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

Research output: Book/ReportPh.D. thesis

Valentina Zaccolo

The charged–particle distribution (P(Nch) as a function of Nch), producedin high energy collisions between protons (pp) and between protons and heavynucleus (pPb), depends on the fundamental processes, which lead to the formationof the observed particles. In particular, the so–called multiplicity distributionis sensitive to the number of collisions between quarks and gluonscontained in the colliding systems.In this thesis, data using the Forward Multiplicity Detector and the SiliconPixel Detector of ALICE at CERN’s Large Hadron Collider (LHC) arepresented, for pp and pPb collisions. For the first time the multiplicity distributionsare performed over such a wide kinematic range at the LHC (pseudorapiditycoverage of ;-3:4 < η < +5:1) and at the highest energies ever,i.e. all available energies at the LHC’s first run: at 8 =0.9, 2.76, 7 and 8 TeVfor pp collisions and at  8  =5.02 TeV for pPb and Pbp collisions.The results are compared, where possible, with the results of other LHCexperiments and with theoretical Monte Carlo simulations (including PYTHIA,PHOJET and DMPJET) and with the IP–Glasma model. Moreover,data are compared using the Koba–Nielsen–Olesen (KNO) model, and it appearsthat this scaling is broken at energies from 0.9 GeV for pp collisions.Results for pPb collisions suggest that current models which include ColorGlass Condensate effects, i.e. models based on the assumption of the saturationdensity of gluons, cannot reproduce the data.
Original languageEnglish
PublisherThe Niels Bohr Institute, Faculty of Science, University of Copenhagen
Number of pages164
Publication statusPublished - 2015

ID: 142311804