Beam-energy dependence of identified two-particle angular correlations in sNN=7.7–200 GeV Au+Au collisions

Author(s): Adam, J; Adamczyk, L; Adams, JR; Adkins, JK; Agakishiev, G; Aggarwal, MM; Ahammed, Z; Alekseev, I; Anderson, DM; Aparin, A; Aschenauer, EC; Ashraf, MU; Atetalla, FG; Attri, A; Averichev, GS; Bairathi, V; Barish, K; Bassill, AJ; Behera, A; Bellwied, R; Bhasin, A; Bielcik, J; Bielcikova, J; Bland, LC; Bordyuzhin, IG; Brandenburg, JD; Brandin, AV; Butterworth, J; Caines, H; Sanchez, M Calderon de la Barca; Cebra, D; Chakaberia, I; Chaloupka, P; Chan, BK; Chang, F-H; Chang, Z; Chankova-Bunzarova, N; Chatterjee, A; Chen, D; Chen, JH; Chen, X; Cheng, J; Cherney, M; Chevalier, M; Choudhury, S; Christie, W; Crawford, HJ; Csanad, M; Das, S; Daugherity, M; Dedovich, TG; Deppner, IM; Derevschikov, AA; Didenko, L; Dong, X; Drachenberg, JL; Dunlop, JC; Edmonds, T; Elsey, N; Engelage, J; Eppley, G; Esha, R; Esumi, S; Evdokimov, O; Ewigleben, J; Eyser, O; Fatemi, R; Fazio, S; Federic, P; Fedorisin, J; Feng, CJ; Feng, Y; Filip, P; Finch, E; Fisyak, Y; Francisco, A; Fulek, L; Gagliardi, CA; Galatyuk, T; Geurts, F; Gibson, A; Gopal, K; Grosnick, D; Guryn, W; Hamad, AI | Abstract: The two-particle angular correlation functions, $R_2$, of pions, kaons, and protons in Au+Au collisions at $\sqrt{s_{NN}}=$ 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV were measured by the STAR experiment at RHIC. These correlations were measured for both like-sign and unlike-sign charge combinations and versus the centrality. The correlations of pions and kaons show the expected near-side ({\it i.e.}, at small relative angles) peak resulting from short-range mechanisms. The amplitudes of these short-range correlations decrease with increasing beam energy. However, the proton correlation functions exhibit strong anticorrelations in the near-side region. This behavior is observed for the first time in an A+A collision system. The observed anticorrelation is $p_{T}$-independent and decreases with increasing beam energy and centrality. The experimental results are also compared to the Monte Carlo models UrQMD, Hijing, and AMPT.