Baryonic resonance studies with STAR

Abstract

Abstract. Yields and spectra of Σ(1385) are measured in p + p, d + Au and Au + Au collisions at √ s NN =200 GeV. The nuclear modification factors in d + Au collisions are presented. The p T dependent medium effects are investigated via the nuclear modification factors. The implications of these results on various models are discussed.

Reconstructing Σ0decays in STAR

“…Typical comparisons of data from nuclear collisions to particle production models require a caveat for (anti)Λ yields from experimental inability to separate the contributions of those yields from Σ state decays. Recent analysis in STAR is leading toward resolving the contribution from excited Σ states [1], but the bulk contribution comes from electromagnetic decays of the (anti)Σ 0 . In the STAR detector, photon conversions into e + e − pairs in the detector material have been used to identify photons from π 0 decays [2].…”

Hard Probes with the STAR Experiment

“…The φ [ 29] and K * [ 30], mesons with masses similar to the proton, follow the behavior of the mesons, proving that this separation is not due to mass. Such common grouping is violated in R AA , in which the reference is from p+p collisions rather than peripheral collisions: strong enhancement in strange baryon R AA is seen at intermediate p T , with increasing enhancement for increasing strangeness content [ 26]. There were indications in previous results that these dependences on hadron species disappeared at high p T [ 24], but the increased reach of the run 4 dataset strengthens this conclusion, placing the application of models incorporating parton energy loss on solid ground for p T >∼ 6 GeV/c.…”

Jet Observables of Parton Energy Loss in High-Energy Nuclear Collisions

“…Here r, R are Lorentz-invariant opening angles, 2 in a cone algorithm, and i represents a sum over all particles in this jet. With the above definition we have Ψ int (R; R) = 1.…”

“…However, at present, most measurements of hard processes are limited to inclusive hadron (or photon) production and di-hadron (or gamma-hadron) correlations, which are only the leading fragments of a jet. Thus their measurement may suffer from geometric biases [2]. With the upgrades at the RHIC experimental facilities and the new opportunities provided by LHC, much more differential studies of parton energy loss in nuclei will become available -the ability to investigate the full structures of a jet in relativistic heavy-ion collisions [3,4].…”