Identity Method for Particle Number Fluctuations and Correlations

TL;DR

This paper extends the identity method to accurately measure all second moments of particle number fluctuations across multiple hadron species, effectively removing misidentification effects in nucleus-nucleus collision experiments.

Contribution

The paper generalizes the identity method to handle multiple hadron species and introduces linear combinations of moments that can be experimentally determined.

Findings

Complete elimination of misidentification effects in fluctuation measurements.

Extension of the identity method to multiple hadron species.

Reduction of the problem to solving linear equations for moments.

Abstract

An incomplete particle identification distorts the observed event-by-event fluctuations of the hadron chemical composition in nucleus-nucleus collisions. A new experimental technique called the {\em identity method} was recently proposed. It eliminated the misidentification problem for one specific combination of the second moments in a system of two hadron species. In the present paper this method is extended to calculate all the second moments in a system with arbitrary number of hadron species. Special linear combinations of the second moments are introduced. These combinations are presented in terms of single-particle variables and can be found experimentally from the event-by-event averaging. The mathematical problem is then reduced to solving a system of linear equations. The effect of incomplete particle identification is fully eliminated from the final results.