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Physics Letters B 706 (2012) 263-267
J/psi production in proton-nucleus collisions at 158 and 400 GeV
R. Arnaldi, K. Banicz, J. Castor1, B. Chaurand2, W. M. Chen, C. Cicalo, A. Colla, P. Cortese, S. Damjanovic, A. David, A. De Falco, A. Devaux1, L. Ducroux3, H. En'yo, J. Fargeix1, A. Ferretti, M. Floris, A. Foerster, P. Force1, N. Guettet1, A. Guichard3, H. Gulkanian, J. M. Heuser, M. Keil, Z. Li, C. Lourenco, J. Lozano, F. Manso1, P. Martins, A. Masoni, A. Neves, H. Ohnishi, C. Oppedisano, P. Parracho, P. Pillot3, T. Poghosyan, G. Puddu, E. Radermacher, P. Ramalhete, P. Rosinsky, E. Scomparin, J. Seixas, S. Serci, R. Shahoyan, P. Sonderegger, H. J. Specht, R. Tieulent3, A. Uras, G. Usai, R. Veenhof, H. K. Woehri
NA60 Collaboration(s)

The NA60 experiment has studied J/psi production in p-A collisions at 158 and 400 GeV, at the CERN SPS. Nuclear effects on the J/psi yield have been estimated from the A-dependence of the production cross section ratios sigma_{J/psi}^{A}/sigma_{J/psi}^{Be} (A=Al, Cu, In, W, Pb, U). We observe a significant nuclear suppression of the J/psi yield per N-N collision, with a larger effect at lower incident energy, and we compare this result with previous observations by fixed-target experiments. By studying, at the two energies, the dependence of nuclear effects on x_2, the fraction of nucleon momentum carried by the interacting parton from the target nucleus, we conclude that a combination of nuclear shadowing and break-up by target nucleons cannot be the only source of nuclear suppression of the J/psi.
1 :  LPC - Laboratoire de Physique Corpusculaire [Clermont-Ferrand]
2 :  LLR - Laboratoire Leprince-Ringuet
3 :  IPNL - Institut de Physique Nucléaire de Lyon
Physique/Physique Nucléaire Expérimentale
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