Femtoscopic measurements in $p$+Pb collisions at $\sqrt{s_{_{\text{NN}}}}= 5.02$~TeV with ATLAS at the LHC

TL;DR

This paper reports femtoscopic measurements of identical pions in p+Pb collisions at 5.02 TeV with ATLAS, revealing the size and shape of the particle emission region to understand collective behavior.

Contribution

It presents the first ATLAS HBT measurements in p+Pb collisions, analyzing the spatio-temporal structure of the particle source using correlation functions.

Findings

HBT radii decrease with increasing pair momentum.

Correlation functions vary with collision centrality.

Results suggest collective expansion in p+Pb collisions.

Abstract

Recent measurements in two-particle correlations in $p$+Pb collisions suggest collective behavior reminiscent of that observed in Pb+Pb. Femtoscopic measurements may provide useful insight on this behavior because they image the spatio-temporal size of the particle emitting region. This proceeding presents identical-pion Hanbury Brown and Twiss (HBT) measurements from ATLAS using one- and three-dimensional correlation functions. Pions are identified using $\text{d}E/\text{d}x$ measured in the pixel detector. Correlation functions and the resulting HBT radii are shown as a function of pair momentum ($k_{\rm T}$) and collision centrality.