Transverse-Momentum Spectra inAu+Auandd+AuCollisions at

Abstract

We present spectra of charged hadrons from Au+Au and d+Au collisions at sqrt[s(NN)]=200 GeV measured with the BRAHMS experiment at RHIC. The spectra for different collision centralities are compared to spectra from p+(-)p collisions at the same energy scaled by the number of binary collisions. The resulting ratios (nuclear modification factors) for central Au+Au collisions at eta=0 and eta=2.2 evidence a strong suppression in the high p(T) region (>2 GeV/c). In contrast, the d+Au nuclear modification factor (at eta=0) exhibits an enhancement of the high p(T) yields. These measurements indicate a high energy loss of the high p(T) particles in the medium created in the central Au+Au collisions. The lack of suppression in d+Au collisions makes it unlikely that initial state effects can explain the suppression in the central Au+Au collisions.

Transverse momentum broadening and the jet quenching parameter, redux

“…Þ is not that of a standard Wilson loop-the operators (like the color matrices) are path ordered, whereas in a standard Wilson loop operators are time ordered. This subtlety, which had not been noticed 1 Throughout this paper, k ? is the two-dimensional vectork ?…”

“…One of the central discoveries made in experimental heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is that the droplets of quark-gluon plasma produced in these collisions are sufficiently strongly coupled that they are able to ''quench jets'' [1][2][3][4]. That is, when a very energetic quark or gluon (energetic enough that if it were in vacuum it would manifest itself as a jet, and with an energy that is much greater than the temperature of the medium in which it finds itself) plows through the strongly coupled plasma, it loses sufficient energy that few high momentum hadrons are seen in the final state.…”

Measurement of the groomed jet mass in PbPb and pp collisions at $$ \sqrt{s_{\mathrm{NN}}}=5.02 $$ TeV

“…In heavy ion collisions, scattering processes with large momentum transfer Q (of order 100 GeV or more) between the partonic constituents of the colliding nuclei occur early. Energy loss experienced by these high-momentum partons (quarks or gluons) as a result of their interactions with the colored, hot and dense quantum chromodynamics (QCD) medium created in heavy ion collisions (the quark-gluon plasma, or QGP) [1,2], was first observed at BNL RHIC [3][4][5][6] and then at the CERN LHC [7][8][9]. Interactions of the outgoing partons with the QGP are also expected to modify the angular and momentum distributions of the parton shower relative to proton-proton (pp) collisions.…”

Inclusiveπ0,η, and direct photon production at high transverse momentum inp+pAbelev1, Aggarwal2, Ahammed3 et al. 2010Phys. Rev. CSelf Cite393130View full textAdd to dashboardCite

“…Furthermore, it was found that jetlike correlations opposite to trigger jets are suppressed and that the azimuthal anisotropy in hadron emission persists out to very high p T [2][3][4]. In contrast, no suppression effects were seen in d + Au collisions [5][6][7][8], which has led to the conclusion that the observations made in Au + Au are attributable to the high-density medium produced in such collisions and not to initial-state effects. The most probable explanation to date is that the suppression is attributable to parton energy loss from induced gluon radiation (jet quenching) in the extremely hot and dense medium [9].…”