arXiv · 2503.23665
Measurement of Kaon Directed Flow in Au+Au Collisions in the High Baryon Density Region
Abstract
Rapidity-odd directed flow $v_1$ measurements are presented for $K^{\pm}$ and $K^0_S$ in Au$+$Au collisions at $\sqrt{s_{\text{NN}}}$ = 3.0, 3.2, 3.5, and 3.9 GeV with the STAR experiment. For comparison, $v_1$ of $\pi^{\pm}$, protons, and $\Lambda$ from the same collisions are also discussed. The mid-rapidity $v_1$ slope $\text{d}v_1/\text{d}y|_{y=0}$ for protons and $\Lambda$ is positive in these collisions. On the other hand, $v_1$ slope of kaons exhibits a strong $p_\text{T}$ dependence: negative at $p_\text{T} <$ 0.6 GeV/$c$ and positive at higher $p_\text{T}$. A similar $p_\text{T}$ dependence is also evident for the $v_1$ slope of charged pions. Compared to the spectator-removed calculations in Au$+$Au collisions at $\sqrt{s_{\text{NN}}} =$ 3.0-3.9 GeV, the JAM model demonstrates a pronounced shift of the $v_1$ slopes of mesons towards the negative direction. It suggests that the shadowing effect of the spectators plays an important role in the observed kaon anti-flow at low $p_\text{T}$ in the high baryon density region of non-central collisions.
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STAR Collaboration, B. E. Aboona, J. Adam, G. Agakishiev, I. Aggarwal, M. M. Aggarwal, Z. Ahammed, A. Aitbayev, I. Alekseev, E. Alpatov, A. K. Alshammri, A. Aparin, S. Aslam, J. Atchison, G. S. Averichev, V. Bairathi, X. Bao, P. Barik, K. Barish, S. Behera, P. Bhagat, A. Bhasin, S. Bhatta, I. G. Bordyuzhin, J. D. Brandenburg, A. V. Brandin, C. Broodo, X. Z. Cai, H. Caines, M. Calderón de la Barca Sánchez, D. Cebra, J. Ceska, I. Chakaberia, Y. S. Chang, Z. Chang, A. Chatterjee, D. Chen, J. H. Chen, L. Chen, Q. Chen, W. Chen, Z. Chen, J. Cheng, Y. Cheng, W. Christie, X. Chu, S. Corey, H. J. Crawford, G. Dale-Gau, A. Das, D. De Souza Lemos, T. G. Dedovich, I. M. Deppner, A. A. Derevschikov, A. Deshpande, A. Dhamija, A. Dimri, P. Dixit, X. Dong, J. L. Drachenberg, E. Duckworth, J. C. Dunlop, Y. S. El-Feky, J. Engelage, G. Eppley, S. Esumi, O. Evdokimov, O. Eyser, B. Fan, Y. Fang, R. Fatemi, S. Fazio, H. Feng, Y. Feng, E. Finch, Y. Fisyak, F. A. Flor, B. Fu, C. Fu, T. Fu, T. Gao, Y. Gao, G. Garcia, F. Geurts, A. Gibson, A. Giri, K. Gopal, X. Gou, D. Grosnick, A. Gu, J. Gu, A. Gupta, A. Hamed, R. J. Hamilton, J. Han, X. Han, M. D. Harasty, J. W. Harris, H. Harrison-Smith, L. B. Havener. 2025-03-31. Measurement of Kaon Directed Flow in Au+Au Collisions in the High Baryon Density Region. https://doi.org/10.1016/j.physletb.2026.140353
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