Quark Matter 2015 - XXV International Conference on Ultrarelativistic Nucleus-Nucleus Collisions

Charged-Particle Multiplicity Distributions over Wide Pseudorapidity Range in Proton-Proton Collisions with ALICE

28 Sept 2015, 14:50

20m

Convention room 1

Contributed talk Initial State Physics and Approach to Equilibrium Initial State Physics and Approach to Equilibrium I

Speaker

Valentina Zaccolo (University of Copenhagen (DK))

Description

The distribution of charged particles produced in high energy pp collisions, $P(N_{ch})$, as a function of $N_{ch}$, is sensitive to the number of collisions between quarks and gluons contained in the colliding systems and to the mechanisms underlying particle production. In particular, it is a good probe for the saturation density of gluons in the colliding hadrons. For the first time, the multiplicity distributions for pp collisions are measured over a wide kinematic range at the LHC (pseudorapidity coverage of $-3.4<\eta <+5.1$). The $P(N_{ch})$ are obtained at LHC Run 1 energies: from $\sqrt{s}=$0.9 to 8 TeV, and at the highest available energy $\sqrt{s}=$13 TeV from Run 2. The distributions are measured using the Forward Multiplicity Detector (FMD) and the Silicon Pixel Detector (SPD) of ALICE at LHC. The results are compared, where possible, with the results of other LHC experiments and with Monte Carlo simulations. Moreover, data are compared using the Koba--Nielsen--Olesen (KNO) model, where it appears that the scaling predicted by this model is broken at energies from 0.9 TeV.

Presentation materials

QuarkMatter2015_Zaccolo.pdf