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

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.