In:
Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2023, No. 10 ( 2023-10-20)
Abstract:
The cross section for coherent photonuclear production of J/ ψ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of $$ \sqrt{{\textrm{s}}_{\textrm{NN}}} $$ s NN = 5.02 TeV. Cross sections are presented in five different J/ ψ rapidity ranges within | y | 〈 4, with the J/ ψ reconstructed via its dilepton decay channels. In some events the J/ ψ is not accompanied by EMD, while other events do produce neutrons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range 17 〈 W γ Pb , n 〈 920 GeV, where W γ Pb , n is the centre-of-mass energy per nucleon of the γ Pb system. This range corresponds to a Bjorken- x interval spanning about three orders of magnitude: 1.1 × 10 − 5 〈 x 〈 3.3 × 10 − 2 . In addition to the ultra-peripheral and photonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energies.
Type of Medium:
Online Resource
ISSN:
1029-8479
DOI:
10.1007/JHEP10(2023)119
Language:
English
Publisher:
Springer Science and Business Media LLC
Publication Date:
2023
detail.hit.zdb_id:
2027350-2
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