2012/05/31 by B. I. Abelev, ALICE Collaboration, J. Adam +97
Mathematics · Physics and Astronomy · #Charged particle #Event generator #Geometry #Hadron #High-Energy Particle Collisions Research #Ion #Isotropy #Mathematics #Multiplicity (mathematics) #Nuclear physics #Particle physics #Particle physics theoretical and experimental studies #Physics #Proton #Quantum Chromodynamics and Particle Interactions #Quantum mechanics #Sphericity #Transverse plane #hep-ex
paper · pdf · doi:10.1140/epjc/s10052-012-2124-9
published as Eur. Phys. J. C 72 (2012) 2124 · 21 pages, 9 captioned figures, 3 tables, authors from page 16, published version, figures from http://aliceinfo.cern.ch/ArtSubmission/node/3080
openalex publication_date 2012/09/01 · openalex created_date 2016/06/24 · arxiv created 2017/04/15 · arxiv updated 2017/04/18 · openalex updated_date 2026/08/05
Measurements of the sphericity of primary charged particles in minimum bias proton-proton collisions at s = 0.9, 2.76 and 7 TeV with the ALICE detector at the LHC are presented. The observable is measured in the plane perpendicular to the beam direction using primary charged tracks with p T > 0.5 GeV/c in || < 0.8. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity (N ch ) is reported for events with different p T scales ("soft" and "hard") defined by the transverse momentum of the leading particle. In addition, the mean charged particle transverse momentum versus multiplicity is presented for the different event classes, and the sphericity distributions in bins of multiplicity are presented. The data are compared with calculations of standard Monte Carlo event generators. The transverse sphericity is found to grow with multiplicity at all collision energies, with a steeper rise at low N ch , whereas the event generators show an opposite tendency. The combined study of the sphericity and the mean p T with multiplicity indicates that most of the tested event generators produce events with higher multiplicity by generating more back-to-back jets resulting in decreased sphericity (and isotropy). The PYTHIA6 generator with tune PERUGIA-2011 exhibits a noticeable improvement in describing the data, compared to the other tested generators.