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1. Measurement of the central exclusive production of charged particle pairs in proton-proton collisions at s $$ \sqrt{s} $$ = 200 GeV with the STAR detector at RHIC

Author

The STAR collaboration, 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. Barish, A. Behera, R. Bellwied, A. Bhasin, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. D. Brandenburg, A. V. Brandin, J. 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, J. H. Chen, X. Chen, Z. Chen, J. Cheng, M. Cherney, M. Chevalier, S. Choudhury, W. Christie, X. Chu, H. J. Crawford, M. Csanád, M. Daugherity, T. G. Dedovich, I. M. Deppner, A. A. Derevschikov, L. Didenko, X. Dong, J. L. Drachenberg, J. C. Dunlop, T. Edmonds, N. Elsey, J. Engelage, G. Eppley, R. Esha, S. Esumi, O. Evdokimov, A. Ewigleben, O. Eyser, R. Fatemi, S. Fazio, P. Federic, J. Fedorisin, C. J. Feng, Y. Feng, P. Filip, E. Finch, Y. Fisyak, A. Francisco, L. Fulek, C. A. Gagliardi, T. Galatyuk, F. Geurts, A. Gibson, K. Gopal, D. Grosnick, W. Guryn, A. I. Hamad, A. Hamed, S. Harabasz, J. W. Harris, S. He, W. He, X. H. He, S. Heppelmann, N. Herrmann, E. Hoffman, L. Holub, Y. Hong, S. Horvat, Y. Hu, H. Z. Huang, S. L. Huang, T. Huang, X. Huang, T. J. Humanic, P. Huo, G. Igo, D. Isenhower, W. W. Jacobs, C. Jena, A. Jentsch, Y. JI, J. Jia, K. Jiang, S. Jowzaee, X. Ju, E. G. Judd, S. Kabana, M. L. Kabir, S. Kagamaster, D. Kalinkin, K. Kang, D. Kapukchyan, K. Kauder, H. W. Ke, D. Keane, A. Kechechyan, M. Kelsey, Y. V. Khyzhniak, D. P. Kikoła, C. Kim, B. Kimelman, D. Kincses, T. A. Kinghorn, I. Kisel, A. Kiselev, A. Kisiel, M. Kocan, L. Kochenda, L. K. Kosarzewski, L. Kramarik, P. Kravtsov, K. Krueger, N. Kulathunga Mudiyanselage, L. Kumar, R. Kunnawalkam Elayavalli, J. H. Kwasizur, R. Lacey, S. Lan, J. M. Landgraf, J. Lauret, A. Lebedev, R. Lednicky, J. H. Lee, Y. H. Leung, C. Li, W. Li, X. Li, Y. Li, Y. Liang, R. Licenik, T. Lin, Y. Lin, M. A. Lisa, F. Liu, H. Liu, P. Liu, T. Liu, X. Liu, Y. Liu, Z. Liu, T. Ljubicic, W. J. Llope, R. S. Longacre, N. S. Lukow, S. Luo, X. Luo, G. L. Ma, L. Ma, R. Ma, Y. G. Ma, N. Magdy, R. Majka, D. Mallick, S. Margetis, C. Markert, H. S. Matis, J. A. Mazer, N. G. Minaev, S. Mioduszewski, B. Mohanty, M. M. Mondal, I. Mooney, Z. Moravcova, D. A. Morozov, M. Nagy, J. D. Nam, Md. Nasim, K. Nayak, D. Neff, J. M. Nelson, D. B. Nemes, M. Nie, G. Nigmatkulov, T. Niida, L. V. Nogach, T. Nonaka, A. S. Nunes, G. Odyniec, A. Ogawa, S. Oh, V. A. Okorokov, B. S. Page, R. Pak, A. Pandav, Y. Panebratsev, B. Pawlik, D. Pawlowska, H. Pei, C. Perkins, L. Pinsky, R. L. Pintér, J. Pluta, J. Porter, M. Posik, N. K. Pruthi, M. Przybycien, J. Putschke, H. Qiu, A. Quintero, S. K. Radhakrishnan, S. Ramachandran, R. L. Ray, R. Reed, H. G. Ritter, J. B. Roberts, O. V. Rogachevskiy, J. L. Romero, L. Ruan, J. Rusnak, N. R. Sahoo, H. Sako, S. Salur, J. Sandweiss, S. Sato, W. B. Schmidke, N. Schmitz, B. R. Schweid, F. Seck, J. Seger, M. Sergeeva, R. Seto, P. Seyboth, N. Shah, E. Shahaliev, P. V. Shanmuganathan, M. Shao, F. Shen, W. Q. Shen, S. S. Shi, Q. Y. Shou, E. P. Sichtermann, R. Sikora, M. Simko, J. Singh, S. Singha, N. Smirnov, W. Solyst, P. Sorensen, H. M. Spinka, B. Srivastava, T. D. S. Stanislaus, M. Stefaniak, D. J. Stewart, M. Strikhanov, B. Stringfellow, A. A. P. Suaide, M. Sumbera, B. Summa, X. M. Sun, X. Sun, Y. Sun, B. Surrow, D. N. Svirida, P. Szymanski, A. H. Tang, Z. Tang, A. Taranenko, T. Tarnowsky, J. H. Thomas, A. R. Timmins, D. Tlusty, M. Tokarev, C. A. Tomkiel, S. Trentalange, R. E. Tribble, P. Tribedy, S. K. Tripathy, O. D. Tsai, Z. Tu, T. Ullrich, D. G. Underwood, I. Upsal, G. Van Buren, J. Vanek, A. N. Vasiliev, I. Vassiliev, F. Videbæk, S. Vokal, S. A. Voloshin, F. Wang, G. Wang, J. S. Wang, P. Wang, Y. Wang, Z. Wang, J. C. Webb, P. C. Weidenkaff, L. Wen, G. D. Westfall, H. Wieman, S. W. Wissink, R. Witt, Y. Wu, Z. G. Xiao, G. Xie, W. Xie, H. Xu, N. Xu, Q. H. Xu, Y. F. Xu, Y. Xu, Z. Xu, C. Yang, Q. Yang, S. Yang, Y. Yang, Z. Yang, Z. Ye, L. Yi, K. Yip, H. Zbroszczyk, W. Zha, D. Zhang, S. Zhang, X. P. Zhang, Y. Zhang, Z. J. Zhang, Z. Zhang, J. Zhao, C. Zhong, C. Zhou, X. Zhu, Z. Zhu, M. Zurek, and M. Zyzak

Subjects
Diffraction, Forward physics, Hadron-Hadron scattering (experiments), Nuclear and particle physics. Atomic energy. Radioactivity, QC770-798
Abstract

Abstract We report on the measurement of the Central Exclusive Production of charged particle pairs h + h − (h = π, K, p) with the STAR detector at RHIC in proton-proton collisions at s $$ \sqrt{s} $$ = 200 GeV. The charged particle pairs produced in the reaction pp → p′ + h + h − + p′ are reconstructed from the tracks in the central detector and identified using the specific energy loss and the time of flight method, while the forward-scattered protons are measured in the Roman Pot system. Exclusivity of the event is guaranteed by requiring the transverse momentum balance of all four final-state particles. Differential cross sections are measured as functions of observables related to the central hadronic final state and to the forward-scattered protons. They are measured in a fiducial region corresponding to the acceptance of the STAR detector and determined by the central particles’ transverse momenta and pseudorapidities as well as by the forward-scattered protons’ momenta. This fiducial region roughly corresponds to the square of the four-momentum transfers at the proton vertices in the range 0.04 GeV2 < −t 1 , −t 2 < 0.2 GeV2, invariant masses of the charged particle pairs up to a few GeV and pseudorapidities of the centrally-produced hadrons in the range |η| < 0.7. The measured cross sections are compared to phenomenological predictions based on the Double Pomeron Exchange (DPE) model. Structures observed in the mass spectra of π + π − and K + K − pairs are consistent with the DPE model, while angular distributions of pions suggest a dominant spin-0 contribution to π + π − production. For π + π − production, the fiducial cross section is extrapolated to the Lorentz-invariant region, which allows decomposition of the invariant mass spectrum into continuum and resonant contributions. The extrapolated cross section is well described by the continuum production and at least three resonances, the f 0(980), f 2(1270) and f 0(1500), with a possible small contribution from the f 0(1370). Fits to the extrapolated differential cross section as a function of t 1 and t 2 enable extraction of the exponential slope parameters in several bins of the invariant mass of π + π − pairs. These parameters are sensitive to the size of the interaction region.

Published
2020
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2. Observation of D_{s}^{±}/D^{0} Enhancement in Au+Au Collisions at sqrt[s_{NN}]=200 GeV

Author

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, Barish, A, Behera, R, Bellwied, A, Bhasin, J, Bielcik, J, Bielcikova, L C, Bland, I G, Bordyuzhin, J D, Brandenburg, A V, Brandin, J, 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, J, Chen, J H, Chen, X, Chen, Z, Chen, J, Cheng, M, Cherney, M, Chevalier, S, Choudhury, W, Christie, X, Chu, H J, Crawford, M, Csanád, M, Daugherity, T G, Dedovich, 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, Fedorisin, C J, Feng, Y, Feng, P, Filip, E, Finch, Y, Fisyak, A, Francisco, C, Fu, L, Fulek, C A, Gagliardi, T, Galatyuk, F, Geurts, N, Ghimire, A, Gibson, K, Gopal, X, Gou, D, Grosnick, W, Guryn, A I, Hamad, A, Hamed, S, Harabasz, J W, Harris, S, He, W, He, X, He, Y, He, S, Heppelmann, N, Herrmann, E, Hoffman, L, Holub, Y, Hong, S, Horvat, Y, Hu, H Z, Huang, S L, Huang, T, Huang, X, Huang, T J, Humanic, P, Huo, G, Igo, D, Isenhower, W W, Jacobs, C, Jena, A, Jentsch, Y, Ji, J, Jia, K, Jiang, S, Jowzaee, X, Ju, E G, Judd, S, Kabana, M L, Kabir, S, Kagamaster, D, Kalinkin, K, Kang, D, Kapukchyan, K, Kauder, H W, Ke, D, Keane, A, Kechechyan, M, Kelsey, Y V, Khyzhniak, D P, Kikoła, C, Kim, B, Kimelman, D, Kincses, T A, Kinghorn, I, Kisel, A, Kiselev, M, Kocan, L, Kochenda, L K, Kosarzewski, L, Kramarik, P, Kravtsov, K, Krueger, N, Kulathunga Mudiyanselage, L, Kumar, S, Kumar, R, Kunnawalkam Elayavalli, J H, Kwasizur, R, Lacey, S, Lan, J M, Landgraf, J, Lauret, A, Lebedev, R, Lednicky, J H, Lee, Y H, Leung, C, Li, W, Li, X, Li, Y, Li, Y, Liang, R, Licenik, T, Lin, Y, Lin, M A, Lisa, F, Liu, H, Liu, P, Liu, T, Liu, X, Liu, Y, Liu, Z, Liu, T, Ljubicic, W J, Llope, R S, Longacre, N S, Lukow, S, Luo, X, Luo, G L, Ma, L, Ma, R, Ma, Y G, Ma, N, Magdy, R, Majka, D, Mallick, S, Margetis, C, Markert, H S, Matis, J A, Mazer, N G, Minaev, S, Mioduszewski, B, Mohanty, I, Mooney, Z, Moravcova, D A, Morozov, M, Nagy, J D, Nam, Md, Nasim, K, Nayak, D, Neff, J M, Nelson, D B, Nemes, M, Nie, G, Nigmatkulov, T, Niida, L V, Nogach, T, Nonaka, A S, Nunes, G, Odyniec, A, Ogawa, S, Oh, V A, Okorokov, B S, Page, R, Pak, A, Pandav, Y, Panebratsev, B, Pawlik, D, Pawlowska, H, Pei, C, Perkins, L, Pinsky, R L, Pintér, J, Pluta, B R, Pokhrel, J, Porter, M, Posik, N K, Pruthi, M, Przybycien, J, Putschke, H, Qiu, A, Quintero, S K, Radhakrishnan, S, Ramachandran, R L, Ray, R, Reed, H G, Ritter, O V, Rogachevskiy, J L, Romero, L, Ruan, J, Rusnak, N R, Sahoo, H, Sako, S, Salur, J, Sandweiss, S, Sato, W B, Schmidke, N, Schmitz, B R, Schweid, F, Seck, J, Seger, M, Sergeeva, R, Seto, P, Seyboth, N, Shah, E, Shahaliev, P V, Shanmuganathan, M, Shao, A I, Sheikh, W Q, Shen, S S, Shi, Y, Shi, Q Y, Shou, E P, Sichtermann, R, Sikora, M, Simko, J, Singh, S, Singha, N, Smirnov, W, Solyst, P, Sorensen, H M, Spinka, B, Srivastava, T D S, Stanislaus, M, Stefaniak, D J, Stewart, M, Strikhanov, B, Stringfellow, A A P, Suaide, M, Sumbera, B, Summa, X M, Sun, X, Sun, Y, Sun, B, Surrow, D N, Svirida, P, Szymanski, A H, Tang, Z, Tang, A, Taranenko, T, Tarnowsky, J H, Thomas, A R, Timmins, D, Tlusty, M, Tokarev, C A, Tomkiel, S, Trentalange, R E, Tribble, P, Tribedy, S K, Tripathy, O D, Tsai, Z, Tu, T, Ullrich, D G, Underwood, I, Upsal, G, Van Buren, J, Vanek, A N, Vasiliev, I, Vassiliev, F, Videbæk, S, Vokal, S A, Voloshin, F, Wang, G, Wang, J S, Wang, P, Wang, Y, Wang, Z, Wang, J C, Webb, P C, Weidenkaff, L, Wen, G D, Westfall, H, Wieman, S W, Wissink, R, Witt, Y, Wu, Z G, Xiao, G, Xie, W, Xie, H, Xu, N, Xu, Q H, Xu, Y F, Xu, Y, Xu, Z, Xu, C, Yang, Q, Yang, S, Yang, Y, Yang, Z, Yang, Z, Ye, L, Yi, K, Yip, Y, Yu, H, Zbroszczyk, W, Zha, C, Zhang, D, Zhang, S, Zhang, X P, Zhang, Y, Zhang, Z J, Zhang, Z, Zhang, J, Zhao, C, Zhong, C, Zhou, X, Zhu, Z, Zhu, M, Zurek, and M, Zyzak

Abstract

We report on the first measurement of charm-strange meson D_{s}^{±} production at midrapidity in Au+Au collisions at sqrt[s_{NN}]=200 GeV from the STAR experiment. The yield ratio between strange (D_{s}^{±}) and nonstrange (D^{0}) open-charm mesons is presented and compared to model calculations. A significant enhancement, relative to a pythia simulation of p+p collisions, is observed in the D_{s}^{±}/D^{0} yield ratio in Au+Au collisions over a large range of collision centralities. Model calculations incorporating abundant strange-quark production in the quark-gluon plasma and coalescence hadronization qualitatively reproduce the data. The transverse-momentum integrated yield ratio of D_{s}^{±}/D^{0} at midrapidity is consistent with a prediction from a statistical hadronization model with the parameters constrained by the yields of light and strange hadrons measured at the same collision energy. These results suggest that the coalescence of charm quarks with strange quarks in the quark-gluon plasma plays an important role in D_{s}^{±}-meson production in heavy-ion collisions.

Published
2021

3. Global Polarization of Ξ and Ω Hyperons in Au+Au Collisions at sqrt[s_{NN}]=200 GeV

Author

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, Barish, A, Behera, R, Bellwied, A, Bhasin, J, Bielcik, J, Bielcikova, L C, Bland, I G, Bordyuzhin, J D, Brandenburg, A V, Brandin, J, 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, J, Chen, J H, Chen, X, Chen, Z, Chen, J, Cheng, M, Cherney, M, Chevalier, S, Choudhury, W, Christie, X, Chu, H J, Crawford, M, Csanád, M, Daugherity, T G, Dedovich, 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, Fedorisin, C J, Feng, Y, Feng, P, Filip, E, Finch, Y, Fisyak, A, Francisco, L, Fulek, C A, Gagliardi, T, Galatyuk, F, Geurts, N, Ghimire, A, Gibson, K, Gopal, X, Gou, D, Grosnick, W, Guryn, A I, Hamad, A, Hamed, S, Harabasz, J W, Harris, S, He, W, He, X H, He, Y, He, S, Heppelmann, N, Herrmann, E, Hoffman, L, Holub, Y, Hong, S, Horvat, Y, Hu, H Z, Huang, S L, Huang, T, Huang, X, Huang, T J, Humanic, P, Huo, G, Igo, D, Isenhower, W W, Jacobs, C, Jena, A, Jentsch, Y, Ji, J, Jia, K, Jiang, S, Jowzaee, X, Ju, E G, Judd, S, Kabana, M L, Kabir, S, Kagamaster, D, Kalinkin, K, Kang, D, Kapukchyan, K, Kauder, H W, Ke, D, Keane, A, Kechechyan, M, Kelsey, Y V, Khyzhniak, D P, Kikoła, C, Kim, B, Kimelman, D, Kincses, T A, Kinghorn, I, Kisel, A, Kiselev, M, Kocan, L, Kochenda, L K, Kosarzewski, L, Kramarik, P, Kravtsov, K, Krueger, N, Kulathunga Mudiyanselage, L, Kumar, S, Kumar, R, Kunnawalkam Elayavalli, J H, Kwasizur, R, Lacey, S, Lan, J M, Landgraf, J, Lauret, A, Lebedev, R, Lednicky, J H, Lee, Y H, Leung, C, Li, W, Li, X, Li, Y, Li, Y, Liang, R, Licenik, T, Lin, Y, Lin, M A, Lisa, F, Liu, H, Liu, P, Liu, T, Liu, X, Liu, Y, Liu, Z, Liu, T, Ljubicic, W J, Llope, R S, Longacre, N S, Lukow, S, Luo, X, Luo, G L, Ma, L, Ma, R, Ma, Y G, Ma, N, Magdy, R, Majka, D, Mallick, S, Margetis, C, Markert, H S, Matis, J A, Mazer, N G, Minaev, S, Mioduszewski, B, Mohanty, I, Mooney, Z, Moravcova, D A, Morozov, M, Nagy, J D, Nam, Md, Nasim, K, Nayak, D, Neff, J M, Nelson, D B, Nemes, M, Nie, G, Nigmatkulov, T, Niida, L V, Nogach, T, Nonaka, A S, Nunes, G, Odyniec, A, Ogawa, S, Oh, V A, Okorokov, B S, Page, R, Pak, A, Pandav, Y, Panebratsev, B, Pawlik, D, Pawlowska, H, Pei, C, Perkins, L, Pinsky, R L, Pintér, J, Pluta, B R, Pokhrel, J, Porter, M, Posik, N K, Pruthi, M, Przybycien, J, Putschke, H, Qiu, A, Quintero, S K, Radhakrishnan, S, Ramachandran, R L, Ray, R, Reed, H G, Ritter, O V, Rogachevskiy, J L, Romero, L, Ruan, J, Rusnak, N R, Sahoo, H, Sako, S, Salur, J, Sandweiss, S, Sato, W B, Schmidke, N, Schmitz, B R, Schweid, F, Seck, J, Seger, M, Sergeeva, R, Seto, P, Seyboth, N, Shah, E, Shahaliev, P V, Shanmuganathan, M, Shao, A I, Sheikh, W Q, Shen, S S, Shi, Y, Shi, Q Y, Shou, E P, Sichtermann, R, Sikora, M, Simko, J, Singh, S, Singha, N, Smirnov, W, Solyst, P, Sorensen, H M, Spinka, B, Srivastava, T D S, Stanislaus, M, Stefaniak, D J, Stewart, M, Strikhanov, B, Stringfellow, A A P, Suaide, M, Sumbera, B, Summa, X M, Sun, X, Sun, Y, Sun, B, Surrow, D N, Svirida, P, Szymanski, A H, Tang, Z, Tang, A, Taranenko, T, Tarnowsky, J H, Thomas, A R, Timmins, D, Tlusty, M, Tokarev, C A, Tomkiel, S, Trentalange, R E, Tribble, P, Tribedy, S K, Tripathy, O D, Tsai, Z, Tu, T, Ullrich, D G, Underwood, I, Upsal, G, Van Buren, J, Vanek, A N, Vasiliev, I, Vassiliev, F, Videbæk, S, Vokal, S A, Voloshin, F, Wang, G, Wang, J S, Wang, P, Wang, Y, Wang, Z, Wang, J C, Webb, P C, Weidenkaff, L, Wen, G D, Westfall, H, Wieman, S W, Wissink, R, Witt, Y, Wu, Z G, Xiao, G, Xie, W, Xie, H, Xu, N, Xu, Q H, Xu, Y F, Xu, Y, Xu, Z, Xu, C, Yang, Q, Yang, S, Yang, Y, Yang, Z, Yang, Z, Ye, L, Yi, K, Yip, Y, Yu, H, Zbroszczyk, W, Zha, C, Zhang, D, Zhang, S, Zhang, X P, Zhang, Y, Zhang, Z J, Zhang, Z, Zhang, J, Zhao, C, Zhong, C, Zhou, X, Zhu, Z, Zhu, M, Zurek, and M, Zyzak

Abstract

Global polarization of Ξ and Ω hyperons has been measured for the first time in Au+Au collisions at sqrt[s_{NN}]=200 GeV. The measurements of the Ξ^{-} and Ξ[over ¯]^{+} hyperon polarization have been performed by two independent methods, via analysis of the angular distribution of the daughter particles in the parity violating weak decay Ξ→Λ+π, as well as by measuring the polarization of the daughter Λ hyperon, polarized via polarization transfer from its parent. The polarization, obtained by combining the results from the two methods and averaged over Ξ^{-} and Ξ[over ¯]^{+}, is measured to be ⟨P_{Ξ}⟩=0.47±0.10(stat)±0.23(syst)% for the collision centrality 20%-80%. The ⟨P_{Ξ}⟩ is found to be slightly larger than the inclusive Λ polarization and in reasonable agreement with a multiphase transport model. The ⟨P_{Ξ}⟩ is found to follow the centrality dependence of the vorticity predicted in the model, increasing toward more peripheral collisions. The global polarization of Ω, ⟨P_{Ω}⟩=1.11±0.87(stat)±1.97(syst)% was obtained by measuring the polarization of daughter Λ in the decay Ω→Λ+K, assuming the polarization transfer factor C_{ΩΛ}=1.

Published
2020

4. First Measurement of Λ_{c} Baryon Production in Au+Au Collisions at sqrt[s_{NN}]=200 GeV

Author

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, Barish, A, Behera, R, Bellwied, A, Bhasin, J, Bielcik, J, Bielcikova, L C, Bland, I G, Bordyuzhin, J D, Brandenburg, A V, Brandin, J, 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, J H, Chen, X, Chen, Z, Chen, J, Cheng, M, Cherney, M, Chevalier, S, Choudhury, W, Christie, H J, Crawford, M, Csanád, M, Daugherity, T G, Dedovich, I M, Deppner, A A, Derevschikov, L, Didenko, X, Dong, J L, Drachenberg, J C, Dunlop, T, Edmonds, N, Elsey, J, Engelage, G, Eppley, R, Esha, S, Esumi, O, Evdokimov, J, Ewigleben, O, Eyser, R, Fatemi, S, Fazio, P, Federic, J, Fedorisin, C J, Feng, Y, Feng, P, Filip, E, Finch, Y, Fisyak, A, Francisco, L, Fulek, C A, Gagliardi, T, Galatyuk, F, Geurts, A, Gibson, K, Gopal, D, Grosnick, W, Guryn, A I, Hamad, A, Hamed, J W, Harris, W, He, X, He, S, Heppelmann, N, Herrmann, E, Hoffman, L, Holub, Y, Hong, S, Horvat, Y, Hu, H Z, Huang, S L, Huang, T, Huang, X, Huang, T J, Humanic, P, Huo, G, Igo, D, Isenhower, W W, Jacobs, C, Jena, A, Jentsch, Y, Ji, J, Jia, K, Jiang, S, Jowzaee, X, Ju, E G, Judd, S, Kabana, M L, Kabir, S, Kagamaster, D, Kalinkin, K, Kang, D, Kapukchyan, K, Kauder, H W, Ke, D, Keane, A, Kechechyan, M, Kelsey, Y V, Khyzhniak, D P, Kikoła, C, Kim, B, Kimelman, D, Kincses, T A, Kinghorn, I, Kisel, A, Kiselev, A, Kisiel, M, Kocan, L, Kochenda, L K, Kosarzewski, L, Kramarik, P, Kravtsov, K, Krueger, N, Kulathunga Mudiyanselage, L, Kumar, R, Kunnawalkam Elayavalli, J H, Kwasizur, R, Lacey, S, Lan, J M, Landgraf, J, Lauret, A, Lebedev, R, Lednicky, J H, Lee, Y H, Leung, C, Li, W, Li, X, Li, Y, Li, Y, Liang, R, Licenik, T, Lin, Y, Lin, M A, Lisa, F, Liu, H, Liu, P, Liu, T, Liu, X, Liu, Y, Liu, Z, Liu, T, Ljubicic, W J, Llope, R S, Longacre, N S, Lukow, S, Luo, X, Luo, G L, Ma, L, Ma, R, Ma, Y G, Ma, N, Magdy, R, Majka, D, Mallick, S, Margetis, C, Markert, H S, Matis, J A, Mazer, N G, Minaev, S, Mioduszewski, B, Mohanty, I, Mooney, Z, Moravcova, D A, Morozov, M, Nagy, J D, Nam, Md, Nasim, K, Nayak, D, Neff, J M, Nelson, D B, Nemes, M, Nie, G, Nigmatkulov, T, Niida, L V, Nogach, T, Nonaka, G, Odyniec, A, Ogawa, S, Oh, V A, Okorokov, B S, Page, R, Pak, A, Pandav, Y, Panebratsev, B, Pawlik, D, Pawlowska, H, Pei, C, Perkins, L, Pinsky, R L, Pintér, J, Pluta, J, Porter, M, Posik, N K, Pruthi, M, Przybycien, J, Putschke, H, Qiu, A, Quintero, S K, Radhakrishnan, S, Ramachandran, R L, Ray, R, Reed, H G, Ritter, J B, Roberts, O V, Rogachevskiy, J L, Romero, L, Ruan, J, Rusnak, N R, Sahoo, H, Sako, S, Salur, J, Sandweiss, S, Sato, W B, Schmidke, N, Schmitz, B R, Schweid, F, Seck, J, Seger, M, Sergeeva, R, Seto, P, Seyboth, N, Shah, E, Shahaliev, P V, Shanmuganathan, M, Shao, F, Shen, W Q, Shen, S S, Shi, Q Y, Shou, E P, Sichtermann, R, Sikora, M, Simko, J, Singh, S, Singha, N, Smirnov, W, Solyst, P, Sorensen, H M, Spinka, B, Srivastava, T D S, Stanislaus, M, Stefaniak, D J, Stewart, M, Strikhanov, B, Stringfellow, A A P, Suaide, M, Sumbera, B, Summa, X M, Sun, Y, Sun, B, Surrow, D N, Svirida, P, Szymanski, A H, Tang, Z, Tang, A, Taranenko, T, Tarnowsky, J H, Thomas, A R, Timmins, D, Tlusty, M, Tokarev, C A, Tomkiel, S, Trentalange, R E, Tribble, P, Tribedy, S K, Tripathy, O D, Tsai, Z, Tu, T, Ullrich, D G, Underwood, I, Upsal, G, Van Buren, J, Vanek, A N, Vasiliev, I, Vassiliev, F, Videbæk, S, Vokal, S A, Voloshin, F, Wang, G, Wang, J S, Wang, P, Wang, Y, Wang, Z, Wang, J C, Webb, P C, Weidenkaff, L, Wen, G D, Westfall, H, Wieman, S W, Wissink, R, Witt, Y, Wu, Z G, Xiao, G, Xie, W, Xie, H, Xu, N, Xu, Q H, Xu, Y F, Xu, Y, Xu, Z, Xu, C, Yang, Q, Yang, S, Yang, Y, Yang, Z, Yang, Z, Ye, L, Yi, K, Yip, H, Zbroszczyk, W, Zha, D, Zhang, S, Zhang, X P, Zhang, Y, Zhang, Z J, Zhang, Z, Zhang, J, Zhao, C, Zhong, C, Zhou, X, Zhu, Z, Zhu, M, Zurek, and M, Zyzak

Abstract

We report on the first measurement of the charmed baryon Λ_{c}^{±} production at midrapidity (|y|1) in Au+Au collisions at sqrt[s_{NN}]=200 GeV collected by the STAR experiment at the Relativistic Heavy Ion Collider. The Λ_{c}/D^{0} [denoting (Λ_{c}^{+}+Λ_{c}^{-})/(D^{0}+D[over ¯]^{0})] yield ratio is measured to be 1.08±0.16 (stat)±0.26 (sys) in the 0%-20% most central Au+Au collisions for the transverse momentum (p_{T}) range 3p_{T}6 GeV/c. This is significantly larger than the pythia model calculations for p+p collisions. The measured Λ_{c}/D^{0} ratio, as a function of p_{T} and collision centrality, is comparable to the baryon-to-meson ratios for light and strange hadrons in Au+Au collisions. Model calculations including coalescence hadronization for charmed baryon and meson formation reproduce the features of our measured Λ_{c}/D^{0} ratio.

Published
2020

5. Non-monotonic energy dependence of net-proton number fluctuations

Author

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, Barish, A, Behera, R, Bellwied, A, Bhasin, J, Bielcik, J, Bielcikova, L C, Bland, I G, Bordyuzhin, J D, Brandenburg, A V, Brandin, J, 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, J, Chen, J H, Chen, X, Chen, Z, Chen, J, Cheng, M, Cherney, M, Chevalier, S, Choudhury, W, Christie, X, Chu, H J, Crawford, M, Csanád, M, Daugherity, T G, Dedovich, 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, Fedorisin, C J, Feng, Y, Feng, P, Filip, E, Finch, Y, Fisyak, A, Francisco, L, Fulek, C A, Gagliardi, T, Galatyuk, F, Geurts, A, Gibson, K, Gopal, X, Gou, D, Grosnick, W, Guryn, A I, Hamad, A, Hamed, S, Harabasz, J W, Harris, S, He, W, He, X H, He, Y, He, S, Heppelmann, N, Herrmann, E, Hoffman, L, Holub, Y, Hong, S, Horvat, Y, Hu, H Z, Huang, S L, Huang, T, Huang, X, Huang, T J, Humanic, P, Huo, G, Igo, D, Isenhower, W W, Jacobs, C, Jena, A, Jentsch, Y, Ji, J, Jia, K, Jiang, S, Jowzaee, X, Ju, E G, Judd, S, Kabana, M L, Kabir, S, Kagamaster, D, Kalinkin, K, Kang, D, Kapukchyan, K, Kauder, H W, Ke, D, Keane, A, Kechechyan, M, Kelsey, Y V, Khyzhniak, D P, Kikoła, C, Kim, B, Kimelman, D, Kincses, T A, Kinghorn, I, Kisel, A, Kiselev, M, Kocan, L, Kochenda, L K, Kosarzewski, L, Kramarik, P, Kravtsov, K, Krueger, N, Kulathunga Mudiyanselage, L, Kumar, S, Kumar, R, Kunnawalkam Elayavalli, J H, Kwasizur, R, Lacey, S, Lan, J M, Landgraf, J, Lauret, A, Lebedev, R, Lednicky, J H, Lee, Y H, Leung, C, Li, W, Li, X, Li, Y, Li, Y, Liang, R, Licenik, T, Lin, Y, Lin, M A, Lisa, F, Liu, H, Liu, P, Liu, T, Liu, X, Liu, Y, Liu, Z, Liu, T, Ljubicic, W J, Llope, R S, Longacre, N S, Lukow, S, Luo, X, Luo, G L, Ma, L, Ma, R, Ma, Y G, Ma, N, Magdy, R, Majka, D, Mallick, S, Margetis, C, Markert, H S, Matis, J A, Mazer, N G, Minaev, S, Mioduszewski, B, Mohanty, I, Mooney, Z, Moravcova, D A, Morozov, M, Nagy, J D, Nam, Md, Nasim, K, Nayak, D, Neff, J M, Nelson, D B, Nemes, M, Nie, G, Nigmatkulov, T, Niida, L V, Nogach, T, Nonaka, A S, Nunes, G, Odyniec, A, Ogawa, S, Oh, V A, Okorokov, B S, Page, R, Pak, A, Pandav, Y, Panebratsev, B, Pawlik, D, Pawlowska, H, Pei, C, Perkins, L, Pinsky, R L, Pintér, J, Pluta, J, Porter, M, Posik, N K, Pruthi, M, Przybycien, J, Putschke, H, Qiu, A, Quintero, S K, Radhakrishnan, S, Ramachandran, R L, Ray, R, Reed, H G, Ritter, O V, Rogachevskiy, J L, Romero, L, Ruan, J, Rusnak, N R, Sahoo, H, Sako, S, Salur, J, Sandweiss, S, Sato, W B, Schmidke, N, Schmitz, B R, Schweid, F, Seck, J, Seger, M, Sergeeva, R, Seto, P, Seyboth, N, Shah, E, Shahaliev, P V, Shanmuganathan, M, Shao, A I, Sheikh, W Q, Shen, S S, Shi, Y, Shi, Q Y, Shou, E P, Sichtermann, R, Sikora, M, Simko, J, Singh, S, Singha, N, Smirnov, W, Solyst, P, Sorensen, H M, Spinka, B, Srivastava, T D S, Stanislaus, M, Stefaniak, D J, Stewart, M, Strikhanov, B, Stringfellow, A A P, Suaide, M, Sumbera, B, Summa, X M, Sun, X, Sun, Y, Sun, B, Surrow, D N, Svirida, P, Szymanski, A H, Tang, Z, Tang, A, Taranenko, T, Tarnowsky, J H, Thomas, A R, Timmins, D, Tlusty, M, Tokarev, C A, Tomkiel, S, Trentalange, R E, Tribble, P, Tribedy, S K, Tripathy, O D, Tsai, Z, Tu, T, Ullrich, D G, Underwood, I, Upsal, G, Van Buren, J, Vanek, A N, Vasiliev, I, Vassiliev, F, Videbæk, S, Vokal, S A, Voloshin, F, Wang, G, Wang, J S, Wang, P, Wang, Y, Wang, Z, Wang, J C, Webb, P C, Weidenkaff, L, Wen, G D, Westfall, H, Wieman, S W, Wissink, R, Witt, Y, Wu, Z G, Xiao, G, Xie, W, Xie, H, Xu, N, Xu, Q H, Xu, Y F, Xu, Y, Xu, Z, Xu, C, Yang, Q, Yang, S, Yang, Y, Yang, Z, Yang, Z, Ye, L, Yi, K, Yip, Y, Yu, H, Zbroszczyk, W, Zha, C, Zhang, D, Zhang, S, Zhang, X P, Zhang, Y, Zhang, Z J, Zhang, Z, Zhang, J, Zhao, C, Zhong, C, Zhou, X, Zhu, Z, Zhu, M, Zurek, and M, Zyzak

Subjects
Physics, Quantum chromodynamics, Nuclear Theory, COLISÕES, General Physics and Astronomy, FOS: Physical sciences, Monotonic function, Function (mathematics), 01 natural sciences, High Energy Physics - Experiment, Nuclear physics, Nuclear Theory (nucl-th), High Energy Physics - Phenomenology, High Energy Physics - Experiment (hep-ex), High Energy Physics - Phenomenology (hep-ph), Critical point (thermodynamics), 0103 physical sciences, Kurtosis, Atomic number, Nuclear Experiment (nucl-ex), 010306 general physics, Relativistic Heavy Ion Collider, Nuclear Experiment, Energy (signal processing)
Abstract

Non-monotonic variation with collision energy ($\sqrt{s_{\rm NN}}$) of the moments of the net-baryon number distribution in heavy-ion collisions, related to the correlation length and the susceptibilities of the system, is suggested as a signature for the Quantum Chromodynamics (QCD) critical point. We report the first evidence of a non-monotonic variation in kurtosis times variance of the net-proton number (proxy for net-baryon number) distribution as a function of \rootsnn with 3.1$\sigma$ significance, for head-on (central) gold-on-gold (Au+Au) collisions measured using the STAR detector at RHIC. Data in non-central Au+Au collisions and models of heavy-ion collisions without a critical point show a monotonic variation as a function of $\sqrt{s_{\rm NN}}$., Comment: 12 Pages, 9 Figures and 5 Tables (published version)

Published
2020
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6. Polarization of Λ (Λ[over ¯]) Hyperons along the Beam Direction in Au+Au Collisions at sqrt[s_{NN}]=200 GeV

Author

J, Adam, L, Adamczyk, J R, Adams, J K, Adkins, G, Agakishiev, M M, Aggarwal, Z, Ahammed, I, Alekseev, D M, Anderson, R, Aoyama, A, Aparin, D, Arkhipkin, E C, Aschenauer, M U, Ashraf, F, Atetalla, A, Attri, G S, Averichev, V, Bairathi, K, Barish, A J, Bassill, A, Behera, R, Bellwied, A, Bhasin, A K, Bhati, J, Bielcik, J, Bielcikova, L C, Bland, I G, Bordyuzhin, J D, Brandenburg, A V, Brandin, J, Bryslawskyj, I, Bunzarov, J, 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, S, Chattopadhyay, J H, Chen, X, Chen, J, Cheng, M, Cherney, W, Christie, H J, Crawford, M, Csanád, S, Das, T G, Dedovich, I M, Deppner, A A, Derevschikov, L, Didenko, C, Dilks, X, Dong, J L, Drachenberg, J C, Dunlop, T, Edmonds, N, Elsey, J, Engelage, G, Eppley, R, Esha, S, Esumi, O, Evdokimov, J, Ewigleben, O, Eyser, R, Fatemi, S, Fazio, P, Federic, J, Fedorisin, Y, Feng, P, Filip, E, Finch, Y, Fisyak, L, Fulek, C A, Gagliardi, T, Galatyuk, F, Geurts, A, Gibson, K, Gopal, D, Grosnick, A, Gupta, W, Guryn, A I, Hamad, A, Hamed, J W, Harris, L, He, S, Heppelmann, N, Herrmann, L, Holub, Y, Hong, S, Horvat, B, Huang, H Z, Huang, S L, Huang, T, Huang, X, Huang, T J, Humanic, P, Huo, G, Igo, W W, Jacobs, C, Jena, A, Jentsch, Y, Ji, J, Jia, K, Jiang, S, Jowzaee, X, Ju, E G, Judd, S, Kabana, S, Kagamaster, D, Kalinkin, K, Kang, D, Kapukchyan, K, Kauder, H W, Ke, D, Keane, A, Kechechyan, M, Kelsey, Y V, Khyzhniak, D P, Kikoła, C, Kim, T A, Kinghorn, I, Kisel, A, Kisiel, M, Kocan, L, Kochenda, L K, Kosarzewski, L, Kramarik, P, Kravtsov, K, Krueger, N, Kulathunga Mudiyanselage, L, Kumar, R, Kunnawalkam Elayavalli, J H, Kwasizur, R, Lacey, J M, Landgraf, J, Lauret, A, Lebedev, R, Lednicky, J H, Lee, C, Li, W, Li, X, Li, Y, Li, Y, Liang, R, Licenik, T, Lin, A, Lipiec, M A, Lisa, F, Liu, H, Liu, P, Liu, T, Liu, X, Liu, Y, Liu, Z, Liu, T, Ljubicic, W J, Llope, M, Lomnitz, R S, Longacre, S, Luo, X, Luo, G L, Ma, L, Ma, R, Ma, Y G, Ma, N, Magdy Abdelwahab Abdelrahman, R, Majka, D, Mallick, S, Margetis, C, Markert, H S, Matis, O, Matonoha, J A, Mazer, K, Meehan, J C, Mei, N G, Minaev, S, Mioduszewski, D, Mishra, B, Mohanty, M M, Mondal, I, Mooney, Z, Moravcova, D A, Morozov, Md, Nasim, K, Nayak, J M, Nelson, D B, Nemes, M, Nie, G, Nigmatkulov, T, Niida, L V, Nogach, T, Nonaka, G, Odyniec, A, Ogawa, K, Oh, S, Oh, V A, Okorokov, B S, Page, R, Pak, Y, Panebratsev, B, Pawlik, D, Pawlowska, H, Pei, C, Perkins, R L, Pintér, J, Pluta, J, Porter, M, Posik, N K, Pruthi, M, Przybycien, J, Putschke, A, Quintero, S K, Radhakrishnan, S, Ramachandran, R L, Ray, R, Reed, H G, Ritter, J B, Roberts, O V, Rogachevskiy, J L, Romero, L, Ruan, J, Rusnak, O, Rusnakova, N R, Sahoo, P K, Sahu, S, Salur, J, Sandweiss, J, Schambach, W B, Schmidke, N, Schmitz, B R, Schweid, F, Seck, J, Seger, M, Sergeeva, R, Seto, P, Seyboth, N, Shah, E, Shahaliev, P V, Shanmuganathan, M, Shao, F, Shen, W Q, Shen, S S, Shi, Q Y, Shou, E P, Sichtermann, S, Siejka, R, Sikora, M, Simko, J, Singh, S, Singha, D, Smirnov, N, Smirnov, W, Solyst, P, Sorensen, H M, Spinka, B, Srivastava, T D S, Stanislaus, M, Stefaniak, D J, Stewart, M, Strikhanov, B, Stringfellow, A A P, Suaide, T, Sugiura, M, Sumbera, B, Summa, X M, Sun, Y, Sun, B, Surrow, D N, Svirida, P, Szymanski, A H, Tang, Z, Tang, A, Taranenko, T, Tarnowsky, J H, Thomas, A R, Timmins, D, Tlusty, T, Todoroki, M, Tokarev, C A, Tomkiel, S, Trentalange, R E, Tribble, P, Tribedy, S K, Tripathy, O D, Tsai, B, Tu, Z, Tu, T, Ullrich, D G, Underwood, I, Upsal, G, Van Buren, J, Vanek, A N, Vasiliev, I, Vassiliev, F, Videbæk, S, Vokal, S A, Voloshin, F, Wang, G, Wang, P, Wang, Y, Wang, J C, Webb, L, Wen, G D, Westfall, H, Wieman, S W, Wissink, R, Witt, Y, Wu, Z G, Xiao, G, Xie, W, Xie, H, Xu, N, Xu, Q H, Xu, Y F, Xu, Z, Xu, C, Yang, Q, Yang, S, Yang, Y, Yang, Z, Yang, Z, Ye, L, Yi, K, Yip, I-K, Yoo, H, Zbroszczyk, W, Zha, D, Zhang, L, Zhang, S, Zhang, X P, Zhang, Y, Zhang, Z, Zhang, J, Zhao, C, Zhong, C, Zhou, X, Zhu, Z, Zhu, M, Zurek, and M, Zyzak

Abstract

The Λ (Λ[over ¯]) hyperon polarization along the beam direction has been measured in Au+Au collisions at sqrt[s_{NN}]=200 GeV, for the first time in heavy-ion collisions. The polarization dependence on the hyperons' emission angle relative to the elliptic flow plane exhibits a second harmonic sine modulation, indicating a quadrupole pattern of the vorticity component along the beam direction, expected due to elliptic flow. The polarization is found to increase in more peripheral collisions, and shows no strong transverse momentum (p_{T}) dependence at p_{T} greater than 1 GeV/c. The magnitude of the signal is about 5 times smaller than those predicted by hydrodynamic and multiphase transport models; the observed phase of the emission angle dependence is also opposite to these model predictions. In contrast, the kinematic vorticity calculations in the blast-wave model tuned to reproduce particle spectra, elliptic flow, and the azimuthal dependence of the Gaussian source radii measured with the Hanbury Brown-Twiss intensity interferometry technique reproduce well the modulation phase measured in the data and capture the centrality and transverse momentum dependence of the polarization signal.

Published
2019

7. First Observation of the Directed Flow of D^{0} and D^{0}[over ¯] in Au+Au Collisions at sqrt[s_{NN}]=200 GeV

Author

J, Adam, L, Adamczyk, J R, Adams, J K, Adkins, G, Agakishiev, M M, Aggarwal, Z, Ahammed, I, Alekseev, D M, Anderson, R, Aoyama, A, Aparin, E C, Aschenauer, M U, Ashraf, F G, Atetalla, A, Attri, G S, Averichev, V, Bairathi, K, Barish, A J, Bassill, A, Behera, R, Bellwied, A, Bhasin, A K, Bhati, J, Bielcik, J, Bielcikova, L C, Bland, I G, Bordyuzhin, J D, Brandenburg, A V, Brandin, J, Bryslawskyj, I, Bunzarov, J, 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, S, Chattopadhyay, J H, Chen, X, Chen, J, Cheng, M, Cherney, W, Christie, G, Contin, H J, Crawford, M, Csanád, S, Das, T G, Dedovich, I M, Deppner, A A, Derevschikov, L, Didenko, C, Dilks, X, Dong, J L, Drachenberg, J C, Dunlop, T, Edmonds, N, Elsey, J, Engelage, G, Eppley, R, Esha, S, Esumi, O, Evdokimov, J, Ewigleben, O, Eyser, R, Fatemi, S, Fazio, P, Federic, J, Fedorisin, Y, Feng, P, Filip, E, Finch, Y, Fisyak, L, Fulek, C A, Gagliardi, T, Galatyuk, F, Geurts, A, Gibson, K, Gopal, L, Greiner, D, Grosnick, A, Gupta, W, Guryn, A I, Hamad, A, Hamed, J W, Harris, L, He, S, Heppelmann, N, Herrmann, L, Holub, Y, Hong, S, Horvat, B, Huang, H Z, Huang, S L, Huang, T, Huang, X, Huang, T J, Humanic, P, Huo, G, Igo, W W, Jacobs, C, Jena, A, Jentsch, Y, Ji, J, Jia, K, Jiang, S, Jowzaee, X, Ju, E G, Judd, S, Kabana, S, Kagamaster, D, Kalinkin, K, Kang, D, Kapukchyan, K, Kauder, H W, Ke, D, Keane, A, Kechechyan, M, Kelsey, Y V, Khyzhniak, D P, Kikoła, C, Kim, T A, Kinghorn, I, Kisel, A, Kisiel, M, Kocan, L, Kochenda, L K, Kosarzewski, L, Kramarik, P, Kravtsov, K, Krueger, N, Kulathunga Mudiyanselage, L, Kumar, R, Kunnawalkam Elayavalli, J H, Kwasizur, R, Lacey, J M, Landgraf, J, Lauret, A, Lebedev, R, Lednicky, J H, Lee, C, Li, W, Li, X, Li, Y, Li, Y, Liang, R, Licenik, T, Lin, A, Lipiec, M A, Lisa, F, Liu, H, Liu, P, Liu, T, Liu, X, Liu, Y, Liu, Z, Liu, T, Ljubicic, W J, Llope, M, Lomnitz, R S, Longacre, S, Luo, X, Luo, G L, Ma, L, Ma, R, Ma, Y G, Ma, N, Magdy, R, Majka, D, Mallick, S, Margetis, C, Markert, H S, Matis, O, Matonoha, J A, Mazer, K, Meehan, J C, Mei, N G, Minaev, S, Mioduszewski, D, Mishra, B, Mohanty, M M, Mondal, I, Mooney, Z, Moravcova, D A, Morozov, Md, Nasim, K, Nayak, J M, Nelson, D B, Nemes, M, Nie, G, Nigmatkulov, T, Niida, L V, Nogach, T, Nonaka, G, Odyniec, A, Ogawa, S, Oh, V A, Okorokov, B S, Page, R, Pak, Y, Panebratsev, B, Pawlik, D, Pawlowska, H, Pei, C, Perkins, R L, Pintér, J, Pluta, J, Porter, M, Posik, N K, Pruthi, M, Przybycien, J, Putschke, A, Quintero, S K, Radhakrishnan, S, Ramachandran, R L, Ray, R, Reed, H G, Ritter, J B, Roberts, O V, Rogachevskiy, J L, Romero, L, Ruan, J, Rusnak, O, Rusnakova, N R, Sahoo, P K, Sahu, S, Salur, J, Sandweiss, J, Schambach, W B, Schmidke, N, Schmitz, B R, Schweid, F, Seck, J, Seger, M, Sergeeva, R, Seto, P, Seyboth, N, Shah, E, Shahaliev, P V, Shanmuganathan, M, Shao, F, Shen, W Q, Shen, S S, Shi, Q Y, Shou, E P, Sichtermann, S, Siejka, R, Sikora, M, Simko, J, Singh, S, Singha, D, Smirnov, N, Smirnov, W, Solyst, P, Sorensen, H M, Spinka, B, Srivastava, T D S, Stanislaus, M, Stefaniak, D J, Stewart, M, Strikhanov, B, Stringfellow, A A P, Suaide, T, Sugiura, M, Sumbera, B, Summa, X M, Sun, Y, Sun, B, Surrow, D N, Svirida, M A, Szelezniak, P, Szymanski, A H, Tang, Z, Tang, A, Taranenko, T, Tarnowsky, A, Tawfik, J H, Thomas, A R, Timmins, D, Tlusty, M, Tokarev, C A, Tomkiel, S, Trentalange, R E, Tribble, P, Tribedy, S K, Tripathy, O D, Tsai, B, Tu, Z, Tu, T, Ullrich, D G, Underwood, I, Upsal, G, Van Buren, J, Vanek, A N, Vasiliev, I, Vassiliev, F, Videbæk, S, Vokal, S A, Voloshin, F, Wang, G, Wang, P, Wang, Y, Wang, J C, Webb, L, Wen, G D, Westfall, H, Wieman, S W, Wissink, R, Witt, Y, Wu, Z G, Xiao, G, Xie, W, Xie, H, Xu, N, Xu, Q H, Xu, Y F, Xu, Z, Xu, C, Yang, Q, Yang, S, Yang, Y, Yang, Z, Yang, Z, Ye, L, Yi, K, Yip, H, Zbroszczyk, W, Zha, D, Zhang, L, Zhang, S, Zhang, X P, Zhang, Y, Zhang, Z, Zhang, J, Zhao, C, Zhong, C, Zhou, X, Zhu, Z, Zhu, M, Zurek, and M, Zyzak

Abstract

We report the first measurement of rapidity-odd directed flow (v_{1}) for D^{0} and D^{0}[over ¯] mesons at midrapidity (|y|0.8) in Au+Au collisions at sqrt[s_{NN}]=200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 10-80% Au+Au collisions, the slope of the v_{1} rapidity dependence (dv_{1}/dy), averaged over D^{0} and D^{0}[over ¯] mesons, is -0.080±0.017(stat)±0.016(syst) for transverse momentum p_{T} above 1.5 GeV/c. The absolute value of D^{0} meson dv_{1}/dy is about 25 times larger than that for charged kaons, with 3.4σ significance. These data give a unique insight into the initial tilt of the produced matter, and offer constraints on the geometric and transport parameters of the hot QCD medium created in relativistic heavy-ion collisions.

Published
2019

8. Observation of Excess J/ψ Yield at Very Low Transverse Momenta in Au+Au Collisions at sqrt[s_{NN}]=200 GeV and U+U Collisions at sqrt[s_{NN}]=193 GeV

Author

J, Adam, L, Adamczyk, J R, Adams, J K, Adkins, G, Agakishiev, M M, Aggarwal, Z, Ahammed, I, Alekseev, D M, Anderson, R, Aoyama, A, Aparin, D, Arkhipkin, E C, Aschenauer, M U, Ashraf, F, Atetalla, A, Attri, G S, Averichev, V, Bairathi, K, Barish, A J, Bassill, A, Behera, R, Bellwied, A, Bhasin, A K, Bhati, J, Bielcik, J, Bielcikova, L C, Bland, I G, Bordyuzhin, J D, Brandenburg, A V, Brandin, J, Bryslawskyj, I, Bunzarov, J, 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, S, Chattopadhyay, J H, Chen, X, Chen, J, Cheng, M, Cherney, W, Christie, H J, Crawford, M, Csanad, S, Das, T G, Dedovich, I M, Deppner, A A, Derevschikov, L, Didenko, C, Dilks, X, Dong, J L, Drachenberg, J C, Dunlop, T, Edmonds, N, Elsey, J, Engelage, G, Eppley, R, Esha, S, Esumi, O, Evdokimov, J, Ewigleben, O, Eyser, R, Fatemi, S, Fazio, P, Federic, J, Fedorisin, Y, Feng, P, Filip, E, Finch, Y, Fisyak, L, Fulek, C A, Gagliardi, T, Galatyuk, F, Geurts, A, Gibson, D, Grosnick, A, Gupta, W, Guryn, A I, Hamad, A, Hamed, J W, Harris, L, He, S, Heppelmann, N, Herrmann, L, Holub, Y, Hong, S, Horvat, B, Huang, H Z, Huang, S L, Huang, T, Huang, X, Huang, T J, Humanic, P, Huo, G, Igo, W W, Jacobs, A, Jentsch, J, Jia, K, Jiang, S, Jowzaee, X, Ju, E G, Judd, S, Kabana, S, Kagamaster, D, Kalinkin, K, Kang, D, Kapukchyan, K, Kauder, H W, Ke, D, Keane, A, Kechechyan, M, Kelsey, D P, Kikoła, C, Kim, T A, Kinghorn, I, Kisel, A, Kisiel, M, Kocan, L, Kochenda, L K, Kosarzewski, L, Kramarik, P, Kravtsov, K, Krueger, N Kulathunga, Mudiyanselage, L, Kumar, R Kunnawalkam, Elayavalli, J H, Kwasizur, R, Lacey, J M, Landgraf, J, Lauret, A, Lebedev, R, Lednicky, J H, Lee, C, Li, W, Li, X, Li, Y, Li, Y, Liang, R, Licenik, T, Lin, A, Lipiec, M A, Lisa, F, Liu, H, Liu, P, Liu, X, Liu, Y, Liu, Z, Liu, T, Ljubicic, W J, Llope, M, Lomnitz, R S, Longacre, S, Luo, X, Luo, G L, Ma, L, Ma, R, Ma, Y G, Ma, N, Magdy, R, Majka, D, Mallick, S, Margetis, C, Markert, H S, Matis, O, Matonoha, J A, Mazer, K, Meehan, J C, Mei, N G, Minaev, S, Mioduszewski, D, Mishra, B, Mohanty, M M, Mondal, I, Mooney, Z, Moravcova, D A, Morozov, Md, Nasim, K, Nayak, J M, Nelson, D B, Nemes, M, Nie, G, Nigmatkulov, T, Niida, L V, Nogach, T, Nonaka, G, Odyniec, A, Ogawa, K, Oh, S, Oh, V A, Okorokov, B S, Page, R, Pak, Y, Panebratsev, B, Pawlik, H, Pei, C, Perkins, R L, Pinter, J, Pluta, J, Porter, M, Posik, N K, Pruthi, M, Przybycien, J, Putschke, A, Quintero, S K, Radhakrishnan, S, Ramachandran, R L, Ray, R, Reed, H G, Ritter, J B, Roberts, O V, Rogachevskiy, J L, Romero, L, Ruan, J, Rusnak, O, Rusnakova, N R, Sahoo, P K, Sahu, S, Salur, J, Sandweiss, J, Schambach, W B, Schmidke, N, Schmitz, B R, Schweid, F, Seck, J, Seger, M, Sergeeva, R, Seto, P, Seyboth, N, Shah, E, Shahaliev, P V, Shanmuganathan, M, Shao, F, Shen, W Q, Shen, S S, Shi, Q Y, Shou, E P, Sichtermann, S, Siejka, R, Sikora, M, Simko, JSingh, S, Singha, D, Smirnov, N, Smirnov, W, Solyst, P, Sorensen, H M, Spinka, B, Srivastava, T D S, Stanislaus, D J, Stewart, M, Strikhanov, B, Stringfellow, A A P, Suaide, T, Sugiura, M, Sumbera, B, Summa, X M, Sun, Y, Sun, B, Surrow, D N, Svirida, P, Szymanski, A H, Tang, Z, Tang, A, Taranenko, T, Tarnowsky, J H, Thomas, A R, Timmins, T, Todoroki, M, Tokarev, C A, Tomkiel, S, Trentalange, R E, Tribble, P, Tribedy, S K, Tripathy, O D, Tsai, B, Tu, T, Ullrich, D G, Underwood, I, Upsal, G, Van Buren, J, Vanek, A N, Vasiliev, I, Vassiliev, F, Videbæk, S, Vokal, S A, Voloshin, F, Wang, G, Wang, P, Wang, Y, Wang, J C, Webb, L, Wen, G D, Westfall, H, Wieman, S W, Wissink, R, Witt, Y, Wu, Z G, Xiao, G, Xie, W, Xie, H, Xu, N, Xu, Q H, Xu, Y F, Xu, Z, Xu, C, Yang, Q, Yang, S, Yang, Y, Yang, Z, Ye, L, Yi, K, Yip, I-K, Yoo, H, Zbroszczyk, W, Zha, D, Zhang, L, Zhang, S, Zhang, X P, Zhang, Y, Zhang, Z, Zhang, J, Zhao, C, Zhong, C, Zhou, X, Zhu, Z, Zhu, M K, Zurek, and M, Zyzak

Abstract

We report on the first measurements of J/ψ production at very low transverse momentum (p_{T}0.2 GeV/c) in hadronic Au+Au collisions at sqrt[s_{NN}]=200 GeV and U+U collisions at sqrt[s_{NN}]=193 GeV. Remarkably, the inferred nuclear modification factor of J/ψ at midrapidity in Au+Au (U+U) collisions reaches about 24 (52) for p_{T}0.05 GeV/c in the 60%-80% collision centrality class. This noteworthy enhancement cannot be explained by hadronic production accompanied by cold and hot medium effects. In addition, the dN/dt distribution of J/ψ for the very low p_{T} range is presented for the first time. The distribution is consistent with that expected from the Au nucleus and shows a hint of interference. Comparison of the measurements to theoretical calculations of coherent production shows that the excess yield can be described reasonably well and reveals a partial disruption of coherent production in semicentral collisions, perhaps due to the violent hadronic interactions. Incorporating theoretical calculations, the results strongly suggest that the dramatic enhancement of J/ψ yield observed at extremely low p_{T} originates from coherent photon-nucleus interactions. In particular, coherently produced J/ψ's in violent hadronic collisions may provide a novel probe of the quark-gluon plasma.

Published
2019

9. Measurement of away-side broadening with self-subtraction of flow in Au+Au collisions at GeV *

Author

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. Barish, A. Behera, R. Bellwied, A. Bhasin, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. D. Brandenburg, A. V. Brandin, J. 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, J. H. Chen, X. Chen, Z. Chen, J. Cheng, M. Cherney, M. Chevalier, S. Choudhury, W. Christie, X. Chu, H. J. Crawford, M. Csanád, M. Daugherity, T. G. Dedovich, 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. Fedorisin, C. J. Feng, Y. Feng, P. Filip, E. Finch, Y. Fisyak, A. Francisco, L. Fulek, C. A. Gagliardi, T. Galatyuk, F. Geurts, A. Gibson, K. Gopal, D. Grosnick, W. Guryn, A. I. Hamad, A. Hamed, S. Harabasz, J. W. Harris, S. He, W. He, X. H. He, S. Heppelmann, N. Herrmann, E. Hoffman, L. Holub, Y. Hong, S. Horvat, Y. Hu, H. Z. Huang, S. L. Huang, T. Huang, X. Huang, T. J. Humanic, P. Huo, G. Igo, D. Isenhower, W. W. Jacobs, C. Jena, A. Jentsch, Y. JI, J. Jia, K. Jiang, S. Jowzaee, X. Ju, E. G. Judd, S. Kabana, M. L. Kabir, S. Kagamaster, D. Kalinkin, K. Kang, D. Kapukchyan, K. Kauder, H. W. Ke, D. Keane, A. Kechechyan, M. Kelsey, Y. V. Khyzhniak, D. P. Kikoła, C. Kim, B. Kimelman, D. Kincses, T. A. Kinghorn, I. Kisel, A. Kiselev, M. Kocan, L. Kochenda, L. K. Kosarzewski, L. Kramarik, P. Kravtsov, K. Krueger, N. Kulathunga Mudiyanselage, L. Kumar, S. Kumar, R. Kunnawalkam Elayavalli, J. H. Kwasizur, R. Lacey, S. Lan, J. M. Landgraf, J. Lauret, A. Lebedev, R. Lednicky, J. H. Lee, Y. H. Leung, C. Li, W. Li, X. Li, Y. Li, Y. Liang, R. Licenik, T. Lin, Y. Lin, M. A. Lisa, F. Liu, H. Liu, P. Liu, T. Liu, X. Liu, Y. Liu, Z. Liu, T. Ljubicic, W. J. Llope, R. S. Longacre, N. S. Lukow, S. Luo, X. Luo, G. L. Ma, L. Ma, R. Ma, Y. G. Ma, N. Magdy, R. Majka, D. Mallick, S. Margetis, C. Markert, H. S. Matis, J. A. Mazer, N. G. Minaev, S. Mioduszewski, B. Mohanty, I. Mooney, Z. Moravcova, D. A. Morozov, M. Nagy, J. D. Nam, Nasim Md., K. Nayak, D. Neff, J. M. Nelson, D. B. Nemes, M. Nie, G. Nigmatkulov, T. Niida, L. V. Nogach, T. Nonaka, A. S. Nunes, G. Odyniec, A. Ogawa, S. Oh, V. A. Okorokov, B. S. Page, R. Pak, A. Pandav, Y. Panebratsev, B. Pawlik, D. Pawlowska, H. Pei, C. Perkins, L. Pinsky, R. L. Pintér, J. Pluta, J. Porter, M. Posik, N. K. Pruthi, M. Przybycien, J. Putschke, H. Qiu, A. Quintero, S. K. Radhakrishnan, S. Ramachandran, R. L. Ray, R. Reed, H. G. Ritter, O. V. Rogachevskiy, J. L. Romero, L. Ruan, J. Rusnak, N. R. Sahoo, H. Sako, S. Salur, J. Sandweiss, S. Sato, W. B. Schmidke, N. Schmitz, B. R. Schweid, F. Seck, J. Seger, M. Sergeeva, R. Seto, P. Seyboth, N. Shah, E. Shahaliev, P. V. Shanmuganathan, M. Shao, A. I. Sheikh, F. Shen, W. Q. Shen, S. S. Shi, Q. Y. Shou, E. P. Sichtermann, R. Sikora, M. Simko, J. Singh, S. Singha, N. Smirnov, W. Solyst, P. Sorensen, H. M. Spinka, B. Srivastava, T. D. S. Stanislaus, M. Stefaniak, D. J. Stewart, M. Strikhanov, B. Stringfellow, A. A. P. Suaide, M. Sumbera, B. Summa, X. M. Sun, X. Sun, Y. Sun, B. Surrow, D. N. Svirida, P. Szymanski, A. H. Tang, Z. Tang, A. Taranenko, T. Tarnowsky, J. H. Thomas, A. R. Timmins, D. Tlusty, M. Tokarev, C. A. Tomkiel, S. Trentalange, R. E. Tribble, P. Tribedy, S. K. Tripathy, O. D. Tsai, Z. Tu, T. Ullrich, D. G. Underwood, I. Upsal, G. Van Buren, J. Vanek, A. N. Vasiliev, I. Vassiliev, F. Videbæk, S. Vokal, S. A. Voloshin, F. Wang, G. Wang, J. S. Wang, P. Wang, Y. Wang, Z. Wang, J. C. Webb, P. C. Weidenkaff, L. Wen, G. D. Westfall, H. Wieman, S. W. Wissink, R. Witt, Y. Wu, Z. G. Xiao, G. Xie, W. Xie, H. Xu, N. Xu, Q. H. Xu, Y. F. Xu, Y. Xu, Z. Xu, C. Yang, Q. Yang, S. Yang, Y. Yang, Z. Yang, Z. Ye, L. Yi, K. Yip, H. Zbroszczyk, W. Zha, C. Zhang, D. Zhang, S. Zhang, X. P. Zhang, Y. Zhang, Z. J. Zhang, Z. Zhang, J. Zhao, C. Zhong, C. Zhou, X. Zhu, Z. Zhu, M. Zurek, and M. Zyzak

Subjects
Physics, Nuclear and High Energy Physics, Energy loss, 010308 nuclear & particles physics, Subtraction, Astronomy and Astrophysics, Parton, 01 natural sciences, Nuclear physics, Pseudorapidity, 0103 physical sciences, Transverse momentum, Heavy ion, 010306 general physics, Anisotropy, Instrumentation
Abstract

High transverse momentum ( ) particle production is suppressed owing to the parton (jet) energy loss in the hot dense medium created in relativistic heavy-ion collisions. Redistribution of energy at low-to-modest has been difficult to measure, owing to large anisotropic backgrounds. We report a data-driven method for background evaluation and subtraction, exploiting the away-side pseudorapidity gaps, to measure the jetlike correlation shape in Au+Au collisions at GeV in the STAR experiment. The correlation shapes, for trigger particles and various associated particle ranges within , are consistent with Gaussians, and their widths increase with centrality. The results indicate jet broadening in the medium created in central heavy-ion collisions.

Published
2020
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10. Low-p_{T} e^{+}e^{-} Pair Production in Au+Au Collisions at sqrt[s_{NN}]=200 GeV and U+U Collisions at sqrt[s_{NN}]=193 GeV at STAR

Author

J, Adam, L, Adamczyk, J R, Adams, J K, Adkins, G, Agakishiev, M M, Aggarwal, Z, Ahammed, N N, Ajitanand, I, Alekseev, D M, Anderson, R, Aoyama, A, Aparin, D, Arkhipkin, E C, Aschenauer, M U, Ashraf, F, Atetalla, A, Attri, G S, Averichev, X, Bai, V, Bairathi, K, Barish, A J, Bassill, A, Behera, R, Bellwied, A, Bhasin, A K, Bhati, J, Bielcik, J, Bielcikova, L C, Bland, I G, Bordyuzhin, J D, Brandenburg, A V, Brandin, D, Brown, J, Bryslawskyj, I, Bunzarov, J, Butterworth, H, Caines, M, Calderón de la Barca Sánchez, J M, Campbell, D, Cebra, I, Chakaberia, P, Chaloupka, F-H, Chang, Z, Chang, N, Chankova-Bunzarova, A, Chatterjee, S, Chattopadhyay, J H, Chen, X, Chen, J, Cheng, M, Cherney, W, Christie, G, Contin, H J, Crawford, S, Das, T G, Dedovich, I M, Deppner, A A, Derevschikov, L, Didenko, C, Dilks, X, Dong, J L, Drachenberg, J C, Dunlop, L G, Efimov, N, Elsey, J, Engelage, G, Eppley, R, Esha, S, Esumi, O, Evdokimov, J, Ewigleben, O, Eyser, R, Fatemi, S, Fazio, P, Federic, P, Federicova, J, Fedorisin, P, Filip, E, Finch, Y, Fisyak, C E, Flores, L, Fulek, C A, Gagliardi, T, Galatyuk, F, Geurts, A, Gibson, D, Grosnick, D S, Gunarathne, Y, Guo, A, Gupta, W, Guryn, A I, Hamad, A, Hamed, A, Harlenderova, J W, Harris, L, He, S, Heppelmann, N, Herrmann, A, Hirsch, L, Holub, S, Horvat, X, Huang, B, Huang, S L, Huang, H Z, Huang, T, Huang, T J, Humanic, P, Huo, G, Igo, W W, Jacobs, A, Jentsch, J, Jia, K, Jiang, S, Jowzaee, E G, Judd, S, Kabana, D, Kalinkin, K, Kang, D, Kapukchyan, K, Kauder, H W, Ke, D, Keane, A, Kechechyan, D P, Kikoła, C, Kim, T A, Kinghorn, I, Kisel, A, Kisiel, S R, Klein, L, Kochenda, L K, Kosarzewski, A F, Kraishan, L, Kramarik, L, Krauth, P, Kravtsov, K, Krueger, N, Kulathunga, S, Kumar, L, Kumar, J, Kvapil, J H, Kwasizur, R, Lacey, J M, Landgraf, J, Lauret, A, Lebedev, R, Lednicky, J H, Lee, X, Li, C, Li, W, Li, Y, Li, Y, Liang, J, Lidrych, T, Lin, A, Lipiec, M A, Lisa, F, Liu, P, Liu, H, Liu, Y, Liu, T, Ljubicic, W J, Llope, M, Lomnitz, R S, Longacre, X, Luo, S, Luo, G L, Ma, Y G, Ma, L, Ma, R, Ma, N, Magdy, R, Majka, D, Mallick, S, Margetis, C, Markert, H S, Matis, O, Matonoha, D, Mayes, J A, Mazer, K, Meehan, J C, Mei, N G, Minaev, S, Mioduszewski, D, Mishra, B, Mohanty, M M, Mondal, I, Mooney, D A, Morozov, Md, Nasim, J D, Negrete, J M, Nelson, D B, Nemes, M, Nie, G, Nigmatkulov, T, Niida, L V, Nogach, T, Nonaka, S B, Nurushev, G, Odyniec, A, Ogawa, K, Oh, S, Oh, V A, Okorokov, D, Olvitt, B S, Page, R, Pak, Y, Panebratsev, B, Pawlik, H, Pei, C, Perkins, J, Pluta, J, Porter, M, Posik, N K, Pruthi, M, Przybycien, J, Putschke, A, Quintero, S K, Radhakrishnan, S, Ramachandran, R L, Ray, R, Reed, H G, Ritter, J B, Roberts, O V, Rogachevskiy, J L, Romero, L, Ruan, J, Rusnak, O, Rusnakova, N R, Sahoo, P K, Sahu, S, Salur, J, Sandweiss, J, Schambach, A M, Schmah, W B, Schmidke, N, Schmitz, B R, Schweid, F, Seck, J, Seger, M, Sergeeva, R, Seto, P, Seyboth, N, Shah, E, Shahaliev, P V, Shanmuganathan, M, Shao, W Q, Shen, F, Shen, S S, Shi, Q Y, Shou, E P, Sichtermann, S, Siejka, R, Sikora, M, Simko, S, Singha, N, Smirnov, D, Smirnov, W, Solyst, P, Sorensen, H M, Spinka, B, Srivastava, T D S, Stanislaus, D J, Stewart, M, Strikhanov, B, Stringfellow, A A P, Suaide, T, Sugiura, M, Sumbera, B, Summa, Y, Sun, X, Sun, X M, Sun, B, Surrow, D N, Svirida, P, Szymanski, Z, Tang, A H, Tang, A, Taranenko, T, Tarnowsky, J H, Thomas, A R, Timmins, D, Tlusty, T, Todoroki, M, Tokarev, C A, Tomkiel, S, Trentalange, R E, Tribble, P, Tribedy, S K, Tripathy, O D, Tsai, B, Tu, T, Ullrich, D G, Underwood, I, Upsal, G, Van Buren, J, Vanek, A N, Vasiliev, I, Vassiliev, F, Videbæk, S, Vokal, S A, Voloshin, A, Vossen, G, Wang, Y, Wang, F, Wang, J C, Webb, L, Wen, G D, Westfall, H, Wieman, S W, Wissink, R, Witt, Y, Wu, Z G, Xiao, G, Xie, W, Xie, Q H, Xu, Z, Xu, J, Xu, Y F, Xu, N, Xu, S, Yang, C, Yang, Q, Yang, Y, Yang, Z, Ye, L, Yi, K, Yip, I-K, Yoo, N, Yu, H, Zbroszczyk, W, Zha, Z, Zhang, L, Zhang, Y, Zhang, X P, Zhang, J, Zhang, S, Zhang, J, Zhao, C, Zhong, C, Zhou, L, Zhou, Z, Zhu, X, Zhu, and M, Zyzak

Abstract

We report first measurements of e^{+}e^{-} pair production in the mass region 0.4M_{ee}2.6 GeV/c^{2} at low transverse momentum (p_{T}0.15 GeV/c) in noncentral Au+Au collisions at sqrt[s_{NN}]=200 GeV and U+U collisions at sqrt[s_{NN}]=193 GeV. Significant enhancement factors, expressed as ratios of data over known hadronic contributions, are observed in the 40%-80% centrality of these collisions. The excess yields peak distinctly at low p_{T} with a width (sqrt[⟨p_{T}^{2}⟩]) between 40 and 60 MeV/c. The absolute cross section of the excess depends weakly on centrality, while those from a theoretical model calculation incorporating an in-medium broadened ρ spectral function and radiation from a quark gluon plasma or hadronic cocktail contributions increase dramatically with an increasing number of participant nucleons. Model calculations of photon-photon interactions generated by the initial projectile and target nuclei describe the observed excess yields but fail to reproduce the p_{T}^{2} distributions.

Published
2018

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