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arXiv · 1207.7156

Proton/Pion ratios in Δϕwith respect to a jet in sqrt{s_{NN}} =200 GeV Au+Au collisions at STAR

Alán Dávila
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Abstract

Inclusive Proton/pion ratios show an enhancement at intermediate transverse momentum (P_{T} ~ 1.5 - 4.0 GeV/c) in central sqrt{s_{NN}} = 200 GeV Au+Au collisions compared to peripheral Au+Au and p+p collisions. This effect suggests a production mechanism, different from fragmentation, which is consistent with coalescence and recombination models. A high E_{T} trigger particle selects a surface-biased jet, which is measured to have a similar p_{T} distribution as a p+p jet. This jet is used to enhance the quenching effects of the recoiling, medium traversing one. We reconstruct the trigger jet using the FASTJET algorithm, with a E_{T} (p_{T}) cut of 3.0 GeV(/c) on the towers(tracks) in order to reduce the heavy-ion collision background. The particle identification of tracks with p_{T} up to ~ 2.8 GeV/c is obtained by taking advantage of STAR TOF and TPC detectors with full azimuth coverage. Correlations in Δϕbetween jets and identified hadrons are presented, and the particle ratios in different regions of azimuth are measured. Particle ratios associated with the trigger jet vs. the recoil jet, and comparisons to inclusive particle ratios can help to distinguish between jet-related (vacuum and medium-modified) and bulk-related contributions to the ratios enhancement.

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Alán Dávila. 2012-09-21. Proton/Pion ratios in Δϕwith respect to a jet in sqrt{s_{NN}} =200 GeV Au+Au collisions at STAR. https://doi.org/10.1016/j.nuclphysa.2012.12.018

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