Proton hot spots and exclusive vector meson production

TL;DR

This paper investigates how gluonic hot spots within protons influence exclusive vector meson production in deep inelastic scattering, using the Color Glass Condensate framework to analyze cross sections and fluctuations.

Contribution

It introduces a model of gluonic hot spots within protons to analytically compute vector meson production cross sections, highlighting the role of fluctuations and structure at different momentum transfers.

Findings

Coherent cross section is sensitive to target size and probe structure.

Incoherent cross section is dominated by color fluctuations at small and large t.

Model reproduces t-dependence but suggests additional fluctuations are needed.

Abstract

We explore consequences of the existence of gluonic hot spots inside the proton for coherent and incoherent exclusive vector meson production cross sections in deep inelastic scattering. By working in the dilute limit of the Color Glass Condensate framework to compute the cross sections for Gaussian hot spots of fluctuating color charges and employing a non-relativistic vector meson wave function, we are able to perform large parts of the calculation analytically. We find that the coherent cross section is sensitive to both the size of the target and the structure of the probe. The incoherent cross section is dominated by color fluctuations at small transverse momentum transfer ($t$), by proton and hot spot sizes as well as the structure of the probe at medium $t$ and again by color fluctuations at large $t$. While the $t$-dependence of the cross section is well reproduced in our model, the relative normalization between the coherent and the incoherent cross sections points to the need for additional fluctuations in the proton.