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PHYSICAL REVIEW LETTERS 132, 162302 (2024)
The first experimental measurement of the incoherent photonuclear production of J/Ο in ultraperipheral heavy-ion collisions is better explained by the presence of subnuclear quantum fluctuations of the gluon field.
The first measurement of the cross-section for incoherent photonuclear production of π½/π vector mesons as a function of the Mandelstam |π‘| variable is presented. The measurement was carried out with the ALICE detector at midrapidity, |π¦|<0.8, using ultraperipheral collisions of Pb nuclei at a center-of-mass energy per nucleon pair of sqrt(π NN)=5.02ββTeV. This rapidity interval corresponds to a Bjorken-π₯ range (0.3β1.4)Γ10β3. Cross sections are given in five |π‘| intervals in the range 0.04<|π‘|<1ββGeV2 and compared to the predictions by different models. Models that ignore quantum fluctuations of the gluon density in the colliding hadron predict a |π‘| 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.
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