Pseudorapidity dependence of multiplicity and transverse momentum fluctuations in pp collisions at SPS energies

TL;DR

This study investigates how multiplicity and transverse momentum fluctuations in proton-proton collisions vary with pseudorapidity and energy, revealing charge and pseudorapidity dependence, and comparing results with the EPOS model.

Contribution

It provides the first detailed analysis of pseudorapidity dependence of fluctuations in pp collisions across multiple energies, using strongly intensive measures and comparing with theoretical models.

Findings

Fluctuations depend on hadron charge and pseudorapidity interval.

EPOS model fails to describe certain fluctuation measures.

Results show energy and pseudorapidity influence on fluctuation behavior.

Abstract

A search for the critical behavior of strongly interacting matter was performed at the NA61/SHINE experiment by studying event-by-event fluctuations of multiplicity and transverse momentum of charged hadrons produced in inelastic p+p collisions at 20, 31, 40, 80 and 158 GeV/c beam momentum. Results for the energy dependence of the scaled variance of the multiplicity distribution and for two families of strongly intensive measures of multiplicity and transverse momentum fluctuations $\Delta[P_{T},N]$ and $\Sigma[P_{T},N]$ are presented. These quantities were studied in different pseudorapidity intervals, which correspond to changing the baryon chemical potential and the temperature at the freeze-out stage. The strongly intensive measures $\Delta[N_{F},N_{B}]$ and $\Sigma[N_{F},N_{B}]$ were also used in the analysis of short- and long-range multiplicity correlations. Results on multiplicity and transverse momentum fluctuations significantly depend on the charges of the selected hadrons and the width and/or location of pseudorapidity intervals. The event generator EPOS does not describe the data for the $\Delta[P_{T},N]$ measure, but provides a fair description of $\Sigma[P_{T},N]$. The measure $\Sigma[N_{F},N_{B}]$ of forward-backward fluctuations is reproduced reasonably well by the EPOS model.