Elliptic flow of electrons from heavy-flavor hadron decays in Au+Au collisions at sNN=\sqrt{s_{\rm NN}} = 200, 62.4, and 39 GeV

We present measurements of elliptic flow ($v_2$) of electrons from the decays of heavy-flavor hadrons ($e_{HF}$) by the STAR experiment. For Au+Au collisions at $\sqrt{s_{\rm NN}} =$ 200 GeV we report $v_2$, for transverse momentum ($p_T$) between 0.2 and 7 GeV/c using three methods: the event plane method ($v_{2}${EP}), two-particle correlations ($v_2${2}), and four-particle correlations ($v_2${4}). For Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 62.4 and 39 GeV we report $v_2${2} for $p_T< 2$ GeV/c. $v_2${2} and $v_2${4} are non-zero at low and intermediate $p_T$ at 200 GeV, and $v_2${2} is consistent with zero at low $p_T$ at other energies. The $v_2${2} at the two lower beam energies is systematically lower than at $\sqrt{s_{\rm NN}} =$ 200 GeV for $p_T < 1$ GeV/c. This difference may suggest that charm quarks interact less strongly with the surrounding nuclear matter at those two lower energies compared to $\sqrt{s_{\rm NN}} = 200$ GeV.Comment: Version accepted by PR

Investigation of K+K−K^+K^- pairs in the effective mass region near 2mK2m_K

The DIRAC experiment at CERN investigated in the reaction $\rm{p}(24~\rm{GeV}/c) + Ni$ the particle pairs $K^+K^-, \pi^+ \pi^-$ and $p \bar{p}$ with relative momentum $Q$ in the pair system less than 100 MeV/c. Because of background influence studies, DIRAC explored three subsamples of $K^+K^-$ pairs, obtained by subtracting -- using time-of-flight (TOF) technique -- background from initial $Q$ distributions with $K^+K^-$ sample fractions more than 70\%, 50\% and 30\%. The corresponding pair distributions in $Q$ and in its longitudinal projection $Q_L$ were analyzed first in a Coulomb model, which takes into account only Coulomb final state interaction (FSI) and assuming point-like pair production. This Coulomb model analysis leads to a $K^+K^-$ yield increase of about four at $Q_L=0.5$ MeV/c compared to 100 MeV/c. In order to study contributions from strong interaction, a second more sophisticated model was applied, considering besides Coulomb FSI also strong FSI via the resonances $f_0(980)$ and $a_0(980)$ and a variable distance $r^*$ between the produced $K$ mesons. This analysis was based on three different parameter sets for the pair production. For the 70\% subsample and with best parameters, $3680\pm 370$ $K^+K^-$ pairs was found to be compared to $3900\pm 410$ $K^+K^-$ extracted by means of the Coulomb model. Knowing the efficiency of the TOF cut for background suppression, the total number of detected $K^+K^-$ pairs was evaluated to be around $40000\pm 10\%$, which agrees with the result from the 30\% subsample. The $K^+K^-$ pair number in the 50\% subsample differs from the two other values by about three standard deviations, confirming -- as discussed in the paper -- that experimental data in this subsample is less reliable

J/ψ production cross section and its dependence on charged-particle multiplicity in p + p collisions at s=200 GeV

We present a measurement of inclusive J/ψ production at mid-rapidity (|y|&lt;1) in p+p collisions at a center-of-mass energy of s=200 GeV with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The differential production cross section for J/ψ as a function of transverse momentum (p ) for

J/\u3c8 production cross section and its dependence on charged-particle multiplicity in p\u202f+\u202fp collisions at s=200 GeV

We present a measurement of inclusive J/\u3c8 production at mid-rapidity ( |y|<1 ) in p+p collisions at a center-of-mass energy of s=200 GeV with the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The differential production cross section for J/\u3c8 as a function of transverse momentum ( pT ) for 0<pT<14 GeV/c and the total cross section are reported and compared to calculations from the color evaporation model and the non-relativistic Quantum Chromodynamics model. The dependence of J/\u3c8 relative yields in three pT intervals on charged-particle multiplicity at mid-rapidity is measured for the first time in p+p collisions at s=200 GeV and compared with that measured at s=7 TeV, PYTHIA8 and EPOS3 Monte Carlo generators, and the Percolation model prediction

Improved measurement of the longitudinal spin transfer to \u39b and \u39b hyperons in polarized proton-proton collisions at s =200 GeV

The longitudinal spin transfer DLL to \u39b and \u39b\uaf hyperons produced in high-energy polarized proton--proton collisions is expected to be sensitive to the helicity distribution functions of strange quarks and anti-quarks of the proton, and to longitudinally polarized fragmentation functions. We report an improved measurement of DLL from data obtained at a center-of-mass energy of s 1a = 200 GeV with the STAR detector at RHIC. The data have an approximately twelve times larger figure-of-merit than prior results and cover |\u3b7|< 1.2 in pseudo-rapidity with transverse momenta pT up to 6 GeV/c. In the forward scattering hemisphere at largest pT, the longitudinal spin transfer is found to be DLL = -0.036 \ub1 0.048 (stat) \ub1 0.013(sys) for \u39b hyperons and DLL = 0.032 \ub1 0.043\,(stat) \ub1 0.013\,(sys) for \u39b\uaf anti-hyperons. The dependences on \u3b7 and pT are presented and compared with model evaluations

Beam-Energy Dependence of Directed Flow of \u39b, \u39b , K\ub1, Ks0, and \u3c6 in Au+Au Collisions

Rapidity-odd directed-flow measurements at midrapidity are presented for \u39b, \u39b\uaf, K\ub1, Ks0, and \u3d5 at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV in Au+Au collisions recorded by the Solenoidal Tracker detector at the Relativistic Heavy Ion Collider. These measurements greatly expand the scope of data available to constrain models with differing prescriptions for the equation of state of quantum chromodynamics. Results show good sensitivity for testing a picture where flow is assumed to be imposed before hadron formation and the observed particles are assumed to form via coalescence of constituent quarks. The pattern of departure from a coalescence-inspired sum rule can be a valuable new tool for probing the collision dynamics

Correlation measurements between flow harmonics in Au+Au collisions at RHIC

354Flow harmonics ( vn ) in the Fourier expansion of the azimuthal distribution of particles are widely used to quantify the anisotropy in particle emission in high-energy heavy-ion collisions. The symmetric cumulants, SC(m,n) , are used to measure the correlations between different orders of flow harmonics. These correlations are used to constrain the initial conditions and the transport properties of the medium in theoretical models. In this Letter, we present the first measurements of the four-particle symmetric cumulants in Au+Au collisions at sNN=39 and 200 GeV from data collected by the STAR experiment at RHIC. We observe that v2 and v3 are anti-correlated in all centrality intervals with similar correlation strengths from 39 GeV Au+Au to 2.76 TeV Pb+Pb (measured by the ALICE experiment). The v2 – v4 correlation seems to be stronger at 39 GeV than at higher collision energies. The initial-stage anti-correlations between second and third order eccentricities are sufficient to describe the measured correlations between v2 and v3 . The best description of v2 – v4 correlations at sNN=200GeV is obtained with inclusion of the system's nonlinear response to initial eccentricities accompanied by the viscous effect with η/s>0.08 . Theoretical calculations using different initial conditions, equations of state and viscous coefficients need to be further explored to extract η/s of the medium created at RHIC.openopenAdam, J.; Adamczyk, L.; Adams, J.R.; Adkins, J.K.; Agakishiev, G.; Aggarwal, M.M.; Ahammed, Z.; Ajitanand, N.N.; Alekseev, I.; Anderson, D.M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E.C.; Ashraf, M.U.; Atetalla, F.; Attri, A.; Averichev, G.S.; Bai, X.; Bairathi, V.; Barish, K.; Bassill, A.J.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A.K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L.C.; Bordyuzhin, I.G.; Bouchet, J.; Brandenburg, J.D.; Brandin, A.V.; Brown, D.; Bryslawskyj, J.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J.M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, F.-H.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, J.H.; Chen, X.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H.J.; Das, S.; Dedovich, T.G.; Deppner, I.M.; Derevschikov, A.A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J.L.; Dunlop, J.C.; Efimov, L.G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C.E.; Fulek, L.; Gagliardi, C.A.; Geurts, F.; Gibson, A.; Grosnick, D.; Gunarathne, D.S.; Guo, Y.; Gupta, A.; Guryn, W.; Hamad, A.I.; Hamed, A.; Harlenderova, A.; Harris, J.W.; He, L.; Heppelmann, S.; Heppelmann, S.; Herrmann, N.; Hirsch, A.; Holub, L.; Horvat, S.; Huang, X.; Huang, B.; Huang, S.L.; Huang, T.; Huang, H.Z.; Humanic, T.J.; Huo, P.; Igo, G.; Jacobs, W.W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E.G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kapukchyan, D.; Kauder, K.; Ke, H.W.; Keane, D.; Kechechyan, A.; Kikoła, D.P.; Kim, C.; Kinghorn, T.A.; Kisel, I.; Kisiel, A.; Kochenda, L.; Kosarzewski, L.K.; Kraishan, A.F.; Kramarik, L.; Krauth, L.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, S.; Kumar, L.; Kvapil, J.; Kwasizur, J.H.; Lacey, R.; Landgraf, J.M.; Landry, K.D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J.H.; Li, Y.; Li, W.; Li, X.; Li, C.; Lidrych, J.; Lin, T.; Lisa, M.A.; Liu, Y.; Liu, H.; Liu, F.; Liu, P.; Ljubicic, T.; Llope, W.J.; Lomnitz, M.; Longacre, R.S.; Luo, S.; Luo, X.; Ma, R.; Ma, Y.G.; Ma, G.L.; Ma, L.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H.S.; Matonoha, O.; Mayes, D.; Mazer, J.A.; Meehan, K.; Mei, J.C.; Minaev, N.G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M.M.; Mooney, I.; Morozov, D.A.; Mustafa, M.K.; Nasim, Md.; Nayak, T.K.; Negrete, J.D.; Nelson, J.M.; Nemes, D.B.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L.V.; Nonaka, T.; Nurushev, S.B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V.A.; Olvitt, D.; Page, B.S.; Pak, R.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Pruthi, N.K.; Przybycien, M.; Putschke, J.; Quintero, A.; Radhakrishnan, S.K.; Ramachandran, S.; Ray, R.L.; Reed, R.; Ritter, H.G.; Roberts, J.B.; Rogachevskiy, O.V.; Romero, J.L.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N.R.; Sahu, P.K.; Salur, S.; Sandweiss, J.; Schambach, J.; Schmah, A.M.; Schmidke, W.B.; Schmitz, N.; Schweid, B.R.; Seger, J.; Sergeeva, M.; Seto, R.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P.V.; Shao, M.; Shen, W.Q.; Shen, F.; Shi, Z.; Shi, S.S.; Shou, Q.Y.; Sichtermann, E.P.; Sikora, R.; Simko, M.; Singha, S.; Smirnov, D.; Smirnov, N.; Solyst, W.; Sorensen, P.; Spinka, H.M.; Srivastava, B.; Stanislaus, T.D.S.; Stewart, D.J.; Strikhanov, M.; Stringfellow, B.; Suaide, A.A.P.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, X.M.; Sun, X.; Sun, Y.; Surrow, B.; Svirida, D.N.; Tang, A.H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Thäder, J.; Thomas, J.H.; Timmins, A.R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; TomKiel, C.A.; Trentalange, S.; Tribble, R.E.; Tribedy, P.; Tripathy, S.K.; Trzeciak, B.A.; Tsai, O.D.; Tu, B.; Ullrich, T.; Underwood, D.G.; Upsal, I.; Van Buren, G.; Vanek, J.; Vasiliev, A.N.; Vassiliev, I.; Videbæk, F.; Vokal, S.; Voloshin, S.A.; Vossen, A.; Wang, F.; Wang, G.; Wang, Y.; Wang, Y.; Webb, J.C.; Webb, G.; Wen, L.; Westfall, G.D.; Wieman, H.; Wissink, S.W.; Witt, R.; Wu, Y.; Xiao, Z.G.; Xie, W.; Xie, G.; Xu, Z.; Xu, J.; Xu, Q.H.; Xu, Y.F.; Xu, N.; Yang, C.; Yang, S.; Yang, Q.; Yang, Y.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I.-K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, J.B.; Zhang, X.P.; Zhang, S.; Zhang, Z.; Zhang, L.; Zhang, J.; Zhang, J.; Zhang, Y.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, C.; Zhou, L.; Zhu, Z.; Zhu, X.; Zyzak, M.Adam, J.; Adamczyk, L.; Adams, J. R.; Adkins, J. K.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Ajitanand, N. N.; Alekseev, I.; Anderson, D. M.; Aoyama, R.; Aparin, A.; Arkhipkin, D.; Aschenauer, E. C.; Ashraf, M. U.; Atetalla, F.; Attri, A.; Averichev, G. S.; Bai, X.; Bairathi, V.; Barish, K.; Bassill, A. J.; Behera, A.; Bellwied, R.; Bhasin, A.; Bhati, A. K.; Bhattarai, P.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Bouchet, J.; Brandenburg, J. D.; Brandin, A. V.; Brown, D.; Bryslawskyj, J.; Bunzarov, I.; Butterworth, J.; Caines, H.; Calderón de la Barca Sánchez, M.; Campbell, J. M.; Cebra, D.; Chakaberia, I.; Chaloupka, P.; Chang, F. -H.; Chang, Z.; Chankova-Bunzarova, N.; Chatterjee, A.; Chattopadhyay, S.; Chen, J. H.; Chen, X.; Chen, X.; Cheng, J.; Cherney, M.; Christie, W.; Contin, G.; Crawford, H. J.; Das, S.; Dedovich, T. G.; Deppner, I. M.; Derevschikov, A. A.; Didenko, L.; Dilks, C.; Dong, X.; Drachenberg, J. L.; Dunlop, J. C.; Efimov, L. G.; Elsey, N.; Engelage, J.; Eppley, G.; Esha, R.; Esumi, S.; Evdokimov, O.; Ewigleben, J.; Eyser, O.; Fatemi, R.; Fazio, S.; Federic, P.; Federicova, P.; Fedorisin, J.; Feng, Z.; Filip, P.; Finch, E.; Fisyak, Y.; Flores, C. E.; Fulek, L.; Gagliardi, C. A.; Geurts, F.; Gibson, A.; Grosnick, D.; Gunarathne, D. S.; Guo, Y.; Gupta, A.; Guryn, W.; Hamad, A. I.; Hamed, A.; Harlenderova, A.; Harris, J. W.; He, L.; Heppelmann, S.; Heppelmann, S.; Herrmann, N.; Hirsch, A.; Holub, L.; Horvat, S.; Huang, X.; Huang, B.; Huang, S. L.; Huang, T.; Huang, H. Z.; Humanic, T. J.; Huo, P.; Igo, G.; Jacobs, W. W.; Jentsch, A.; Jia, J.; Jiang, K.; Jowzaee, S.; Judd, E. G.; Kabana, S.; Kalinkin, D.; Kang, K.; Kapukchyan, D.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Kikoła, D. P.; Kim, C.; Kinghorn, T. A.; Kisel, I.; Kisiel, A.; Kochenda, L.; Kosarzewski, L. K.; Kraishan, A. F.; Kramarik, L.; Krauth, L.; Kravtsov, P.; Krueger, K.; Kulathunga, N.; Kumar, S.; Kumar, L.; Kvapil, J.; Kwasizur, J. H.; Lacey, R.; Landgraf, J. M.; Landry, K. D.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Li, Y.; Li, W.; Li, X.; Li, C.; Lidrych, J.; Lin, T.; Lisa, M. A.; Liu, Y.; Liu, H.; Liu, F.; Liu, P.; Ljubicic, T.; Llope, W. J.; Lomnitz, M.; Longacre, R. S.; Luo, S.; Luo, X.; Ma, R.; Ma, Y. G.; Ma, G. L.; Ma, L.; Magdy, N.; Majka, R.; Mallick, D.; Margetis, S.; Markert, C.; Matis, H. S.; Matonoha, O.; Mayes, D.; Mazer, J. A.; Meehan, K.; Mei, J. C.; Minaev, N. G.; Mioduszewski, S.; Mishra, D.; Mizuno, S.; Mohanty, B.; Mondal, M. M.; Mooney, I.; Morozov, D. A.; Mustafa, M. K.; Nasim, Md.; Nayak, T. K.; Negrete, J. D.; Nelson, J. M.; Nemes, D. B.; Nie, M.; Nigmatkulov, G.; Niida, T.; Nogach, L. V.; Nonaka, T.; Nurushev, S. B.; Odyniec, G.; Ogawa, A.; Oh, K.; Okorokov, V. A.; Olvitt, D.; Page, B. S.; Pak, R.; Panebratsev, Y.; Pawlik, B.; Pei, H.; Perkins, C.; Pluta, J.; Poniatowska, K.; Porter, J.; Posik, M.; Pruthi, N. K.; Przybycien, M.; Putschke, J.; Quintero, A.; Radhakrishnan, S. K.; Ramachandran, S.; Ray, R. L.; Reed, R.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ruan, L.; Rusnak, J.; Rusnakova, O.; Sahoo, N. R.; Sahu, P. K.; Salur, S.; Sandweiss, J.; Schambach, J.; Schmah, A. M.; Schmidke, W. B.; Schmitz, N.; Schweid, B. R.; Seger, J.; Sergeeva, M.; Seto, R.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shanmuganathan, P. V.; Shao, M.; Shen, W. Q.; Shen, F.; Shi, Z.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Sikora, R.; Simko, M.; Singha, S.; Smirnov, D.; Smirnov, N.; Solyst, W.; Sorensen, P.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Stewart, D. J.; Strikhanov, M.; Stringfellow, B.; Suaide, A. A. P.; Sugiura, T.; Sumbera, M.; Summa, B.; Sun, X. M.; Sun, X.; Sun, Y.; Surrow, B.; Svirida, D. N.; Tang, A. H.; Tang, Z.; Taranenko, A.; Tarnowsky, T.; Thäder, J.; Thomas, J. H.; Timmins, A. R.; Tlusty, D.; Todoroki, T.; Tokarev, M.; Tomkiel, C. A.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Tripathy, S. K.; Trzeciak, B. A.; Tsai, O. D.; Tu, B.; Ullrich, T.; Underwood, D. G.; Upsal, I.; Van Buren, G.; Vanek, J.; Vasiliev, A. N.; Vassiliev, I.; Videbæk, F.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wang, F.; Wang, G.; Wang, Y.; Wang, Y.; Webb, J. C.; Webb, G.; Wen, L.; Westfall, G. D.; Wieman, H.; Wissink, S. W.; Witt, R.; Wu, Y.; Xiao, Z. G.; Xie, W.; Xie, G.; Xu, Z.; Xu, J.; Xu, Q. H.; Xu, Y. F.; Xu, N.; Yang, C.; Yang, S.; Yang, Q.; Yang, Y.; Ye, Z.; Yi, L.; Yip, K.; Yoo, I. -K.; Yu, N.; Zbroszczyk, H.; Zha, W.; Zhang, J. B.; Zhang, X. P.; Zhang, S.; Zhang, Z.; Zhang, L.; Zhang, J.; Zhang, J.; Zhang, Y.; Zhang, S.; Zhao, J.; Zhong, C.; Zhou, C.; Zhou, L.; Zhu, Z.; Zhu, X.; Zyzak, M

Direct virtual photon production in Au+Au collisions atsNN=200\ua0GeV

We report the direct virtual photon invariant yields in the transverse momentum ranges 16 GeV/c the production follows TAA scaling. Model calculations with contributions from thermal radiation and initial hard parton scattering are consistent within uncertainties with the direct virtual photon invariant yield