Author(s): Castro, Nuno Filipe ; Onofre, A. ; ATLAS Collaboration
Date: 2013
Persistent ID: http://hdl.handle.net/1822/57600
Origin: RepositóriUM - Universidade do Minho
Project/scholarship: info:eu-repo/grantAgreement/FCT/3599-PPCDT/143069/PT ;
Subject(s): Heavy-ion collision; harmonic flow; event-by-event fluctuation; unfolding; Hadron-Hadron Scattering; Science & Technology; Ciências Naturais::Ciências Físicas
The distributions of event-by-event harmonic flow coefficients v (n) for n = 2- 4 are measured in = 2.76 TeV Pb + Pb collisions using the ATLAS detector at the LHC. The measurements are performed using charged particles with transverse momentum p (T) > 0.5 GeV and in the pseudorapidity range |eta| < 2.5 in a dataset of approximately 7 mu b(-1) recorded in 2010. The shapes of the v (n) distributions suggest that the associated flow vectors are described by a two-dimensional Gaussian function in central collisions for v (2) and over most of the measured centrality range for v (3) and v (4). Significant deviations from this function are observed for v (2) in mid-central and peripheral collisions, and a small deviation is observed for v (3) in mid-central collisions. In order to be sensitive to these deviations, it is shown that the commonly used multi-particle cumulants, involving four particles or more, need to be measured with a precision better than a few percent. The v (n) distributions are also measured independently for charged particles with 0.5 < p (T) < 1 GeV and p (T) > 1 GeV. When these distributions are rescaled to the same mean values, the adjusted shapes are found to be nearly the same for these two p (T) ranges. The v (n) distributions are compared with the eccentricity distributions from two models for the initial collision geometry: a Glauber model and a model that includes corrections to the initial geometry due to gluon saturation effects. Both models fail to describe the experimental data consistently over most of the measured centrality range.
We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWF and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF, DNSRC and Lundbeck Foundation, Denmark; EPLANET, ERC and NSRF, European Union; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, DFG, HGF, MPG and AvH Foundation, Germany; GSRT and NSRF, Greece; ISF, MINERVA, GIF, DIP and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; BRF and RCN, Norway; MNiSW, Poland; GRICES and FCT, Portugal; MERYS (MECTS), Romania; MES of Russia and ROSATOM, Russian Federation; JINR; MSTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DST/NRF, South Africa; MICINN, Spain; SRC and Wallenberg Foundation, Sweden; SER, SNSF and Cantons of Bern and Geneva, Switzerland; NSC, Taiwan; TAEK, Turkey; STFC, the Royal Society and Leverhulme Trust, United Kingdom; DOE and NSF, United States of America.
info:eu-repo/semantics/publishedVersion
