Measurements of the Nuclear Modification Factor for Jets inPb+PbCollisions atsNN=2.76  TeVwith the ATLAS Detector

Abstract

Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at √(s)NN=2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 and 0.14 nb(-1), respectively. The jets are identified with the anti-k(t) algorithm with R=0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32<p(T)<500 GeV and absolute rapidity |y|<2.1 and as a function of collision centrality. The nuclear modification factor R(AA) is evaluated, and jets are found to be suppressed by approximately a factor of 2 in central collisions compared to pp collisions. The R(AA) shows a slight increase with p(T) and no significant variation with rapidity.

Measurement of charged-particle spectra in Pb+Pb collisions at s N N = 2.76 $$ \sqrt{s_{\mathrm{NN}}}=2.76 $$ TeV with the ATLAS detector at the LHC

“…At fixed p T , the R AA values are consistent with a flat behaviour in |η|, within the statistical and systematic uncertainties, in the pseudorapidity range |η| < 2. A similar flat behaviour was found for jet R AA as well [9], although the p T dependence is very different.…”

“…At fixed p T , the R AA values are consistent with a flat behaviour in |η|, within the statistical and systematic uncertainties, in the pseudorapidity range |η| < 2. A similar flat behaviour was found for jet R AA as well [9], although the p T dependence is very different.The R AA values decrease with increasing N part in all measured p T intervals, but the N part dependence is strongest around the minimum of R AA (p T ≈ 7 GeV) and weakest in the p T region above 60 GeV.-30 - …”

“…N part measured with the jets of comparable energy [9], both distributions show similar trend. They have also similar values for peripheral collisions, but in the more central collisions the jet R AA reaches lower values.…”

“…collisions with respect to the yield in pp collisions by factor of two to four [9,10]. Additional important information about the energy-loss mechanism is provided by the study of jet fragmentation functions [11,12].…”

Origins of the di-jet asymmetry in heavy-ion collisions

“…The ability to systematically reconstruct jets above the large and fluctuating background present in ultra-relativistic heavy-ion collisions [1] has opened up a versatile path [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] to study the properties of Quark Gluon Plasma (QGP). Jets are sensitive, through the wide range of scales involved in their development, to a variety of properties of the expanding QGP they traverse.…”