Bose-Einstein Correlations in a Fluid Dynamical Scenario for Proton-Proton Scattering at 7 TeV

TL;DR

This paper models proton-proton collisions at 7 TeV using fluid dynamics to analyze pion pair correlations, reproducing experimental trends in femtoscopic radii and their dependence on pair momentum and multiplicity.

Contribution

It introduces a fluid dynamical approach to describe femtoscopic correlations in high-energy proton-proton scattering, connecting string expansion and hydrodynamical expansion regimes.

Findings

Radii decrease with pair transverse momentum, more so at higher multiplicities.

The model reproduces the experimental trend of radius reduction with increasing multiplicity.

Transition from string expansion to hydrodynamical expansion explains the observed radius behavior.

Abstract

Using a fluid dynamical scenario for $pp$ scattering at 7 TeV, we compute correlation functions for $\pi^+\pi^+$ pairs. Femtoscopic radii are extracted based on three-dimensional parametrizations of the correlation functions. We study the radii as a function of the transverse momenta of the pairs, for different multiplicity classes, corresponding to recent experimental results from ALICE. We find the same decrease of the radii with $k_T$, more and more pronounced with increasing multiplicity, but absent for the lowest multiplicities. In the model we understand this as transition from string expansion (low multiplicity) towards a three-dimensional hydrodynamical expansion (high multiplicity).