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Title: Flow and interferometry results from Au + Au collisions at s N N = 4.5 GeV

Journal Article · · Physical Review. C
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The beam energy scan (BES) program at the Relativistic Heavy Ion Collider (RHIC) was extended to energies below √ sNN = 7.7 GeV in 2015 by successful implementation of the fixed-target mode 3 of operation in the STAR (Solenoidal Tracker At RHIC) experiment. In this mode, ions circulate in one ring of the collider and interact with a stationary target at the entrance of the STAR Time Projection Chamber. The first results for Au+Au collisions at √ sNN = 4.5 GeV are presented, demonstrating good performance of all the relevant detector subsystems in fixed-target mode. Results presented here include directed and elliptic flow of identified hadrons, and radii from pion femtoscopy. The latter, together with recent HADES results, reveal a long-sought peak structure that may be caused by the system evolving through a first-order phase transition from quark-gluon plasma to the hadronic phase. Directed and elliptic flow for pions are presented for the first time at this beam energy. Pion and proton elliptic flow show behavior which hints at constituent quark scaling, and demonstrate that a definitive conclusion will be achievable using the full statistics of the on-going second phase of BES (BES-II). In particular, BES-II to date has recorded fixed-target data sets with two orders of magnitude more events at each of nine energies between √ sNN = 3.0 and 7.7 GeV.

Research Organization:
Brookhaven National Laboratory (BNL), Upton, NY (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP); USDOE Office of Science (SC), High Energy Physics (HEP)
Contributing Organization:
STAR Collaboration
Grant/Contract Number:
SC0012704; AC02-05CH11231
OSTI ID:
1646589
Alternate ID(s):
OSTI ID: 1830340
Report Number(s):
BNL-216220-2020-JAAM; TRN: US2202764
Journal Information:
Physical Review. C, Vol. 103, Issue 3; ISSN 2469-9985
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

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