Measurement of event-by-event transverse momentum and multiplicity fluctuations using strongly intensive measures

Abstract

Results from the NA49 experiment at the CERN Super Proton Synchrotron (SPS) are presented on event-by-event transverse momentum and multiplicity fluctuations of charged particles, produced at forward rapidities in central Pb + Pb interactions at beam momenta 20A, 30A, 40A, 80A, and 158A GeV/c, as well as in systems of different sizes (p+p, C + C, Si + Si, and Pb + Pb) at 158A GeV/c. This publication extends the previous NA49 measurements of the strongly intensive measure ΦpT by a study of the recently proposed strongly intensive measures of fluctuations Δ[PT,N] and Σ[PT,N]. In the explored kinematic region transverse momentum and multiplicity fluctuations show no significant energy dependence in the SPS energy range. However, a remarkable system size dependence is observed for both Δ[PT,N] and Σ[PT,N], with the largest values measured in peripheral Pb + Pb interactions. The results are compared with NA61/SHINE (SPS Heavy Ion and Neutrino Experiment) measurements in p+p collisions, as well as with predictions of The Ultrarelativistic Quantum Molecular Dynamics and EPOS models.