Hanbury-Brown-Twiss measurements at large rapidity separations, or can we measure the proton radius in p-A collisions?

TL;DR

This paper discusses how Hanbury-Brown-Twiss correlations in p-A collisions can reveal the gluonic size of the proton, offering a novel method to measure the proton radius through two-particle correlations at large rapidity separations.

Contribution

It highlights the presence of HBT correlations at large rapidity separations in p-A collisions and proposes using this effect to measure the proton's gluonic size directly.

Findings

HBT correlations are present at large rapidity separations.

These correlations reflect the gluonic size of the proton.

Potential to measure proton radius via HBT in p-A collisions.

Abstract

We point out that current calculations of inclusive two-particle correlations in p-A collisions based on the Color Glass Condensate approach exhibit a contribution from Hanbury-Brown-Twiss correlations. These HBT correlations are quite distinct from the standard ones, in that they are apparent for particles widely separated in rapidity. The transverse size of the emitter which is reflected in these correlations is the gluonic size of the proton. This raises an interesting possibility of measuring the proton size directly by the HBT effect of particle pairs produced in p-A collisions.