We present measurements of π− and π+ elliptic flow, v2, at midrapidity in Au+Au collisions at √SNN=200, 62.4, 39, 27, 19.6, 11.5, and 7.7 GeV, as a function of event-by-event charge asymmetry, Ach, based on data from the STAR experiment at RHIC. We find that π− (π+) elliptic flow linearly increases (decreases) with charge asymmetry for most centrality bins at √SNN=27 GeV and higher. At √SNN=200 GeV, the slope of the difference of v2 between π− and π+ as a function of Ach exhibits a centrality dependence, which is qualitatively similar to calculations that incorporate a chiral magnetic wave effect. Similar centrality dependence is also observed at lower energies.
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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. 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 Center of Poland, National Research Foundation, the Ministry of Science, Education and Sports of the Republic of Croatia, and RosAtom of Russia.
Adkins, J. Kevin; Fatemi, Renee; Ramachandran, Suvarna; Adamczyk, L.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alekseev, I.; Alford, J.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; and Averichev, G. S., "Observation of Charge Asymmetry Dependence of Pion Elliptic Flow and the Possible Chiral Magnetic Wave in Heavy-Ion Collisions" (2015). Physics and Astronomy Faculty Publications. 323.