Exclusive J/ψ Photoproduction off Protons in Ultraperipheral p-Pb Collisions √sNN = 5.02 TeV

Abelev, B. and Planinić, Mirko and Poljak, Nikola and Simatović, Goran and Zyzak, M. (ALICE Collaboration) (2014) Exclusive J/ψ Photoproduction off Protons in Ultraperipheral p-Pb Collisions √sNN = 5.02 TeV. Physical Review Letters, 113 (23). pp. 232504-11. ISSN 0031-9007

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Abstract

We present the first measurement at the LHC of exclusive J/ψ photoproduction off protons, in ultraperipheral proton-lead collisions at √sNN = 5.02 TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame, 2.5 <y< 4 (p-Pb) or −3.6 <y< −2.6 (Pb-p), and no other particles observed in the ALICE acceptance. The measured cross sections σ(γ + p → J/ψ + p) are 33.2 ± 2.2 (stat) ± 3.2 (syst) ± 0.7 (theor) nb in p-Pb and 284 ± 36 (stat) ± 27 32 (syst) 26 (theor) nb in Pb-p collisions. We measure this process up to about 700 GeV in the γp center of mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the J/ψ photoproduction cross section in γp energies from about 20 to 700 GeV, or equivalently, from Bjorken x scaling variable between ~2 × 10^−2 and ~2 × 10^−5, thus indicating no significant change in the gluon density behavior of the proton between HERA and LHC energies.

Item Type: Article
Date: December 2014
Subjects: NATURAL SCIENCES > Physics
Additional Information: Copyright (2014) by the American Physical Society.
Divisions: Faculty of Science > Department of Physics
Publisher: American Physical Society
Depositing User: Gordana Stubičan Ladešić
Date Deposited: 02 Feb 2015 11:51
Last Modified: 02 Feb 2015 11:51
URI: http://digre.pmf.unizg.hr/id/eprint/3638

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