Energy dependence of dissociative $\mathrm{J/}\psi$ photoproduction as a signature of gluon saturation at the LHC

TL;DR

This paper presents a model linking proton structure fluctuations to gluon saturation, successfully reproducing experimental data and predicting a characteristic energy-dependent behavior of dissociative J/ψ photoproduction as a signature of gluon saturation at the LHC.

Contribution

The paper introduces a fluctuation model of proton structure with hot spots that grow with decreasing Bjorken-x, providing new insights into gluon saturation signatures at high energies.

Findings

Model reproduces HERA and LHC data on J/ψ photoproduction

Predicts a peak and decline in dissociative J/ψ cross section at high energies

Provides a potential experimental signature of gluon saturation

Abstract

We have developed a model in which the quantum fluctuations of the proton structure are characterised by hot spots, whose number grows with decreasing Bjorken-$x$. Our model reproduces the $F_2(x,Q^2)$ data from HERA at the relevant scale, as well as the exclusive and dissociative $\mathrm{J/}\psi$ photoproduction data from H1 and ALICE. Our model predicts that for $W_{\gamma\mathrm{p}} \approx 500$ GeV, the dissociative $\mathrm{J/}\psi$ cross section reaches a maximum and then decreases steeply with energy, which is in qualitatively good agreement to a recent observation that the dissociative $\mathrm{J/}\psi$ background in the exclusive $\mathrm{J/}\psi$ sample measured in photoproduction by ALICE decreases as energy increases. Our prediction provides a clear signature for gluon saturation at LHC energies.