Suppression of ψ(2S) production in p-Pb collisions at √sNN = 5.02 TeV

Abelev, B. and Adam, J. and Adamová, D. and Aggarwal, M. M. and Agnello, M. and Agostinelli, A. and Agrawal, N. and Ahammed, Z. and Ahmad, N. and Ahmed, I. and Ahn, S. U. and Ahn, S. A. and Aimo, I. and Aiola, S. and Ajaz, M. and Akindinov, A. and Alam, S. N. and Aleksandrov, D. and Alessandro, B. and Alexandre, D. and Alici, A. and Alkin, A. and Alme, J. and Alt, T. and Altinpinar, S. and Altsybeev, I. and Alves, Garcia Prado C. 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 Kiss, Gábor and Varga-Kőfaragó, Mónika and Lévai, Péter and Molnár, Levente and Oláh, László and Pochybova, Sona (2014) Suppression of ψ(2S) production in p-Pb collisions at √sNN = 5.02 TeV. JOURNAL OF HIGH ENERGY PHYSICS (12). ISSN 1126-6708

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Abstract

The ALICE Collaboration has studied the inclusive production of the charmonium state ψ(2S) in proton-lead (p-Pb) collisions at the nucleon-nucleon centre of mass energy √sNN = 5.02 TeV at the CERN LHC. The measurement was performed at forward (2.03 < ycms < 3.53) and backward (−4.46 < ycms < −2.96) centre of mass rapidities, studying the decays into muon pairs. In this paper, we present the inclusive production cross sections σψ(2S), both integrated and as a function of the transverse momentum pT, for the two ycms domains. The results are compared to those obtained for the 1S vector state (J/ ψ), by showing the ratios between the production cross sections, as well as the double ratios [ σψ(2S)/ σJ/ ψ ]pPb/[ σψ(2S)/ σJ/ ψ ]pp between p-Pb and proton-proton collisions. Finally, the nuclear modification factor for inclusive ψ(2S) is evaluated and compared to the measurement of the same quantity for J/ ψ and to theoretical models including parton shadowing and coherent energy loss mechanisms. The results show a significantly larger suppression of the ψ(2S) compared to that measured for J/ ψ and to models. These observations represent a clear indication for sizeable final state effects on ψ(2S) production.

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