Coherent J/ ψ photoproduction in ultra-peripheral Pb–Pb collisions at √sNN=2.76 TeV

Abelev, B. and Adam, J. and Adamová, D. and Adare, A. M. and Aggarwal, M. M. and Aglieri, Rinella G. and Agnello, M. and Agócs, András and Agostinelli, A. and Aguilar, Salazar S. and Ahammed, Z. and Ahmad, Masoodi A. and Ahmad, N. and Ahn, S. A. and Ahn, S. U. and Akindinov, A. and Aleksandrov, D. and Alessandro, B. and Alfaro, Molina R. and Alici, A. and Alkin, A. and Almaráz, Aviña E. and Alme, J. and Alt, T. and Altini, V. and Altinpinar, S. and Altsybeev, I. and Andrei, C. and Andronic, A. and Anguelov, V. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Lévai, Péter and Molnár, Levente and Pochybova, Sona (2013) Coherent J/ ψ photoproduction in ultra-peripheral Pb–Pb collisions at √sNN=2.76 TeV. PHYSICS LETTERS B, 718 (4-5). pp. 1273-1283. ISSN 0370-2693

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Abstract

The ALICE collaboration has made the first measurement at the LHC of J/ ψ photoproduction in ultra-peripheral Pb-Pb-collisions at √sNN= 2.76 TeV. The J/ ψ is identified via its dimuon decay in the forward rapidity region with the muon spectrometer for events where the hadronic activity is required to be minimal. The analysis is based on an event sample corresponding to an integrated luminosity of about 55 μb−1. The cross section for coherent J/ ψ production in the rapidity interval - 3.6 < y < -2.6 is measured to be d σ coh J/ ψ /dy = 1.00 ± 0.18(stat)+0.24 −0.26(syst) mb. The result is compared to theoretical models for coherent J/ ψ production and found to be in good agreement with those models which include nuclear gluon shadowing.

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