Coherent J/ ψ Photoproduction in Ultra-Peripheral PbPb Collisions at √s[subscript NN = 2.76 TeV with the CMS Experiment
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Author(s)
CMS Collaboration
Apyan, Aram
Barbieri, Richard Alexander
Baty, Austin Alan
Bi, Ran
Bierwagen, Katharina
Brandt, Stephanie Akemi
Busza, Wit
Cali, Ivan Amos
Demiragli, Zeynep
Date Issued
July 2017
Journal
Physics Letters B
Publisher
Elsevier BV
Citation
Khachatryan, V. et al. “Coherent J/ ψ Photoproduction in Ultra-Peripheral PbPb Collisions at √s[subscript NN = 2.76 TeV with the CMS Experiment.” Physics Letters B 772 (September 2017): 489–511 © 2017 The Author(s)
Version
Final published version
Abstract
The cross section for coherent J/ψ photoproduction accompanied by at least one neutron on one side of the interaction point and no neutron activity on the other side, X[subscript n]0[subscript n], is measured with the CMS experiment in ultra-peripheral PbPb collisions at √s[subscript NN = 2.76 TeV. The analysis is based on a data sample corresponding to an integrated luminosity of 159μb ⁻¹, collected during the 2011 PbPb run. The J/ψ mesons are reconstructed in the dimuon decay channel, while neutrons are detected using zero degree calorimeters. The measured cross section is dσ [subscript Xn0n][superscript coh] /dy(J/ψ)=0.36±0.04(stat)±0.04(syst) mb in the rapidity interval 1.8 < |y| < 2.3. Using a model for the relative rate of coherent photoproduction processes, this X n 0 n measurement gives a total coherent photoproduction cross section of dσ[superscript coh] /dy(J/ψ)=1.82±0.22(stat)±0.20(syst)±0.19(theo) mb. The data strongly disfavor the impulse approximation model prediction, indicating that nuclear effects are needed to describe coherent J/ψ photoproduction in γ+Pb interactions. The data are found to be consistent with the leading twist approximation, which includes nuclear gluon shadowing.
MIT Department
Massachusetts Institute of Technology. Department of Physics
Massachusetts Institute of Technology. Laboratory for Nuclear Science
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Creative Commons Attribution 4.0 International License
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DOI of Published Version
https://doi.org/10.1016/J.PHYSLETB.2017.07.001
