https://doi.org/10.1140/epjc/s10052-009-0965-7
Regular Article - Experimental Physics
Kinematic distributions and nuclear effects of J/ψ production in 920 GeV fixed-target proton-nucleus collisions
1
NIKHEF, 1009, DB, Amsterdam, The Netherlands
2
Department ECM, Faculty of Physics, University of Barcelona, 08028, Barcelona, Spain
3
Institute for High Energy Physics, Beijing, 100039, People’s Republic of China
4
Institute of Engineering Physics, Tsinghua University, Beijing, 100084, People’s Republic of China
5
Institut für Physik, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
6
Dipartimento di Fisica dell’ Università di Bologna and INFN Sezione di Bologna, 40126, Bologna, Italy
7
Department of Physics, University of Cincinnati, Cincinnati, OH, 45221, USA
8
LIP Coimbra, 3004-516, Coimbra, Portugal
9
Niels Bohr Institutet, 2100, Copenhagen, Denmark
10
Institut für Physik, Universität Dortmund, 44221, Dortmund, Germany
11
Joint Institute for Nuclear Research Dubna, 141980, Dubna, Moscow region, Russia
12
DESY, 22603, Hamburg, Germany
13
Max-Planck-Institut für Kernphysik, 69117, Heidelberg, Germany
14
Physikalisches Institut, Universität Heidelberg, 69120, Heidelberg, Germany
15
Department of Physics, University of Houston, Houston, TX, 77204, USA
16
Institute for Nuclear Research, Ukrainian Academy of Science, 03680, Kiev, Ukraine
17
J. Stefan Institute, 1001, Ljubljana, Slovenia
18
University of Ljubljana, 1001, Ljubljana, Slovenia
19
University of California, Los Angeles, CA, 90024, USA
20
Lehrstuhl für Informatik V, Universität Mannheim, 68131, Mannheim, Germany
21
University of Maribor, 2000, Maribor, Slovenia
22
Institute of Theoretical and Experimental Physics, 117218, Moscow, Russia
23
Max-Planck-Institut für Physik, Werner-Heisenberg-Institut, 80805, München, Germany
24
Dept. of Physics, University of Oslo, 0316, Oslo, Norway
25
Fachbereich Physik, Universität Rostock, 18051, Rostock, Germany
26
Fachbereich Physik, Universität Siegen, 57068, Siegen, Germany
27
Institute for Nuclear Research, INRNE-BAS, Sofia, Bulgaria
28
Universiteit Utrecht/NIKHEF, 3584, CB, Utrecht, The Netherlands
29
DESY, 15738, Zeuthen, Germany
30
Physik-Institut, Universität Zürich, 8057, Zürich, Switzerland
* e-mail: nedden@mail.desy.de
Received:
3
December
2008
Revised:
13
February
2009
Published online:
10
March
2009
Measurements of the kinematic distributions of J/ψ mesons produced in p–C, p–Ti and p–W collisions at in the Feynman-x region −0.34<x F <0.14 and for transverse momentum up to p T =5.4 GeV/c are presented. The x F and p T dependencies of the nuclear suppression parameter, α, are also given. The results are based on 2.4×105 J/ψ mesons reconstructed in both the e + e − and μ + μ − decay channels. The data have been collected by the HERA-B experiment at the HERA proton ring of the DESY laboratory. The measurement explores the negative region of x F for the first time. The average value of α in the measured x F region is 0.981±0.015. The data suggest that the strong nuclear suppression of J/ψ production previously observed at high x F turns into an enhancement at negative x F .
© Springer-Verlag, 2009