First Measurement of the |t | Dependence of Incoherent J/ψ Photonuclear Production

Abstract

The first measurement of the cross section for incoherent photonuclear production of J / ψ vector mesons as a function of the Mandelstam | t | variable is presented. The measurement was carried out with the ALICE detector at midrapidity, | y | 0.8 , using ultraperipheral collisions of Pb nuclei at a center-of-mass energy per nucleon pair of s NN = 5.02 TeV . This rapidity interval corresponds to a Bjorken- x range ( 0.3 – 1.4 ) × 10 − 3 . Cross sections are given in five | t | intervals in the range 0.04 | t | 1 GeV 2 and compared to the predictions by different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a | t | dependence of the cross section much steeper than in data. The inclusion of such fluctuations in the same models provides a better description of the data. © 2024 CERN, for the ALICE Collaboration 2024 CERN