/ Experiment-HEP arXiv:1205.1918

First measurement of low momentum dielectrons radiated off cold nuclear matter

Agakishiev, G. (Dubna, JINR) ; Balanda, A. (Jagiellonian U.) ; Belver, D. (Santiago de Compostela U.) ; Belyaev, A. (Dubna, JINR) ; Berger-Chen, J.C. (Munich U.) ; Blanco, A. (Lisbon, LIFEP) ; Bohmer, M. (Munich, Tech. U.) ; Boyard, J.L. (Orsay, IPN) ; Cabanelas, P. (Santiago de Compostela U.) ; Chernenko, S. (Dubna, JINR) ; Dybczak, A. (Jagiellonian U.) ; Epple, E. (Munich U.) ; Fabbietti, L. (Munich U.) ; Fateev, O. (Dubna, JINR) ; Finocchiaro, P. (INFN, Catania) ; Fonte, P. (Coimbra Inst. Sup. Eng.) ; Friese, J. (Munich, Tech. U.) ; Frohlich, I. (Frankfurt U.) ; Galatyuk, T. (Darmstadt, EMMI) ; Garzon, J.A. (Santiago de Compostela U.) ; Gernhauser, R. (Munich, Tech. U.) ; Gobel, K. (Frankfurt U.) ; Golubeva, M. (Moscow, INR) ; Gonzalez-Diaz, D. (Darmstadt, Tech. Hochsch.) ; Guber, F. (Moscow, INR) ; Gumberidze, M. (Orsay, IPN) ; Heinz, T. (Darmstadt, GSI) ; Hennino, T. (Orsay, IPN) ; Holzmann, R. (Darmstadt, GSI) ; Ierusalimov, A. (Dubna, JINR) ; Iori, I. (Milan U.) ; Ivashkin, A. (Moscow, INR) ; Jurkovic, M. (Munich, Tech. U.) ; Kampfer, B. (Dresden, Tech. U.) ; Karavicheva, T. (Moscow, INR) ; Koenig, I. (Darmstadt, GSI) ; Koenig, W. (Darmstadt, GSI) ; Kolb, B.W. (Darmstadt, GSI) ; Kornakov, G. (Santiago de Compostela U.) ; Kotte, R. (Forschungszentrum Dresden Rossendorf) ; Krasa, A. (Rez, Nucl. Phys. Inst.) ; Krizek, F. (Rez, Nucl. Phys. Inst.) ; Krucken, R. (Munich, Tech. U.) ; Kuc, H. (Orsay, IPN) ; Kuhn, W. (Giessen U.) ; Kugler, A. (Rez, Nucl. Phys. Inst.) ; Kurepin, A. (Moscow, INR) ; Ladygin, V. (Dubna, JINR) ; Lalik, R. (Munich U.) ; Lang, S. (Darmstadt, GSI) ; Lapidus, K. (Munich U.) ; Lebedev, A. (Moscow, ITEP) ; Liu, T. (Orsay, IPN) ; Lopes, L. (Lisbon, LIFEP) ; Lorenz, M. (Frankfurt U.) ; Maier, L. (Munich, Tech. U.) ; Mangiarotti, A. (Lisbon, LIFEP) ; Markert, J. (Frankfurt U.) ; Metag, V. (Giessen U.) ; Michalska, B. (Jagiellonian U.) ; Michel, J. (Frankfurt U.) ; Muntz, C. (Frankfurt U.) ; Naumann, L. (Forschungszentrum Dresden Rossendorf) ; Pachmayer, Y.C. (Frankfurt U.) ; Palka, M. (Jagiellonian U.) ; Parpottas, Y. (UC, Irvine) ; Pechenov, V. (Darmstadt, GSI) ; Pechenova, O. (Frankfurt U.) ; Pietraszko, J. (Frankfurt U.) ; Przygoda, W. (Jagiellonian U.) ; Ramstein, B. (Orsay, IPN) ; Reshetin, A. (Moscow, INR) ; Rustamov, A. (Frankfurt U.) ; Sadovsky, A. (Moscow, INR) ; Salabura, P. (Jagiellonian U.) ; Schmah, A. (LBL, Berkeley) ; Schwab, E. (Darmstadt, GSI) ; Siebenson, J. (Munich U.) ; Sobolev, Yu.G. (Rez, Nucl. Phys. Inst.) ; Spataro, S. (INFN, Turin) ; Spruck, B. (Giessen U.) ; Strobele, H. (Frankfurt U.) ; Stroth, J. (Darmstadt, GSI) ; Sturm, C. (Darmstadt, GSI) ; Tarantola, A. (Frankfurt U.) ; Teilab, K. (Frankfurt U.) ; Tlusty, P. (Rez, Nucl. Phys. Inst.) ; Traxler, M. (Darmstadt, GSI) ; Trebacz, R. (Jagiellonian U.) ; Tsertos, H. (Cyprus U.) ; Vasiliev, T. (Dubna, JINR) ; Wagner, V. (Rez, Nucl. Phys. Inst.) ; Weber, M. (Houston U.) ; Wendisch, C. (Forschungszentrum Dresden Rossendorf) ; Wustenfeld, J. (Forschungszentrum Dresden Rossendorf) ; Yurevich, S. (Darmstadt, GSI) ; Zanevsky, Y. (Houston U.)

Abstract: We present data on dielectron emission in proton induced reactions on a Nb target at 3.5 GeV kinetic beam energy measured with HADES installed at GSI. The data represent the first high statistics measurement of dielectrons radiated from cold nuclear matter in a kinematic regime, where strong medium effects are expected. Combined with the good mass resolution of 2%, it is the first measurement sensitive to changes of the spectral functions of vector mesons, as predicted by models for hadrons at rest or small relative momenta. Comparing the e+e- invariant mass spectra to elementary p+p data, we observe for e+e- momenta P<0.8 GeV/c a strong modification of the shape of the spectra, which we attribute to an additional rho-like contribution and a decrease in omega yield. These opposite trends are tentatively interpreted as a strong coupling of the rho meson to baryonic resonances and an absorption of the omega meson, which are two aspects of in-medium modification of vector mesons.

Web-Page: http://inspirehep.net/record/1114033/files/arXiv:1205.1918.pdf; http://inspirehep.net/record/1114033/files/RpA_new.png; http://inspirehep.net/record/1114033/files/cross_v6.png; http://inspirehep.net/record/1114033/files/excess_V7_shaded.png; http://inspirehep.net/record/1114033/files/fast.png; http://inspirehep.net/record/1114033/files/slow.png; http://inspirehep.net/record/1114033/files/slow_liinV6.png

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