/ Experiment-HEP arXiv:0901.1015


Angular distributions of leptons from J/psi's produced in 920- GeV fixed-target proton-nucleus collisions


Abt, I. (Munich, Max Planck Inst.) ; Adams, M. (Dortmund U.) ; Agari, M. (Heidelberg, Max Planck Inst.) ; Albrecht, H. (DESY) ; Aleksandrov, A. (DESY, Zeuthen) ; Amaral, V. (LIP, Coimbra) ; Amorim, A. (LIP, Coimbra) ; Aplin, S.J. (DESY) ; Aushev, V. (Kiev, INR) ; Bagaturia, Y. (Tbilisi State U.) ; Balagura, V. (Moscow, ITEP) ; Bargiotti, M. (INFN, Bologna) ; Barsukova, O. (Dubna, JINR) ; Bastos, J. (LIP, Coimbra) ; Batista, J. (LIP, Coimbra) ; Bauer, C. (Heidelberg, Max Planck Inst.) ; Bauer, Th.S. (NIKHEF, Amsterdam) ; Belkov, A. (Dubna, JINR) ; Belkov, Ar. (Dubna, JINR) ; Belotelov, I. (Dubna, JINR) ; Bertin, A. (INFN, Bologna) ; Bobchenko, B. (Moscow, ITEP) ; Bocker, M. (Siegen U.) ; Bogatyrev, A. (Moscow, ITEP) ; Bohm, G. (DESY, Zeuthen) ; Brauer, M. (Heidelberg, Max Planck Inst.) ; Bruinsma, M. (NIKHEF, Amsterdam) ; Bruschi, M. (INFN, Bologna) ; Buchholz, P. (Siegen U.) ; Buran, T. (Oslo U.) ; Carvalho, J. (LIP, Coimbra) ; Conde, P. (DESY) ; Cruse, C. (Dortmund U.) ; Dam, M. (Bohr Inst.) ; Danielsen, K.M. (Oslo U.) ; Danilov, M. (Moscow, ITEP) ; De Castro, S. (INFN, Bologna) ; Deppe, H. (Heidelberg U.) ; Dong, X. (Beijing, Inst. High Energy Phys.) ; Dreis, H.B. (Heidelberg U.) ; Egorytchev, V. (DESY) ; Ehret, K. (Dortmund U.) ; Eisele, F. (Heidelberg U.) ; Emeliyanov, D. (DESY) ; Essenov, S. (Moscow, ITEP) ; Fabbri, L. (INFN, Bologna) ; Faccioli, P. (INFN, Bologna) ; Feuerstack-Raible, M. (Heidelberg U.) ; Flammer, J. (DESY) ; Fominykh, B. (Moscow, ITEP) ; Funcke, M. (Dortmund U.) ; Garrido, Ll. (Barcelona U., ECM) ; Gellrich, A. (DESY, Zeuthen) ; Giacobbe, B. (INFN, Bologna) ; Glass, J. (Mannheim U.) ; Goloubkov, D. (Moscow Phys. Eng. Inst.) ; Golubkov, Y. (Moscow State U.) ; Golutvin, A. (Moscow, ITEP) ; Golutvin, I. (Dubna, JINR) ; Gorbounov, I. (Siegen U.) ; Gorisek, A. (Stefan Inst., Ljubljana) ; Gouchtchine, O. (Moscow, ITEP) ; Goulart, D.C. (Cincinnati U.) ; Gradl, S. (Heidelberg U.) ; Gradl, W. (Heidelberg U.) ; Grimaldi, F. (INFN, Bologna) ; Groth-Jensen, J. (Bohr Inst.) ; Guilitsky, Yu. (Serpukhov, IHEP) ; Hansen, J.D. (Bohr Inst.) ; Hernandez, J.M. (DESY, Zeuthen) ; Hofmann, W. (Heidelberg, Max Planck Inst.) ; Hohlmann, M. (DESY) ; Hott, T. (Heidelberg U.) ; Hulsbergen, W. (NIKHEF, Amsterdam) ; Husemann, U. (Siegen U.) ; Igonkina, O. (Moscow, ITEP) ; Ispiryan, M. (Houston U.) ; Jagla, T. (Heidelberg, Max Planck Inst.) ; Jiang, C. (Beijing, Inst. High Energy Phys.) ; Kapitza, H. (Dortmund U.) ; Karabekyan, S. (Rostock U.) ; Karpenko, N. (Dubna, JINR) ; Keller, S. (Siegen U.) ; Kessler, J. (Heidelberg U.) ; Khasanov, F. (Moscow, ITEP) ; Kiryushin, Yu. (Dubna, JINR) ; Kisel, I. (Munich, Max Planck Inst.) ; Klinkby, E. (Bohr Inst.) ; Knopfle, K.T. (Heidelberg, Max Planck Inst.) ; Kolanoski, H. (Humboldt U., Berlin) ; Korpar, S. (Stefan Inst., Ljubljana) ; Krauss, C. (Heidelberg U.) ; Kreuzer, P. (UCLA) ; Krizan, P. (Stefan Inst., Ljubljana) ; Krucker, D. (Humboldt U., Berlin) ; Kupper, S. (Stefan Inst., Ljubljana) ; Kvaratskheliia, T. (Moscow, ITEP) ; Lanyov, A. (Dubna, JINR) ; Lau, K. (Houston U.) ; Lewendel, B. (DESY) ; Lohse, T. (Humboldt U., Berlin) ; Lomonosov, B. (Lebedev Inst.) ; Manner, R. (Mannheim U.) ; Mankel, R. (DESY, Zeuthen) ; Masciocchi, S. (DESY) ; Massa, I. (INFN, Bologna) ; Matchikhilian, I. (Moscow, ITEP) ; Medin, G. (Humboldt U., Berlin) ; Medinnis, M. (DESY) ; Mevius, M. (DESY) ; Michetti, A. (DESY) ; Mikhailov, Yu. (Serpukhov, IHEP) ; Mizuk, R. (Moscow, ITEP) ; Muresan, R. (Bohr Inst.) ; zur Nedden, M. (Humboldt U., Berlin) ; Negodaev, M. (Lebedev Inst.) ; Norenberg, M. (DESY) ; Nowak, S. (DESY, Zeuthen) ; Nunez Pardo de Vera, M.T. (DESY) ; Ouchrif, M. (NIKHEF, Amsterdam) ; Ould-Saada, F. (Oslo U.) ; Padilla, C. (DESY) ; Peralta, D. (Barcelona U., ECM) ; Pernack, R. (Rostock U.) ; Pestotnik, R. (Stefan Inst., Ljubljana) ; Petersen, B.AA. (Bohr Inst.) ; Piccinini, M. (INFN, Bologna) ; Pleier, Marc-Andre (Heidelberg, Max Planck Inst.) ; Poli, M. (Florence U., Dip. di Energetica) ; Popov, V. (Moscow, ITEP) ; Pose, D. (Heidelberg U.) ; Prystupa, S. (Kiev, INR) ; Pugatch, V. (Kiev, INR) ; Pylypchenko, Y. (Oslo U.) ; Pyrlik, J. (Houston U.) ; Reeves, K. (Heidelberg, Max Planck Inst.) ; Ressing, D. (DESY) ; Rick, H. (Heidelberg U.) ; Riu, I. (DESY) ; Robmann, P. (Zurich U.) ; Rostovtseva, I. (Moscow, ITEP) ; Rybnikov, V. (DESY) ; Sanchez, F. (Heidelberg, Max Planck Inst.) ; Sbrizzi, A. (NIKHEF, Amsterdam) ; Schmelling, M. (Heidelberg, Max Planck Inst.) ; Schmidt, B. (DESY) ; Schreiner, A. (DESY, Zeuthen) ; Schroder, H. (Rostock U.) ; Schwanke, U. (DESY, Zeuthen) ; Schwartz, A.J. (Cincinnati U.) ; Schwarz, A.S. (DESY) ; Schwenninger, B. (Dortmund U.) ; Schwingenheuer, B. (Heidelberg, Max Planck Inst.) ; Sciacca, F. (Heidelberg, Max Planck Inst.) ; Semprini-Cesari, N. (INFN, Bologna) ; Shuvalov, S. (Humboldt U., Berlin) ; Silva, L. (LIP, Coimbra) ; Sozuer, L. (DESY) ; Solunin, S. (Dubna, JINR) ; Somov, A. (DESY) ; Somov, S. (Moscow Phys. Eng. Inst.) ; Spengler, J. (DESY) ; Spighi, R. (INFN, Bologna) ; Spiridonov, A. (Moscow, ITEP) ; Stanovnik, A. (Stefan Inst., Ljubljana) ; Staric, M. (Stefan Inst., Ljubljana) ; Stegmann, C. (Humboldt U., Berlin) ; Subramania, H.S. (Houston U.) ; Symalla, M. (Dortmund U.) ; Tikhomirov, I. (Moscow, ITEP) ; Titov, Maxim P. (Moscow, ITEP) ; Tsakov, I. (Sofiya, Inst. Nucl. Res.) ; Uwer, U. (Heidelberg U.) ; van Eldik, C. (Dortmund U.) ; Vassiliev, Yu. (Kiev, INR) ; Villa, M. (INFN, Bologna) ; Vitale, A. (Fond. Giuseppe Occhialini) ; Vukotic, I. (DESY, Zeuthen) ; Wahlberg, H. (Utrecht U.) ; Walenta, A.H. (Siegen U.) ; Walter, M. (DESY, Zeuthen) ; Wang, J.J. (Tsinghua U., Beijing) ; Wegener, D. (Dortmund U.) ; Werthenbach, U. (Siegen U.) ; Wolters, H. (LIP, Coimbra) ; Wurth, R. (DESY) ; Wurz, A. (Mannheim U.) ; Xella-Hansen, S. (Bohr Inst.) ; Zaitsev, Yu. (Moscow, ITEP) ; Zavertyaev, M. (Lebedev Inst.) ; Zeuner, T. (Siegen U.) ; Zhelezov, A. (Moscow, ITEP) ; Zheng, Z. (Beijing, Inst. High Energy Phys.) ; Zimmermann, R. (Rostock U.) ; Zivko, T. (Stefan Inst., Ljubljana) ; Zoccoli, A. (INFN, Bologna)

Published in: Eur.Phys.J.
Year: 2009
Vol.: C60
Page No: 517-524
Pages: 9

Abstract: A study of the angular distributions of leptons from decays of J/psi's produced in p-C and p-W collisions at sqrt{s}=41.6 GeV has been performed in the Feynman-x region -0.34 < x_F < 0.14 and for transverse momentum up to 5.4 GeV/c. The data were collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The results, based on a clean selection of 2.3 x 10^5 J/psi's reconstructed in both the e^+ e^- and mu^+ mu^- decay channels, indicate that J/psi's are produced with longitudinal polarization. The magnitude of the effect is maximal at low p_T. For p_T >1 GeV/c a significant dependence on the reference frame is found: the polar anisotropy is more pronounced in the Collins-Soper frame and almost vanishes in the helicity frame, where, instead, a significant azimuthal anisotropy arises.

Web-Page: http://inspirebeta.net/record/810555/files/co_electrons.png; http://inspirebeta.net/record/810555/files/co_muons.png; http://inspirebeta.net/record/810555/files/cw_th_pt_cs.png; http://inspirebeta.net/record/810555/files/cw_th_xf_cs.png; http://inspirebeta.net/record/810555/files/ph_electrons.png; http://inspirebeta.net/record/810555/files/ph_muons.png; http://inspirebeta.net/record/810555/files/ph_pt.png; http://inspirebeta.net/record/810555/files/ph_xf.png; http://inspirebeta.net/record/810555/files/phth_electrons.png; http://inspirebeta.net/record/810555/files/phth_muons.png; http://inspirebeta.net/record/810555/files/phth_pt.png; http://inspirebeta.net/record/810555/files/phth_xf.png; http://inspirebeta.net/record/810555/files/th_pt.png; http://inspirebeta.net/record/810555/files/th_xf.png

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