Global Conservation Laws and Femtoscopy of Small Systems

TL;DR

This paper develops a formalism to account for global conservation laws affecting two-pion correlations in small collision systems, aiding the comparison with heavy ion collision femtoscopic measurements.

Contribution

It introduces a new method to calculate and correct for N-body correlations caused by conservation laws in low-multiplicity collisions.

Findings

The formalism effectively isolates femtoscopic correlations from conservation law effects.

Application to p+p and d+A collisions improves interpretation of two-pion correlation data.

Insights into non-identical particle correlations and femtoscopic asymmetries are provided.

Abstract

It is important to understand, in detail, two-pion correlations measured in p+p and d+A collisions. In particular, one wishes to understand the femtoscopic correlations, in order to compare to similar measurements in heavy ion collisions. However, in the low-multiplicity final states of these systems, global conservation laws generate significant N-body correlations which project onto the two-pion space in non-trivial ways and complicate the femtoscopic analysis. We discuss a formalism to calculate and account for these correlations in collisions dominated by a single particle species (e.g. pions). We also discuss effects on two-particle correlations between non-identical particles, the understanding of which may be important in the study of femtoscopic space-time asymmetries.