Strong and Electromagnetic Collective Effects from NA61/SHINE

Abstract

This contribution presents new NA61/SHINE results on collective effects, including spectator-induced electromagnetic (EM) phenomena in charged pion emission in collisions at beam momentum of 150A GeV/c as well as directed flow for protons and charged pions as a function of transverse momentum and centrality in Pb+Pb collisions at 30A GeV/c. EM effects bring new, independent information on the space-time properties of the system. They may also suggest presence of the fast-moving participant charge close to the spectator system, as well as relatively fast spectator decay. The results on the directed flow at CERN SPS energies are complementary to STAR results and provide a bridge to FAIR and NICA energies. A specific picture of the longitudinal evolution of the system at CERN SPS energies emerges, where the centrality dependence of pion rapidity spectra is governed predominantly by the simple energy-momentum conservation and the collision geometry.

Overview of Results from NA61/SHINE: Uncovering Critical Structures

“…Sections 2.1-2.3 outlined the main results of the strong interaction programme in terms of bulk phenomena occurring in the central kinematic region of the reaction. Complementary studies, aimed at investigating the longitudinal evolution of the system by measuring electromagnetic (EM) effects, particle spectra and collective flow phenomena, are also described in these proceedings [27]. Measurements planned in the nearest future will be addressed below.…”

“…This section will focus only on item (1). For item (2), the reader is asked to refer to another paper in these proceedings [27], as well as to Ref. [4].…”