scholarly journals Event Plane Dependence of Jet-Hadron Correlations in Au–Au Collisions at √sNN = 200 GeV with the STAR Detector at RHIC

Proceedings ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 21
Author(s):  
Joel Mazer
Keyword(s):  
Path Length ◽  
Heavy Ion ◽  
Jet Quenching ◽  
Dense Medium ◽  
Complex Flow ◽  
Event Plane ◽  
Length Dependence ◽  
200 Gev ◽  
Medium Modifications ◽  
Star Detector

The phenomenon of jet quenching indicates that partons lose energy as they traverse the hot dense medium. By restricting a trigger jet in azimuth relative to the event plane, we are given another tool, which allows us to study the path length dependence of medium modifications. Measurements of angular correlations relative to the event plane between reconstructed R = 0 . 4 full jets and charged hadrons are presented in mid-peripheral Au–Au collisions at s N N = 200 GeV with the STAR detector at RHIC. A robust and precise method, known as the Reaction Plane Fit (RPF) method is used to remove the complex, flow-dominated heavy-ion background from the correlation functions. Quantified through yield ratios, we study the event plane dependence of jet-correlated yields. The yield ratios are compared to prior measurements made by the ALICE Collaboration in Pb–Pb collisions at s N N = 2 . 76 TeV. With increased statistics and smaller uncertainties, the results from STAR show a similar conclusion to that of ALICE, that within uncertainties this measurement shows no significant path length dependence of medium modifications.

scholarly journals Reconstruction of neutral-triggered charged recoil jets in √s = 200 GeV p+p collisions at the STAR experiment

2020 ◽  
Vol 235 ◽  
pp. 05005
Author(s):  
Derek Anderson
Keyword(s):  
Energy Loss ◽  
Path Length ◽  
Heavy Ion ◽  
Particle Dynamics ◽  
Dense Medium ◽  
Direct Photons ◽  
Ion Collisions ◽  
200 Gev ◽  
Star Experiment ◽  
Shed Light

Jets — collimated sprays of hadrons — are produced by hard-scattered partons during the early stages of heavy ion collisions. Hence, they provide a valuable probe of the complex multi-particle dynamics within the hot, dense medium produced in such collisions. In particular, the study of jets recoiling from direct photons (γdir+jet) and those recoiling from energetic π0 (π0+jet) may shed light on the path-length and initial flavor (quark vs. gluon) dependence of the energy-loss experienced by a parton as it traverses the medium. We present here measurements of the yields of charged recoil jets tagged by γdir and π0 in p+p collisions at √S = 200 GeV. These measurements will serve as a vacuum fragmentation reference for an upcoming measurement in Au + Au collisions.

scholarly journals JET MEASUREMENTS IN p+p AND D+Au COLLISIONS WITH STAR AT RHIC

2011 ◽  
Vol 20 (07) ◽  
pp. 1651-1655
Author(s):  
◽  
JAN KAPITÁN
Keyword(s):  
Quantitative Study ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Jet Quenching ◽  
Dense Medium ◽  
Initial State ◽  
Ion Collisions ◽  
Promising Tool ◽  
200 Gev ◽  
Nuclear Effects

Full jet reconstruction in heavy-ion collisions is a promising tool for the quantitative study of properties of the dense medium produced at RHIC. In addition to baseline measurements in p + p , results from d + Au collisions are needed to disentangle initial state nuclear effects from medium-induced k T broadening and jet quenching. We present mid-rapidity inclusive jet p T spectra and di-jet correlations (k T ) in 200 GeV p + p and d + Au collisions from the 2007-2008 RHIC run.

scholarly journals The global geometrical property of jet events in high-energy nuclear collisions

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Shi-Yong Chen ◽  
Wei Dai ◽  
Shan-Liang Zhang ◽  
Qing Zhang ◽  
Ben-Wei Zhang
Keyword(s):  
Energy Loss ◽  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
High Energy ◽  
Jet Quenching ◽  
Relativistic Heavy Ion Collisions ◽  
Parton Energy Loss ◽  
Boltzmann Transport ◽  
Ion Collisions ◽  
Medium Modifications

AbstractWe present the first theoretical study of medium modifications of the global geometrical pattern, i.e., transverse sphericity ($$S_{\perp }$$ S ⊥ ) distribution of jet events with parton energy loss in relativistic heavy-ion collisions. In our investigation, POWHEG + PYTHIA is employed to make an accurate description of transverse sphericity in the p + p baseline, which combines the next-to-leading order (NLO) pQCD calculations with the matched parton shower (PS). The Linear Boltzmann Transport (LBT) model of the parton energy loss is implemented to simulate the in-medium evolution of jets. We calculate the event normalized transverse sphericity distribution in central Pb + Pb collisions at the LHC, and give its medium modifications. An enhancement of transverse sphericity distribution at small $$S_{\perp }$$ S ⊥ region but a suppression at large $$S_{\perp }$$ S ⊥ region are observed in A + A collisions as compared to their p + p references, which indicates that in overall the geometry of jet events in Pb + Pb becomes more pencil-like. We demonstrate that for events with 2 jets in the final-state of heavy-ion collisions, the jet quenching makes the geometry more sphere-like with medium-induced gluon radiation. However, for events with $$\ge 3$$ ≥ 3 jets, parton energy loss in the QCD medium leads to the events more pencil-like due to jet number reduction, where less energetic jets may lose their energies and then fall off the jet selection kinematic cut. These two effects offset each other and in the end result in more jetty events in heavy-ion collisions relative to that in p + p.

scholarly journals Coherent e+e- production at very low transverse momentum at STAR

2018 ◽  
Vol 171 ◽  
pp. 18016 ◽  
Author(s):  
Chi Yang
Keyword(s):  
Theoretical Model ◽  
Transverse Momentum ◽  
Pair Production ◽  
Spectral Function ◽  
Model Calculation ◽  
Heavy Ion ◽  
Relativistic Heavy Ion Collider ◽  
200 Gev ◽  
Star Detector

We report the measurements of e+e- pair production at very low e+e- pair transverse momentum (pT < 0.15 GeV/c) in Au+Au collisions at [see formula in PDF] = 200 GeV and U+U collisions at [see formula in PDF] = 193 GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 60-80% centrality, significant excesses are observed with respect to hadronic cocktails in both Au+Au and U+U collisions. These excess yields can not be explained by a theoretical model calculation incorporating in-medium broadened ρ spectral function. Additionally, the [see formula in PDF] distribution for excess yield is shown and found to be exponential at very low pT.

scholarly journals The dijet mass distribution in heavy ion collisions

2020 ◽  
Vol 235 ◽  
pp. 05006
Author(s):  
Jared Reiten
Keyword(s):  
Heavy Ion Collisions ◽  
Heavy Ion ◽  
Jet Quenching ◽  
Heavy Flavor ◽  
Relativistic Heavy Ion Collider ◽  
Mass Distributions ◽  
Ion Collisions ◽  
Heavy Quark Mass ◽  
200 Gev ◽  
Momentum Imbalance

In these proceedings, we review the production of both light and heavy flavor dijets in heavy ion collisions and highlight a promising observable to expose their distinct signatures. We propose the modification of dijet invariant mass distributions in heavy ion collisions as a new observable that exhibits striking sensitivity to the heavy quark mass dependence of in-medium parton showers. This observable has the advantage of amplifying the effects of jet quenching in contrast to conventional observables, such as the dijet momentum imbalance shift, which involve cancellations of such effects and, hence, result in less pronounced signals. Predictions are presented for Au+Au collisions at √SNN = 200 GeV to guide the future sPHENIX program at the Relativistic Heavy Ion Collider.

scholarly journals RESULTS FROM PHENIX AT RHIC WITH IMPLICATIONS FOR LHC

2011 ◽  
Vol 26 (32) ◽  
pp. 5299-5335 ◽  
Author(s):  
M. J. TANNENBAUM
Keyword(s):  
Heavy Ion ◽  
Jet Quenching ◽  
Dense Medium ◽  
Particle Multiplicity ◽  
Hard Scattering ◽  
Relativistic Heavy Ion Collider ◽  
Proton Proton ◽  
Proton Collisions ◽  
Energy Formula ◽  
Proton Proton Collisions

Results from the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) in nucleus–nucleus and proton–proton collisions at c.m. energy [Formula: see text] are presented in the context of the methods of single and two-particle inclusive reactions which were used in the discovery of hard-scattering in p–p collisions at the CERN ISR in the 1970's. These techniques are used at RHIC in A + A collisions because of the huge combinatoric background from the large particle multiplicity. Topics include J/Ψ suppression, jet quenching in the dense medium (sQGP) as observed with π0 at large transverse momentum, thermal photons, collective flow, two-particle correlations, suppression of heavy quarks at large pT and its possible relation to Higgs searches at the LHC. The differences and similarities of the measurements in p–p and A + A collisions are presented. The two discussion sessions which followed the lectures on which this article is based are included at the end.

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