Probing gluon density fluctuations at large momentum transfer $|t|$ at HERA

TL;DR

This paper models gluon density fluctuations in the proton using a hotspot framework to explain the incoherent $J/ ho$ photoproduction cross-section at large momentum transfer, matching HERA data.

Contribution

It introduces a multi-level hotspot model for gluon fluctuations that accurately describes incoherent diffraction data at high $|t|$ values.

Findings

Three-level hotspot model fits all data up to $|t|=30$ GeV$^2$

Fluctuations are significant in both saturated and non-saturated models

Model predictions agree with HERA measurements

Abstract

The information on the gluonic structure and its fluctuations is captured by the differential $|t|$ spectrum in diffractive events. The incoherent cross-section is sensitive to the fluctuations in the target wavefunction in such events. We investigate the incoherent $ep$ cross-section in $J/\psi$ photoproduction using the impact-parameter dependent dipole model. The spatial gluonic structure is modelled as hotspots of gluon density having substructure where this substructure is modelled as hotspots within hotspots. We find that three levels of the substructure provide a good description of all the data, available up to $|t|=30~$GeV$^2$. We investigate these fluctuations in both the saturated and non-saturated dipole models and compare our predictions with the HERA Data.