Abstract
The STAR Collaboration at the Relativistic Heavy Ion Collider reports the first measurement of inclusive jet production in peripheral and central Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. Jets are reconstructed with the anti-k$_{T}$ algorithm using charged tracks with pseudorapidity $|\eta|<1.0$ and transverse momentum $0.2<p_{T,jet}^{ch}<30$ GeV/$c$, with jet resolution parameter $R$=0.2, 0.3, and 0.4. The large background yield uncorrelated with the jet signal is observed to be dominated by statistical phase space, consistent with a previous coincidence measurement. This background is suppressed by requiring a high-transverse-momentum (high-$p_T$) leading hadron in accepted jet candidates. The bias imposed by this requirement is assessed, and the $p_T$ region in which the bias is small is identified. Inclusive charged-particle jet distributions are reported in peripheral and central Au+Au collisions for $5<p_{T,jet}^{ch}<25$ GeV/$c$ and $5<p_{T,jet}^{ch}<30$ GeV/$c$, respectively. The charged-particle jet inclusive yield is suppressed for central Au+Au collisions, compared to both the peripheral Au+Au yield from this measurement and to the $pp$ yield calculated using the PYTHIA event generator. The magnitude of the suppression is consistent with that of inclusive hadron production at high $p_T$, and that of semi-inclusive recoil jet yield when expressed in terms of energy loss due to medium-induced energy transport. Comparison of inclusive charged-particle jet yields for different values of $R$ exhibits no significant evidence for medium-induced broadening of the transverse jet profile for $R<0.4$ in central Au+Au collisions. The measured distributions are consistent with theoretical model calculations that incorporate jet quenching.
Highlights
Collisions of heavy nuclei at high energy generate a quarkgluon plasma (QGP), a state of matter with temperature and energy density similar to those of the universe a few microseconds after the Big Bang and whose dynamics are governed by the interactions of subhadronic quanta ([1] and references therein)
Charged-particle jet yield suppression is quantified by comparing the quasi-inclusive distribution measured in central Au+Au collisions to that measured in peripheral Au+Au collisions and to the inclusive charged-particle jet distribution for pp collisions generated using the PYTHIA Monte Carlo generator [50], which has been validated by comparison to inclusive measurements of pions and fully reconstructed jets at Relativistic Heavy Ion Collider (RHIC) [51]
In this paper we explore a related approach to describe the uncorrelated background to the inclusive jet distribution, utilizing a parametrized model (PM) calculation that accurately describes the eventwise distributions of mean-pT and mean transverse energy ( ET ) in highenergy nuclear collisions [71,72,73]
Summary
Collisions of heavy nuclei at high energy generate a quarkgluon plasma (QGP), a state of matter with temperature and energy density similar to those of the universe a few microseconds after the Big Bang and whose dynamics are governed by the interactions of subhadronic quanta ([1] and references therein). The distribution of the jet population arising from the large uncorrelated background is well described by a model calculation based on statistical phase space, without taking into account any multiparticle correlations whatsoever This observation is consistent with the accurate description of the background to semi-inclusive recoil jet yields by event mixing [48]. Charged-particle jet yield suppression is quantified by comparing the quasi-inclusive distribution measured in central Au+Au collisions to that measured in peripheral Au+Au collisions and to the inclusive charged-particle jet distribution for pp collisions generated using the PYTHIA Monte Carlo generator [50], which has been validated by comparison to inclusive measurements of pions and fully reconstructed jets at RHIC [51] These measurements are compared to similar inclusive jet measurements at the LHC, to semi-inclusive hadron+jet measurements at RHIC, and to theoretical calculations of jet quenching.
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