Coherent J/ψ photoproduction in ultra-peripheral PbPb collisions at sNN=2.76TeV with the CMS experiment
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, Xn0n, is measured with the CMS experiment in ultra-peripheral PbPb collisions at √sN N = 2.76 TeV. The analysis is based on a data...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English English |
| Published: |
Elsevier
2017
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/63006/ http://irep.iium.edu.my/63006/ http://irep.iium.edu.my/63006/ http://irep.iium.edu.my/63006/3/63006_Coherent%20photoproduction%20in%20ultra-peripheral%20PbPb%20collisions%20_article.htm http://irep.iium.edu.my/63006/2/63006_Coherent%20photoproduction%20in%20ultra-peripheral%20PbPb%20collisions%20_scopus.pdf |
| Summary: | 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, Xn0n, is measured with the
CMS experiment in ultra-peripheral PbPb collisions at √sN N = 2.76 TeV. The analysis is based on a
data sample corresponding to an integrated luminosity of 159 μb−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 dσcoh
Xn0n /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 Xn0n measurement gives a total coherent photoproduction cross section
of dσcoh/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. |
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