Coherent J/ ψ Photoproduction in Ultra-Peripheral PbPb Collisions at √s[subscript NN = 2.76 TeV with the CMS Experiment
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; Di Matteo, Leonardo; Gomez-Ceballos, Guillelmo; Goncharov, Maxim; Gulhan, Doga Can; Iiyama, Yutaro; Innocenti, Gian Michele; Klute, Markus; Kovalskyi, Dmytro; Krajczar, Krisztian F.; Lai, Yue Shi; Lee, Yen-Jie; Levin, Andrew Michael; Luckey Jr, P David; Marini, Andrea Carlo; McGinn, Christopher Francis; Mironov, Camelia Maria; Narayanan, Siddharth Madhavan; Niu, Xinmei; Paus, Christoph M. E.; Roland, Christof E; Roland, Gunther M; Salfeld-Nebgen, Jakob Maxillian Henry; Stephans, George S. F.; Sumorok, Konstanty C; Tatar, Kaya; Varma, Mukund Madhav; Velicanu, Dragos Alexandru; Veverka, Jan; Wang, Jing; Wang, Ta-Wei; Wyslouch, Boleslaw; Yang, Ming; Wyslouch, Victoria; ... Show more Show less
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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.
Date issued
2017-07Department
Massachusetts Institute of Technology. Department of Physics; Massachusetts Institute of Technology. Laboratory for Nuclear ScienceJournal
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
ISSN
0370-2693