag, V., Nefkens, B. M. K., Novotny, R., Owens, R. O., Pedroni, P., Polonski, A., Prakhov, S. N., Price, J. W., Reiter, A., Rosner, G., Rost, M., Rostomyan, T., Schumann, S., Sober, D., Starostin, A., Supek, I., Tarbert, C. M., Thomas, A., Unverzagt, M., Walcher, Th., Watts, D. P., and Zehr, F.

Subjects
FOS: Physical sciences, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

A new precise determination of the �� meson mass is presented. It is based on a measurement of the threshold for the ��p -> p�� reaction using the tagger focal-plane microscope detector at the MAMI-B facility in Mainz. The tagger microscope has a higher energy resolution than the standard tagging spectrometer and, hence, allowed an improvement in the accuracy compared to the previous �� mass measurement at MAMI-B. The result m�� = (547.851 +- 0.031 stat. +- 0.062 syst.) MeV agrees very well with the precise values of the NA48, KLOE and CLEO collaborations and deviates by about 5�� from the smaller, but also very precise value obtained by the GEM collaboration at COSY., Submitted for publication in EPJA

Published
2012
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5. Photoproduction of $��$ mesons on nuclei near the production threshold

Author

Nanova, M., Weil, J., Friedrich, S., Metag, V., Mosel, U., Anton, G., Bacelar, J. C. S., Bartholomy, O., Bayadilov, D., Beloglazov, Y. A., Bogend��rfer, R., Castelijns, R., Crede, V., Dutz, H., Ehmanns, A., Elsner, D., Essig, K., Ewald, R., Fabry, I., Fuchs, M., Funke, Ch., Gothe, R., Gregor, R., Gridnev, A. B., Gutz, E., H��ffgen, S., Hoffmeister, P., Horn, I., H��ssl, J., Jaegle, I., Junkersfeld, J., Kalinowsky, H., Klein, Frank, Klein, Friedrich, Klempt, E., Konrad, M., Kopf, B., Kotulla, M., Krusche, B., Langheinrich, J., L��hner, H., Lopatin, I. V., Lotz, J., Lugert, S., Menze, D., Mertens, T., Messchendorp, J. G., Morales, C., Novotny, R., Ostrick, M., Pant, L. M., van Pee, H., Pfeiffer, M., Roy, A., Radkov, A., Schadmand, S., Schmidt, Ch., Schmieden, H., Schoch, B., Shende, S., Suft, G., S��le, A., Sumachev, V. V., Szczepanek, T., Thoma, U., Trnka, D., Varma, R., Walther, D., Weinheimer, Ch., and Wendel, Ch.

Subjects
Nuclear Theory, FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

The photoproduction of $��$ mesons on LH_2, C and Nb has been studied for incident photon energies from 900 to 1300 MeV using the CB/TAPS detector at ELSA. The $��$ line shape does not show any significant difference between the LH_2 and the Nb targets. The data are compared with results of transport calculations that predict a sensitivity of the $��$ line shape to in-medium modifications near the production threshold on a free nucleon of $E_��^{lab}$ = 1109 MeV.}, 5 pages, 3 figures

Published
2010
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6. Measurement of the Beam Asymmetry $��$ in the Forward Direction for pi0 Photoproduction

Author

Sparks, N., Crede, V., Anisovich, A. V., Bacelar, J. C. S., Bantes, R., Bartholomy, O., Bayadilov, D., Beck, R., Beloglazov, Y. A., Castelijns, R., Elsner, D., Ewald, R., Frommberger, F., Funke, C., Gregor, R., Gridnev, A., Gutz, E., Hillert, W., Hoffmeister, P., Jaegle, I., Junkersfeld, J., Kalinowsky, H., Kammer, S., Klein, Frank, Klein, Friedrich, Klempt, E., Kotulla, M., Krusche, B., Loehner, H., Lopatin, I. V., Lugert, S., Menze, D., Mertens, T., Messchendorp, J. G., Metag, V., Nanova, M., Nikonov, V. A., Novinski, D., Novotny, R., Ostrick, M., Pant, L. M., Pee, H., Pfeiffer, M., Roy, A., Sarantsev, A. V., Schadmand, S., Schmidt, C., Schmieden, H., Schoch, B., Shende, S., Sokhoyan, V., Suele, A., Sumachev, V. V., Szczepanek, T., Thoma, U., Trnka, D., Varma, R., Walther, D., Wendel, C., and Wilson, A.

Subjects
High Energy Physics - Experiment (hep-ex), FOS: Physical sciences, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

Photoproduction of neutral pions has been studied with the CBELSA/TAPS detector for photon energies between 0.92 and 1.68~GeV at the electron accelerator ELSA. The beam asymmetry~$��$ has been extracted for $115^\circ < ��_{\rm c.m.} < 155^\circ$ of the $��^0$~meson and for $��_{\rm c.m.} < 60^\circ$. The new beam asymmetry data improve the world database for photon energies above 1.5~GeV and, by covering the very forward region, extend previously published data for the same reaction by our collaboration. The angular dependence of $��$ shows overall good agreement with the SAID parameterization., 11 pages, 10 figures, published in Phys. Rev. C, included LEPS data and MAID 2007 predictions for comparison with our data

Published
2010
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7. Photoproduction of $��'$-mesons off the deuteron

Author

Jaegle, I., Mertens, T., Fix, A., Huang, F., Nakayama, K., Tiator, L., Anisovich, A. V., Bacelar, J. C. S., Bantes, B., Bartholomy, O., Bayadilov, D. E., Beck, R., Beloglazov, Y. A., Castelijns, R., Crede, V., Dutz, H., Elsner, D., Ewald, R., Frommberger, F., Funke, C., Gregor, R., Gridnev, A. B., Gutz, E., Hillert, W., Hoeffgen, S., Junkersfeld, J., Kalinowsky, H., Kammer, S., Kleber, V., Klein, Frank, Klein, Friedrich, Klempt, E., Kotulla, M., Krusche, B., Lang, M., Loehner, H., Lopatin, I. V., Lugert, S., Menze, D., Messchendorp, J. G., Metag, V., Nikonov, V. A., Nanova, M., Novinski, D. V., Novotny, R., Ostrick, M., Pant, L. M., van Pee, H., Pfeiffer, M., Roy, A., Sarantsev, A. V., Schadmand, S., Schmidt, C., Schmieden, H., Schoch, B., Shende, S. V., Sokhoyan, V., Suele, A., Sumachev, V. V., Szczepanek, T., Thoma, U., Trnka, D., Varma, R., Walther, D., and Wendel, C.

Subjects
Nuclear Theory, FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

Quasi-free photoproduction of $��'$ mesons off nucleons bound in the deuteron has been measured with the combined Crystal Barrel - TAPS detector. The experiment was done at a tagged photon beam of the ELSA electron accelerator in Bonn for incident photon energies from the production threshold up to 2.5 GeV. The $��'$-mesons have been detected in coincidence with recoil protons and recoil neutrons. The quasi-free proton data are in good agreement with the results for free protons, indicating that nuclear effects have no significant impact. The coincidence with recoil neutrons provides the first data for the $��n \rightarrow n��'$ reaction. In addition, also first estimates for coherent $��'$-production off the deuteron have been obtained. In agreement with model predictions, the total cross section for this channel is found to be very small, at most at the level of a few nb. The data are compared to model calculations taking into account contributions from nucleon resonances and $t$-channel exchanges., Accepted for publication in Eur. Phys. J. A

Published
2010
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8. In-medium $��$ mass from the $��+ Nb \to ��^{0}��+ X$ reaction

Author

TAPS Collaboration, Nanova, M., Metag, V., Anton, G., Bacelar, J. C. S., Bartholomy, O., Bayadilov, D., Beloglazov, Y. A., Bogend��rfer, R., Castelijns, R., Crede, V., Dutz, H., Ehmanns, A., Elsner, D., Essig, K., Ewald, R., Fabry, I., Fuchs, M., Funke, Ch., Gothe, R., Gregor, R., Gridnev, A. B., Gutz, E., H��ffgen, S., Hoffmeister, P., Horn, I., H��ssl, J., Jaegle, I., Junkersfeld, J., Kalinowsky, H., Klein, Frank, Klein, Friedrich, Klempt, E., Konrad, M., Kopf, B., Kotulla, M., Krusche, B., Langheinrich, J., L��hner, H., Lopatin, I. V., Lotz, J., Lugert, S., Menze, D., Mertens, T., Messchendorp, J. G., Morales, C., Novotny, R., Ostrick, M., Pant, L. M., van Pee, H., Pfeiffer, M., Roy, A., Radkov, A., Schadmand, S., Schmidt, Ch., Schmieden, H., Schoch, B., Shende, S., Suft, G., S��le, A., Sumachev, V. V., Szczepanek, T., Thoma, U., Trnka, D., Varma, R., Walther, D., Weinheimer, Ch., and Wendel, Ch.

Subjects
FOS: Physical sciences, Nuclear Experiment (nucl-ex)
Abstract

Data on the photoproduction of $��$ mesons on nuclei have been re-analyzed in a search for in-medium modifications. The data were taken with the Crystal Barrel(CB)/TAPS detector system at the ELSA accelerator facility in Bonn. First results from the analysis of the data set were published by D. Trnka et al. in Phys. Rev. Lett 94 (2005) 192303 \cite{david}, claiming a lowering of the $��$ mass in the nuclear medium by 14$%$ at normal nuclear matter density. The extracted $��$ line shape was found to be sensitive to the background subtraction. For this reason a re-analysis of the same data set has been initiated and a new method has been developed to reduce the background and to determine the shape and absolute magnitude of the background directly from the data. Details of the re-analysis and of the background determination are described. The $��$ signal on the $Nb$ target, extracted in the re-analysis, does not show a deviation from the corresponding line shape on a $LH_2$ target, measured as reference. The earlier claim of an in-medium mass shift is thus not confirmed. The sensitivity of the $��$ line shape to different in-medium modification scenarios is discussed., 13 pages and 11 figures, submitted for publication

Published
2010
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9. Determination of the Dalitz plot parameter alpha for the decay eta->3pi^0 with the Crystal Ball at MAMI-B

Author

Unverzagt, M., Aguar-Bartolome, P., Ahrens, J., Annand, J. R. M., Arends, H. J., Beck, R., Bekrenev, V., Boillat, B., Braghieri, A., Branford, D., Briscoe, W. J., Brudvik, J. W., Cherepnya, S., Codling, R., Downie, E. J., Filkov, L. V., Glazier, D. I., Gregor, R., Heid, E., Hornidge, D., Jahn, O., Kashevarov, V. L., Kondratiev, R., Korolija, M., Kotulla, M., Krambrich, D., Krusche, B., Lang, M., Lisin, V., Livingston, K., Lugert, S., MacGregor, I. J. D., Manley, D. M., Martinez-Fabregate, M., McGeorge, J. C., Mekterovic, D., Metag, V., Nefkens, B. M. K., Nikolaev, A., Novotny, R., Owens, R. O., Pedroni, P., Polonski, A., Prakhov, S. N., Price, J. W., Rosner, G., Rost, M., Rostomyan, T., Schumann, S., Sober, D., Starostin, A., Supek, I., Tarbert, C. M., Thomas, A., Walcher, Th., Watts, D. P., and Zehr, F.

Subjects
High Energy Physics - Experiment (hep-ex), FOS: Physical sciences, High Energy Physics::Experiment, Nuclear Experiment
Abstract

A precise measurement of the Dalitz plot parameter, alpha, for the eta->3pi^0 decay is presented. The experiment was performed with the Crystal Ball and TAPS large acceptance photon detectors at the tagged photon beam facility of the MAMI-B electron accelerator in Mainz. High statistics of 1.8*10^6 eta->3pi^0 events were obtained, giving the result alpha = -0.032 +/- 0.002(stat) +/- 0.002(syst)., 9 pages, 6 figures, published in the online-first section of EPJ A, included changes referees asked for, added DOI

Published
2008
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10. Quasi-free photoproduction of eta-mesons of the neutron

Author

Jaegle, I., Mertens, T., Anisovich, A. V., Bacelar, J. C. S., Bantes, B., Bartholomy, O., Bayadilov, D., Beck, R., Beloglazov, Y. A., Castelijns, R., Crede, V., Dutz, H., Ehmanns, A., Elsner, D., Essig, K., Ewald, R., Fabry, I., Fuchs, M., Funke, C., Gothe, R., Gregor, R., Gridnev, A. B., Gutz, E., Hoeffgen, S., Hoffmeister, P., Horn, I., Junkersfeld, J., Kalinowsky, H., Kammer, S., Kleber, V., Klein, Frank, Klein, Friedrich, Klempt, E., Konrad, M., Kotulla, M., Krusche, B., Lang, M., Langheinrich, J., Loehner, H., Lopatin, I. V., Lotz, J., Lugert, S., Menze, D., Messchendorp, J. G., Metag, V., Morales, C., Nanova, M., Nikonov, V. A., Novinski, D. V., Novotny, R., Ostrick, M., Pant, L. M., van Pee, H., Pfeiffer, M., Radkov, A. K., Roy, A., Sarantsev, A. V., Schadmand, S., Schmidt, C., Schmieden, H., Schoch, B., Shende, S., Sokhoyan, V., Suele, A., Sumachev, V. V., Szczepanek, T., Thoma, U., Trnka, D., Varma, R., Walther, D., Weinheimer, C., and Wendel, C.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Nuclear Theory, FOS: Physical sciences, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

Quasi-free photoproduction of eta-mesons off nucleons bound in the deuteron has been measured with the CBELSA/TAPS detector for incident photon energies up to 2.5 GeV at the Bonn ELSA accelerator. The eta-mesons have been detected in coincidence with recoil protons and recoil neutrons, which allows a detailed comparison of the quasi-free n(gamma,eta)n and p(gamma,eta)p reactions. The excitation function for eta-production off the neutron shows a pronounced bump-like structure at W=1.68 GeV (E_g ~ 1 GeV), which is absent for the proton., Comment: accepted for publication in Phys. Rev. Lett

Published
2008
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11. Modification of the $��$-Meson Lifetime in Nuclear Matter

Author

Kotulla, M., Trnka, D., M��hlich, P., Anton, G., Bacelar, J. C. S., Bartholomy, O., Bayadilov, D., Beloglazov, Y. A., Bogend��rfer, R., Castelijns, R., Crede, V., Dutz, H., Ehmanns, A., Elsner, D., Ewald, R., Fabry, I., Fuchs, M., Essig, K., Funke, Ch., Gothe, R., Gregor, R., Gridnev, A. B., Gutz, E., H��ffgen, S., Hoffmeister, P., Horn, I., H��ssl, J., Jaegle, I., Junkersfeld, J., Kalinowsky, H., Klein, Frank, Klein, Fritz, Klempt, E., Konrad, M., Kopf, B., Krusche, B., Langheinrich, J., L��hner, H., Lopatin, I. V., Lotz, J., Lugert, S., Menze, D., Messchendorp, J. G., Mertens, T., Metag, V., Mosel, U., Nanova, M., Novotny, R., Ostrick, M., Pant, L. M., van Pee, H., Pfeiffer, M., Roy, A., Radkov, A., Schadmand, S., Schmidt, Ch., Schmieden, H., Schoch, B., Shende, S., Suft, G., Sumachev, V. V., Szczepanek, T., S��le, A., Thoma, U., Varma, R., Walther, D., Weinheimer, Ch., and Wendel, Ch.

Subjects
Nuclear Theory (nucl-th), High Energy Physics - Phenomenology (hep-ph), Nuclear Theory, FOS: Physical sciences, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

The photo production of $��$ mesons on the nuclei C, Ca, Nb and Pb has been measured using the Crystal Barrel/TAPS detector at the ELSA tagged photon facility in Bonn. The dependence of the $��$ meson cross section on the nuclear mass number has been compared with three different types of models, a Glauber analysis, a BUU analysis of the Giessen theory group and a calculation by the Valencia theory group. In all three cases, the inelastic $��$ width is found to be $130-150 \rm{MeV/c^2}$ at normal nuclear matter density for an average 3-momentum of 1.1 GeV/c. In the restframe of the $��$ meson, this inelastic $��$ width corresponds to a reduction of the $��$ lifetime by a factor $\approx 30$. For the first time, the momentum dependent $��$N cross section has been extracted from the experiment and is in the range of 70 mb., 5 pages, 4 figures

Published
2008
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12. Photoproduction of eta-mesons off nuclei for Eg < 2.2 GeV

Author

Mertens, T., Jaegle, I., Muehlich, P., Bacelar, J. C. S., Bantes, B., Bartholomy, O., Bayadilov, D. E., Beck, R., Beloglazov, Y. A., Castelijns, R., Crede, V., Dutz, H., Ehmanns, A., Elsner, D., Essig, K., Ewald, R., Fabry, I., Fornet-Ponse, K., Fuchs, M., Funke, C., Gothe, R., Gregor, R., Gridnev, A. B., Gutz, E., Hoeffgen, S., Hoffmeister, P., Horn, I., Junkersfeld, J., Kalinowsky, H., Kammer, S., Kleber, V., Klein, Frank, Klein, Friedrich, Klempt, E., Konrad, M., Kotulla, M., Krusche, B., Lang, M., Langheinrich, J., Loehner, H., Lopatin, I. V., Lotz, J., Lugert, S., Menze, D., Messchendorp, J. G., Metag, V., Morales, C., Mosel, U., Nanova, M., Novinski, D. V., Novotny, R., Ostrick, M., Pant, L. M., van Pee, H., Pfeiffer, M., Radkov, A. K., Roy, A., Schadmand, S., Schmidt, C., Schmieden, H., Schoch, B., Shende, S., Sokhoyan, V., Suele, A., Sumachev, V. V., Szczepanek, T., Thoma, U., Trnka, D., Varma, R., Walther, D., Weinheimer, C., and Wendel, C.

Subjects
Nuclear Theory, FOS: Physical sciences, High Energy Physics::Experiment, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

Photoproduction of $��$ mesons off $^{12}$C, $^{40}$Ca, $^{93}$Nb, and $^{nat}$Pb nuclei has been measured with a tagged photon beam with energies between 0.6 and 2.2 GeV. The experiment was performed at the Bonn ELSA accelerator with the combined setup of the Crystal Barrel and TAPS calorimeters. It aimed at the in-medium properties of the S$_{11}$(1535) nucleon resonance and the study of the absorption properties of nuclear matter for $��$ mesons. Careful consideration was given to contributions from $����$ final states and secondary production mechanisms of $��$-mesons e.g. from inelastic $��N$ reactions of intermediate pions. The analysis of the mass number scaling shows that the nuclear absorption cross section $��_{N��}$ for $��$ mesons is constant over a wide range of the $��$ momentum. The comparison of the excitation functions to data off the deuteron and to calculations in the framework of a BUU-model show no unexplained in-medium modifications of the S$_{11}$(1535)., Accepted for publication in Eur. Phys. J. A

Published
2008
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13. Incoherent pion photoproduction on $^{12}$C

Author

Tarbert, C. M., Watts, D. P., Aguar, P., Ahrens, J., Annand, J. R. M., Arends, H. J., Beck, R., Bekrenev, V., Boillat, B., Braghieri, A., Branford, D., Briscoe, W. J., Brudvik, J., Cherepnya, S., Codling, R., Downie, E. J., Foehl, K., Glazier, D. I., Grabmayr, P., Gregor, R., Heid, E., Hornidge, D., Jahn, O., Kashevarov, V. L., Knezevic, A., Kondratiev, R., Korolija, M., Kotulla, M., Krambrich, D., Krusche, B., Lang, M., Lisin, V., Livingston, K., Lugert, S., MacGregor, I. J. D., Manley, D. M., Martinez, M., McGeorge, J. C., Mekterovic, D., Metag, V., Nefkens, B. M. K., Nikolaev, A., Novotny, R., Owens, R. O., Pedroni, P., Polonski, A., Prakhov, S. N., Price, J. W., Rosner, G., Rost, M., Rostomyan, T., Schadmand, S., Schumann, S., Sober, D., Starostin, A., Supek, I., Thomas, A., Unverzagt, M., Walcher, Th., and Zehr, F.

Subjects
Nuclear Theory, FOS: Physical sciences, Nuclear Experiment (nucl-ex), Nuclear Experiment
Abstract

We present the first detailed measurement of incoherent photoproduction of neutral pions to a discrete state of a residual nucleus. The $^{12}$C$(\gamma,\pi^{0})^{12}$C$^{*}_{4.4MeV}$ reaction has been studied with the Glasgow photon tagger at MAMI employing a new technique which uses the large solid angle Crystal Ball detector both as a $\pi^{0}$ spectrometer and to detect decay photons from the excited residual nucleus. The technique has potential applications to a broad range of future nuclear measurements with the Crystal Ball and similar detector systems elsewhere. The data are sensitive to the propagation of the $\Delta$ in the nuclear medium and will give the first information on matter transition form factors from measurements with an electromagnetic probe. The incoherent cross sections are compared to two theoretical predictions including a $\Delta$-hole model., Comment: 4 pages, 8 figures, submitted to Physical Review Letters

Published
2007
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14. First observation of in-medium modifications of the omega meson

Author

Trnka, D., Anton, G., Bacelar, J.C.S, Bartholomy, O., Bayadilov, D., Beloglazov, Y.A., Bogendorfer, R., Castelijns, R.J.J., Crede, V., Dutz, H., Ehmanns, A., Elsner, D., Ewald, R., Fabry, I., Fuchs, M., Essig, K., Funke, Ch., Gothe, R., Gregor, R., Gridnev, A., Gutz, E., Hoffgen, S.K., Hoffmeister, P., Horn, I., Hössl, J., Jaegle, I., Junkersfeld, J., Kalinowsky, H., Klein, Frank, Klein, Fritz, Klempt, E., Konrad, M., Kopf, B., Kotulla, M., Krusche, B., Langheinrich, J., Löhner, H., Lopatin, I., Lotz, J., Lugert, S., Menze, D.W., Messchendorp, J.G., Mertens, T., Metag, V., Morales, C., Nanova, M., Novotny, R., Ostrick, M., Pant, L.M., van Pee, H., Pfeiffer, M., Roy, A., Radkov, A., Schadmand, S., Schmidt, Ch., Schmieden, H., Schoch, B., Shende, S., Suft, G., Sumachev, V., Szczepanek, T., Sule, A., Thoma, U., Varma, R., Walther, D., Weinheimer, Ch., Wendel, Ch., and KVI - Center for Advanced Radiation Technology

Subjects
JONA-LASINIO MODEL, deuteron, +pi0+photon%22">omega(783) --> pi0 photon, Nuclear Theory, FOS: Physical sciences, (pi0 photon) [mass spectrum], +omega%28783%29+anything%22">photon nucleus --> omega(783) anything, 0.64-2.53 GeV, High Energy Physics - Experiment, Nuclear Theory (nucl-th), High Energy Physics - Experiment (hep-ex), ddc:550, Bonn ELSA Stor, SPECTROMETER, density [nuclear matter], Nuclear Experiment (nucl-ex), Nuclear Experiment, AU COLLISIONS, mass [omega(783)], NUCLEI, PAIRS, momentum [omega(783)], radiative decay [omega(783)], High Energy Physics::Experiment, photoproduction [omega(783)], inclusive reaction [photon nucleus], NAMBU, niobium, VECTOR-MESONS, MATTER, experimental results
Abstract

The photoproduction of omega mesons on nuclei has been investigated using the Crystal Barrel/TAPS experiment at the ELSA tagged photon facility in Bonn. The aim is to study possible in-medium modifications of the omega meson via the reaction A(gamma, omega)X. Results obtained for Nb are compared to a reference measurement on a liquid hydrogen target. While for recoiling, long-lived mesons (pi, eta and etaprime), which decay outside of the nucleus, a difference in the lineshape for the two data samples is not observed, we find a significant enhancement towards lower masses for omega mesons with low momenta produced on the Nb target., Comment: Latex, 4 pages, 4 figures, accepted by Phys. Rev. Lett; references re-arranged, now references in chronological order in first paragraph

Published
2005
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