L. Adamczyk, AGH University of Science and Technology, Poland
James K. Adkins, University of KentuckyFollow
G. Agakishiev, Joint Institute for Nuclear Research, Russia
M. M. Aggarwal, Panjab University, India
Z. Ahammed, Variable Energy Cyclotron Centre, India
I. Alekseev, Alikhanov Institute for Theoretical and Experimental Physics, Russia
A. Aparin, Joint Institute for Nuclear Research, Russia
D. Arkhipkin, Brookhaven National Laboratory
E. C. Aschenauer, Brookhaven National Laboratory
A. Attri, Panjab University, India
G. S. Averichev, Joint Institute for Nuclear Research, Russia
X. Bai, Central China Normal University, China
V. Bairathi, National Institute of Science Education and Research, India
R. Bellwied, University of Houston
A. Bhasin, University of Jammu, India
A. K. Bhati, Panjab University, India
P. Bhattarai, University of Texas at Austin
J. Bielcik, Czech Technical University in Prague, Czech Republic
J. Bielcikova, Nuclear Physics Institute AS CR, Czech Republic
L. C. Bland, Brookhaven National Laboratory
I. G. Bordyuzhin, Alikhanov Institute for Theoretical and Experimental Physics, Russia
J. Bouchet, Kent State University
J. D. Brandenburg, Rice University
A. V. Brandin, National Research Nuclear Univeristy MEPhI, Russia
I. Bunzarov, Joint Institute for Nuclear Research, Russia
J. Butterworth, Rice University
H. Caines, Yale University
M. Calderón de la Barca Sánchez, University of California - Davis
J. M. Campbell, Ohio State University
D. Cebra, University of California - Davis
Renee H. Fatemi, University of KentuckyFollow
Suvarna Ramachandran, University of KentuckyFollow


We present measurements of Ω and ϕ production at midrapidity from Au+Au collisions at nucleon-nucleon center-of-mass energies √sNN = 7.7, 11.5, 19.6, 27, and 39 GeV by the STAR experiment at the BNL Relativistic Heavy Ion Collider (RHIC). Motivated by the coalescence formation mechanism for these strange hadrons, we study the ratios of N- + Ω−+) / [2N(ϕ)]. These ratios as a function of transverse momentum pT fall on a consistent trend at high collision energies, but start to show deviations in peripheral collisions at √sNN = 19.6, 27, and 39 GeV, and in central collisions at 11.5 GeV in the intermediate pT region of 2.4−3.6 GeV/c. We further evaluate empirically the strange quark pT distributions at hadronization by studying the Ω/ϕ ratios scaled by the number of constituent quarks (NCQ). The NCQ-scaled Ω/ϕ ratios show a suppression of strange quark production in central collisions at 11.5 GeV compared to √sNN ≥ 19.6 GeV. The shapes of the presumably thermal strange quark distributions in 0–60% most central collisions at 7.7 GeV show significant deviations from those in 0–10% most central collisions at higher energies. These features suggest that there is likely a change of the underlying strange quark dynamics in the transition from quark matter to hadronic matter at collision energies below 19.6 GeV.

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Published in Physical Review C, v. 93, issue 2, 021903, p. 1-6.

©2016 American Physical Society

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Due to the large number of authors, only the first 30 and the authors affiliated with the University of Kentucky are listed in the author section above. For the complete list of authors, please download this article.

The authors of this article are collectively known as STAR Collaboration.

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We thank the RHIC Operations Group and RCF at BNL, the NERSC Center at LBNL, the KISTI Center in Korea, and the Open Science Grid consortium for providing resources and support. We also thank Rudolph C. Hwa for valuable discussions. This work was supported in part by the Office of Nuclear Physics within the U.S. DOE Office of Science, the U.S. NSF, the Ministry of Education and Science of the Russian Federation, NNSFC, CAS, MoST (973 Program No. 2014CB845400) and MoE of China, the Korean Research Foundation, GA and MSMT of the Czech Republic, FIAS of Germany, DAE, DST, and UGC of India, the National Science Centre of Poland, National Research Foundation, the Ministry of Science, Education and Sports of the Republic of Croatia, and RosAtom of Russia.

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