CERN Accelerating science

Article
Report number arXiv:1205.3963 ; CERN-PH-EP-2012-136 ; CERN-PH-EP-2012-136
Title Transverse sphericity of primary charged particles in minimum bias proton-proton collisions at s=0.9, 2.76 and 7 TeV
Author(s) ALICE Collaboration  Zeige alle 992 Autoren
Publication 2012-09-18
Imprint 11 May 2012
Number of pages 21
Note Comments: 21 pages, 11 figures
Long author list - awaiting processing
21 pages, 9 captioned figures, 3 tables, authors from page 16, published version, figures from http://aliceinfo.cern.ch/ArtSubmission/node/3080
In: Eur. Phys. J. C 72 (2012) 2124
DOI 10.1140/epjc/s10052-012-2124-9
Subject category Particle Physics - Experiment
Accelerator/Facility, Experiment CERN LHC ; ALICE
Free keywords QCD ; particle correlations and fluctuations ; experimental results ; event structure analysis ; pp collisions ; transverse sphericity ; multiplicity dependence
Abstract 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 linearized to be collinear safe and is measured in the plane perpendicular to the beam direction using primary charged tracks with pT0.5 GeV/c in |η|0.8. The mean sphericity as a function of the charged particle multiplicity at mid-rapidity (Nch) is reported for events with different pT 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 Nch, whereas the event generators show the opposite tendency. The combined study of the sphericity and the mean pT 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.
Copyright/License publication: © 2012-2024 CERN (License: CC-BY-3.0)
preprint: © 2012-2024 CERN (License: Open Access)



Corresponding record in: Inspire
Email contact: h.oeschler@gsi.de


 Datensatz erzeugt am 2012-05-11, letzte Änderung am 2024-11-27


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