TY - JOUR
T1 - First measurement of coherent ρ0 photoproduction in ultra-peripheral Xe–Xe collisions at sNN=5.44 TeV
AU - ALICE Collaboration
AU - Acharya, S.
AU - Adamová, D.
AU - Adler, A.
AU - Adolfsson, J.
AU - Aglieri Rinella, G.
AU - Agnello, M.
AU - Agrawal, N.
AU - Ahammed, Z.
AU - Ahmad, S.
AU - Ahn, S. U.
AU - Akbar, Z.
AU - Akindinov, A.
AU - Al-Turany, M.
AU - Albuquerque, D. S.D.
AU - Aleksandrov, D.
AU - Alessandro, B.
AU - Alfanda, H. M.
AU - Alfaro Molina, R.
AU - Ali, B.
AU - Ali, Y.
AU - Alici, A.
AU - Alizadehvandchali, N.
AU - Alkin, A.
AU - Alme, J.
AU - Alt, T.
AU - Altenkamper, L.
AU - Altsybeev, I.
AU - Anaam, M. N.
AU - Andrei, C.
AU - Andreou, D.
AU - Andronic, A.
AU - Anguelov, V.
AU - Antičić, T.
AU - Antinori, F.
AU - Antonioli, P.
AU - Anuj, C.
AU - Apadula, N.
AU - Aphecetche, L.
AU - Appelshäuser, H.
AU - Arcelli, S.
AU - Arnaldi, R.
AU - Arratia, M.
AU - Arsene, I. C.
AU - Arslandok, M.
AU - Augustinus, A.
AU - Averbeck, R.
AU - Aziz, S.
AU - Azmi, M. D.
AU - Bazo Alba, J. L.
AU - Gago, A. M.
N1 - Publisher Copyright:
© 2021 European Organization for Nuclear Research
PY - 2021/9/10
Y1 - 2021/9/10
N2 - 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.)−16.9+17.5(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.
AB - 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.)−16.9+17.5(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.
UR - http://www.scopus.com/inward/record.url?scp=85111237259&partnerID=8YFLogxK
U2 - 10.1016/j.physletb.2021.136481
DO - 10.1016/j.physletb.2021.136481
M3 - Article
AN - SCOPUS:85111237259
SN - 0370-2693
VL - 820
JO - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
JF - Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
M1 - 136481
ER -