System-size dependence of the charged-particle pseudorapidity density at [formula omitted] with ALICE

Christian Holm Christensen

doi:10.1016/j.nuclphysa.2017.05.066

Abstract

We present the charged-particle pseudorapidity density in pp, p–Pb, and Pb–Pb collisions at sNN=5.02 TeV over a broad pseudorapidity range. The distributions are determined using the same experimental apparatus and methodologies, thereby minimizing systematic uncertainties, and providing clear and model-independent observations on the system-size dependence of the particle production at relativistic energies. An increase of particle production in Pb–Pb collisions near mid-rapidity, relative to pp collisions, is observed. The relative linearity in p–Pb collisions of the ratio to the smaller system indicate a coherent particle production throughout the longitudinal extend of the collision zone.

Highlights

With thePb–Pb and pp collisions provided by the Large HadronCollider at a collision energy of5.02 TeV in 2015, and the p–Pb collisions provided in 2013, it is for the first time possible to compare the 3 collisions systems at the same ultrarelativistic energies
pp collisions provided by the Hadron
we can learn about the production mechanisms

Summary

Introduction

5.02 TeV in 2015, and the p–Pb collisions provided in 2013, it is for the first time possible to compare the 3 collisions systems at the same ultrarelativistic energies In this proceeding, we compare the primary charged-particle pseudorapidity density (dNch/dη) of all three collision systems over a wide pseudorapidity (η) range of −3.5 < η < 5 using data from ALICE. The minimum bias trigger for p–Pb and Pb–Pb collisions in ALICE is defined as a coincidence between the A (z > 0) and C (z < 0) sides of the V0 detector. In the forward regions (−3.5 < η < −1.8 and 1.8 < η < 5), the measurement is provided by the analysis of the deposited energy signal in the FMD: a statistical approach to calculate the inclusive number of charged particles; and a data-driven correction — derived from previous satellite–main collisions — to remove the large background from secondary particles. For p–Pb collisions, the systematic uncertainty due to the centrality classification amounts to 1.5% and 2% in centrality ranges (0 − 40)% and (40 − 100)%, respectively [7]

Results

ALICE Preliminary

Summary