Measurement of an Excess in the Yield of <i>J</i>/ψ at Very Low <i>p<sub>T</sub></i> in Pb-Pb Collisions at √<i>s<sub>NN</sub></i>=2.76 TeV



Adam, J, Adamova, D, Aggarwal, MM, Rinella, G Aglieri, Agnello, M, Agrawal, N, Ahammed, Z, Ahn, SU, Aiola, S, Akindinov, A
et al (show 972 more authors) (2016) Measurement of an Excess in the Yield of <i>J</i>/ψ at Very Low <i>p<sub>T</sub></i> in Pb-Pb Collisions at √<i>s<sub>NN</sub></i>=2.76 TeV. PHYSICAL REVIEW LETTERS, 116 (22). 222301-.

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Abstract

We report on the first measurement of an excess in the yield of J/ψ at very low transverse momentum (p_{T}<0.3  GeV/c) in peripheral hadronic Pb-Pb collisions at sqrt[s_{NN}]=2.76  TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/ψ in the rapidity range 2.5<y<4 reaches about 7 (2) in the p_{T} range 0-0.3  GeV/c in the 70%-90% (50%-70%) centrality class. The J/ψ production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/ψ is the underlying physics mechanism. If confirmed, the observation of J/ψ coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuclear radius opens new theoretical and experimental challenges and opportunities. In particular, coherent photoproduction accompanying hadronic collisions may provide insight into the dynamics of photoproduction and nuclear reactions, as well as become a novel probe of the quark-gluon plasma.

Item Type: Article
Uncontrolled Keywords: ALICE Collaboration
Depositing User: Symplectic Admin
Date Deposited: 13 Jul 2016 11:22
Last Modified: 05 Oct 2023 11:19
DOI: 10.1103/PhysRevLett.116.222301
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3002287

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