dc.contributor.author KARASU UYSAL, Ayben dc.contributor.author ALICE Collaboration dc.date.accessioned 2022-03-05T13:26:38Z dc.date.available 2022-03-05T13:26:38Z dc.date.issued 2021 dc.identifier.uri http://hdl.handle.net/20.500.12498/5386 dc.description.abstract The first measurement of the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Xe-Xe collisions at sNN‾‾‾‾√=5.44 TeV is presented. This result, together with previous HERA γp data and γ-Pb measurements from ALICE, describes the atomic number (A) dependence of this process, which is particularly sensitive to nuclear shadowing effects and to the approach to the black-disc limit of QCD at a semi-hard scale. The cross section of the Xe+Xe→ρ0+Xe+Xe process, measured at midrapidity through the decay channel ρ0→π+π−, is found to be dσ/dy=131.5±5.6(stat.)+17.5−16.9(syst.) mb. The ratio of the continuum to resonant contributions for the production of pion pairs is also measured. In addition, the fraction of events accompanied by electromagnetic dissociation of either one or both colliding nuclei is reported. The dependence on A of cross section for the coherent ρ0 photoproduction at a centre-of-mass energy per nucleon of the γA system of WγA,n=65 GeV is found to be consistent with a power-law behaviour σ(γA→ρ0A)∝Aα with a slope α=0.96±0.02(syst.). This slope signals important shadowing effects, but it is still far from the behaviour expected in the black-disc limit. en_US dc.title First measurement of coherent ρ0 photoproduction in ultra-peripheral Xe–Xe collisions at √sNN = 5.44 TeV en_US
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