Searching for Jets in Heavy Ion Collisions

Jet quenching measurements using leading particles and their correlations suffer from known biases, which can be removed via direct reconstruction of jets in central heavy ion collisions. In this talk, we discuss several modern jet reconstruction algorithms and background subtraction techniques that are appropriate to heavy ion collisions.Comment: Proceedings of the 24th Winter Workshop on Nuclear Dynamics, South Padre Island, Texas, 5-12 April 200

High pTp_{T} inclusive hadron and photon spectra in pp and PbPb collisions

In this article, we report the inclusive charged hadron and isolated photon spectra at $\sqrt{s_{NN}}=2.76$ TeV PbPb collisions measured with the CMS detector at LHC. Charged particle momentum spectra are compared to a constructed reference measurement of proton-proton collisions at $\sqrt{s}=2.76$ TeV by using a combination of $x_T$ scaling and direct interpolation at fixed $p_{T}$. Photon results are compared to next to leading order calculations at the same center of mass energy. Nuclear modification factors ($R_{AA}$) are calculated to study the properties of the medium. While a large suppression is observed in the charged particle $R_{AA}$ at high transverse momentum, isolated photons show no modifications, revealing that PbPb collisions at $\sqrt{s_{NN}}=2.76$ TeV produce a strongly interacting colored medium.Comment: PANIC 2011 Meeting Proceeding

System and Energy Dependence of Strangeness Production with STAR

The yields and spectra of strange hadrons have each been measured by STAR as a function of centrality in $\rm \sqrt{s_{NN}}=$ 200 GeV AuAu collisions. By comparison to measurements in pp and dAu at $\rm \sqrt{s_{NN}}=200$ GeV and in AuAu at $\rm \sqrt{s_{NN}}=62$ GeV the dependence on system size and energy is studied. Short-lived resonances, such as $\Sigma (1385)$ and $\Lambda (1520)$, that may decay and regenerate in the medium, are used to examine the dynamical evolution between production and freeze-out for these systems. Particle production is investigated by comparison to thermal models, which assume a simple scaling of the yield with $\rm N_{part}$, in order to calculate the strangeness enhancement. Our hyperon measurements in AuAu indicate that $\rm N_{bin}$ may be a more appropriate scale for the strangeness correlation volume. In this case canonical suppression can not be simply parameterized with the geometrical overlap volume but will depend on the individual quark content of each particle. This theory is tested by comparing the data from different collision systems and centralities.Comment: Quark Matter 2005 Talk. Talk ppt file with further supporting plots can be found in http://qm2005.kfki.hu/talk2_select.pshtml?sel=10

Searching for Jets in Heavy Ion Collisions

Abstract. Jet quenching measurements using leading particles and their correlations suffer from known biases, which can be removed via direct reconstruction of jets in central heavy ion collisions. In this talk, we discuss several modern jet reconstruction algorithms and background subtraction techniques that are appropriate to heavy ion collisions