Beam-energy dependence of the directed flow of deuterons in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Au</mml:mi><mml:mo>+</mml:mo><mml:mi>Au</mml:mi></mml:mrow></mml:math> collisions
J. Adam, L. Adamczyk, J. R. Adams, J. K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, D. M. Anderson, A. Aparin, E. C. Aschenauer, M. U. Ashraf, F. G. Atetalla, A. Attri, G. S. Averichev, V. Bairathi, K. N. Barish, A. Behera, R. Bellwied, A. Bhasin, J. Bielčík, J. Bielčíková, L. C. Bland, I. G. Bordyuzhin, J. D. Brandenburg, A. V. Brandin, J. M. Butterworth, H. Caines, M. Calderón de la Barca Sánchez, D. Cebra, I. Chakaberia, P. Chaloupka, B. K. Chan, F-H. Chang, Z. Chang, N. Chankova-Bunzarova, A. Chatterjee, D. Chen, C. H. Cheng, X. Chen, Z. Chen, J. Cheng, M. Cherney, M. Chevalier, S. Choudhury, W. Christie, X. Chu, H. J. Crawford, M. Csanád, M. Daugherity, Т. Г. Дедович, I. M. Deppner, A. A. Derevschikov, L. Didenko, X. Dong, J. L. Drachenberg, J. C. Dunlop, T. Edmonds, N. Elsey, J. Engelage, G. Eppley, S. Esumi, O. Evdokimov, A. Ewigleben, O. Eyser, R. Fatemi, S. Fazio, P. Federic, J. Fedorišin, C. Feng, Y. Feng, P. Filip, E. Finch, Y. Fisyak, A. Francisco, Ł. Fulek, C. A. Gagliardi, T. Galatyuk, F. J. M. Geurts, S. M. Gibson, K. Gopal, D. Grosnick, W. Guryn, A. I. Hamad, A. Hamed, S. Harabasz, J. W. Harris, Song He, W. He, X. H. He, S. Heppelmann, S. Heppelmann, N. Herrmann, E. Hoffman, L. Holub, Yang Hong, S. Horvat, Y. Hu, H. Z. Huang, S. L. Huang
Abstract
We present a measurement of the first-order azimuthal anisotropy ${v}_{1}$ of deuterons from $\text{Au}+\text{Au}$ collisions at $\sqrt{{s}_{NN}}=7.7$, 11.5, 14.5, 19.6, 27, and 39 GeV recorded with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The energy dependence of the ${v}_{1}(y)$ slope, $d{v}_{1}{/dy|}_{y=0}$, for deuterons, where $y$ is the rapidity, is extracted for semicentral collisions (10%--40% centrality) and compared with that of protons. While the ${v}_{1}(y)$ slopes of protons are generally negative for $\sqrt{{s}_{NN}}>10\phantom{\rule{4pt}{0ex}}\mathrm{GeV}$, those for deuterons are consistent with zero, a strong enhancement of the ${v}_{1}(y)$ slope of deuterons is seen at the lowest collision energy (the largest baryon density) at $\sqrt{{s}_{NN}}=7.7\phantom{\rule{4pt}{0ex}}\mathrm{GeV}$. In addition, we report the transverse momentum dependence of ${v}_{1}$ for protons and deuterons. The experimental results are compared with transport and coalescence models.