The first measurement of the cross section for coherent J/ψ photoproduction as a function of |t|, the square of the momentum transferred between the incoming and outgoing target nucleus, is presented. The data were measured with the ALICE detector in ultra-peripheral Pb–Pb collisions at a centre-of-mass energy per nucleon pair √sNN = 5.02 TeV with the J/ψ produced in the central rapidity region |y| < 0.8, which corresponds to the small Bjorken-x range (0.3 − 1.4) × 10 The measured |t|-dependence is not described by computations based only on the Pb nuclear form factor, while the photonuclear cross section is better reproduced by models including shadowing according to the leading-twist approximation, or gluon-saturation effects from the impact-parameter dependent Balitsky–Kovchegov equation. These new results are therefore a valid tool to constrain the relevant model parameters and to investigate the transverse gluonic structure at very low Bjorken-x.

First measurement of the |t|-dependence of coherent J/ψ photonuclear production

Beole, S.;Bianchi, L.;Botta, E.;Ferretti, A.;Gagliardi, M.;Masera, M.;Mazzaschi, F.;Puccio, M.;Trogolo, S.;Vercellin, E.;
2021-01-01

Abstract

The first measurement of the cross section for coherent J/ψ photoproduction as a function of |t|, the square of the momentum transferred between the incoming and outgoing target nucleus, is presented. The data were measured with the ALICE detector in ultra-peripheral Pb–Pb collisions at a centre-of-mass energy per nucleon pair √sNN = 5.02 TeV with the J/ψ produced in the central rapidity region |y| < 0.8, which corresponds to the small Bjorken-x range (0.3 − 1.4) × 10 The measured |t|-dependence is not described by computations based only on the Pb nuclear form factor, while the photonuclear cross section is better reproduced by models including shadowing according to the leading-twist approximation, or gluon-saturation effects from the impact-parameter dependent Balitsky–Kovchegov equation. These new results are therefore a valid tool to constrain the relevant model parameters and to investigate the transverse gluonic structure at very low Bjorken-x.
2021
817
136280
136280
photonuclear production, J/Psi, Pb-Pb collisions
Acharya, S.; Adamová, D.; Adler, A.; Adolfsson, J.; Aglieri Rinella, G.; Agnello, M.; Agrawal, N.; Ahammed, Z.; Ahmad, S.; Ahn, S.U.; Akbar, Z.; Akind...espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/1789437
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