Relating Charged Particle Multiplicity to Impact Parameter in Heavy-Ion Collisions at NICA Energies

Petr Parfenov,Dim Idrisov,Vinh Ba Luong,Arkadiy Taranenko

doi:10.3390/particles4020024

Abstract

The size and evolution of the matter created in relativistic heavy-ion collisions strongly depend on collision geometry, defined by the impact parameter. However, the impact parameter cannot be measured directly in an experiment but might be inferred from final state observables using the centrality procedure. We present the procedure of centrality determination for the Multi-Purpose Detector (MPD) at the NICA collider and its performance using the multiplicity of produced charged particles at midrapidity. The validity of the procedure is assessed using the simulated data for Au + Au collisions at sNN = 4–11 GeV.

Highlights

One of the main purposes of the upcoming Multi-Purpose Detector (MPD) at the Nuclotron based Ion Collider fAcility (NICA) is to study the properties of the strongly interacting matter created in relativistic heavy-ion collisions [1]
Experimental heavy-ion collisions can be characterized by the measured particle multiplicities Nch around midrapidity or by the energy Esp measured in the forward rapidity region, which is sensitive to the spectator fragments
We present the procedure of centrality determination for the MultiPurpose Detector at NICA and its performance using the multiplicity of produced charged particles at midrapidity

Summary

Introduction

One of the main purposes of the upcoming Multi-Purpose Detector (MPD) at the Nuclotron based Ion Collider fAcility (NICA) is to study the properties of the strongly interacting matter created in relativistic heavy-ion collisions [1]. The measured dN/dNch (dE/dEsp ) distribution is divided into percentile centrality classes, with the most central class defined by X% of events with the highest value of Nch (smallest forward energy Esp ), which corresponds to small values of the impact parameter b. This is referred to as 0–X% centrality. The Γ-fit method is based on the assumption that the relation between the measured Nch and b is purely probabilistic and can be inferred from data without relying on any specific model of collisions.

Impact Parameter Estimation from the Multiplicity of Charged Particles

Centrality Determination Using MC-Glauber Approach

Centrality Determination Using the Γ-Fit Method

Results

Conclusions