Effects of the detector non-uniformity in pion directed flow measurement relative to the spectator plane by the NA49 experiment at the CERN SPS

Oleg Golosov,Ilya Selyuzhenkov,Evgeny Kashirin,Viktor Klochkov

doi:10.1051/epjconf/201920406011

Abstract

Results are presented for directed flow υ1 of negatively charged pions measured relative to the spectator plane in Pb+Pb collisions at the beam energy 40A GeV recorded by the NA49 experiment at CERN. The measurements were performed as a function of rapidity and transverse momentum in two classes of collision centrality. The projectile spectator symmetry plane is estimated using the transverse segmentation of the forward hadron calorimeters. Analysis details related to event selection and particle identification are provided along with a description of the procedure used to apply corrections for the limited detection efficiency. Additionally a systematic study of effects due to detector non-uniformity on pion directed flow measurement is presented.

Highlights

Results are presented for directed flow v1 of negatively charged pions measured relative to the spectator plane in Pb+Pb collisions at the beam energy 40A GeV recorded by the NA49 experiment at CERN
The NA49 experiment at the CERN SPS is the predecessor of the currently operating fixed target NA61/SHINE experiment, which has recently extended its program with a Pb-ion beam momentum scan at 13A, 30A and 150A GeV/c
The NA49 and NA61/SHINE data complement the measurement of flow harmonics available from the Beam Energy Scan (BES) program of STAR at RHIC [2] and extend the measurement towards forward rapidity up to the region where projectile spectators appear

Summary

Introduction

Results are presented for directed flow v1 of negatively charged pions measured relative to the spectator plane in Pb+Pb collisions at the beam energy 40A GeV recorded by the NA49 experiment at CERN. NA49 collected data for Pb+Pb collisions at beam energies of 20A, 30A, 40A, 80A and 158A GeV [1]. The ring calorimeter (RCAL) [4] was positioned at 18 meters from the target and its transverse granularity of 10 rings in radial and 24 modules in azimuthal direction is used to estimate the spectator plane resolution of the veto calorimeter.

Results

Conclusion