# Quark Matter 2017

5-11 February 2017
Hyatt Regency Chicago
America/Chicago timezone

## System-size dependence of the charged-particle pseudorapidity density distribution at 5.02 TeV with ALICE

7 Feb 2017, 12:00
20m
Regency A

### Regency A

Oral Initial State Physics and Approach to Equilibrium

### Speaker

Christian Holm Christensen (University of Copenhagen (DK))

### Description

The dependence of particle production on the size of the colliding system (pp, p-Pb, and Pb-Pb) is studied using the most recent measurements at $\sqrt{s_{\rm{NN}}}=5.02~\rm{TeV}$ from ALICE for -3.4 < η < +5.0 employing the same methodology for the three colliding systems. Comparing particle production between Pb-Pb and p-Pb collisions to pp collisions as a reference over a wide pseudorapidity range provides insight into the longitudinal (and low-x) nature of the hot and dense medium created in heavy-ion collisions.

Studies from pp collisions at various energies show that the width of the charged-particle pseudorapidity density distribution increases with increasing collision energy. This underlines the importance of investigating the system size dependence of the particle production at the same collision energy. The approximate linearity versus η that is found in the ratio of the pseudorapidity density distributions of the different systems indicates a coherent particle production throughout the longitudinal extent of the collision region, while the dependence on pseudorapidity may reflect underlying mechanisms, for example colour fluctuations or Colour-Glass Condensate initial conditions.

Preferred Track Initial State Physics and Approach to Equilibrium ALICE

### Primary author

Christian Holm Christensen (University of Copenhagen (DK))

### Presentation materials

 1: Presentation (4:3) 2: Presentation (16:10)