Proton/pion ratios in Δϕ with respect to a jet in sNN=200GeV Au + Au collisions at STAR

Abstract Inclusive proton/pion ratios show an enhancement at intermediate transverse momentum ( p T ∼ 1.5 – 4.0 GeV / c ) in central s N N = 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 Δ ϕ between 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.