Single Spin Asymmetry ANA_N in Polarized Proton-Proton Elastic Scattering at s=200\sqrt{s}=200 GeV

We report a high precision measurement of the transverse single spin asymmetry $A_N$ at the center of mass energy $\sqrt{s}=200$ GeV in elastic proton-proton scattering by the STAR experiment at RHIC. The $A_N$ was measured in the four-momentum transfer squared $t$ range $0.003 \leqslant |t| \leqslant 0.035$ \GeVcSq, the region of a significant interference between the electromagnetic and hadronic scattering amplitudes. The measured values of $A_N$ and its $t$-dependence are consistent with a vanishing hadronic spin-flip amplitude, thus providing strong constraints on the ratio of the single spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated by the Pomeron amplitude at this $\sqrt{s}$, we conclude that this measurement addresses the question about the presence of a hadronic spin flip due to the Pomeron exchange in polarized proton-proton elastic scattering.Comment: 12 pages, 6 figure

Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV

We report a measurement of the longitudinal double-spin asymmetry A_LL and the differential cross section for inclusive Pi0 production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV. The cross section was measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be in good agreement with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T < 11 GeV/c and excludes a maximal positive gluon polarization in the proton. The mean transverse momentum fraction of Pi0's in their parent jets was found to be around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC

High pTp_{T} non-photonic electron production in pp+pp collisions at s\sqrt{s} = 200 GeV

We present the measurement of non-photonic electron production at high transverse momentum ($p_T >$ 2.5 GeV/$c$) in $p$ + $p$ collisions at $\sqrt{s}$ = 200 GeV using data recorded during 2005 and 2008 by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The measured cross-sections from the two runs are consistent with each other despite a large difference in photonic background levels due to different detector configurations. We compare the measured non-photonic electron cross-sections with previously published RHIC data and pQCD calculations. Using the relative contributions of B and D mesons to non-photonic electrons, we determine the integrated cross sections of electrons ($\frac{e^++e^-}{2}$) at 3 GeV/$c < p_T <~$10 GeV/$c$ from bottom and charm meson decays to be ${d\sigma_{(B\to e)+(B\to D \to e)} \over dy_e}|_{y_e=0}$ = 4.0$\pm0.5$({\rm stat.})$\pm1.1$({\rm syst.}) nb and ${d\sigma_{D\to e} \over dy_e}|_{y_e=0}$ = 6.2$\pm0.7$({\rm stat.})$\pm1.5$({\rm syst.}) nb, respectively.Comment: 17 pages, 17 figure

Evolution of the differential transverse momentum correlation function with centrality in Au+Au collisions at sNN=200\sqrt{s_{NN}} = 200 GeV

We present first measurements of the evolution of the differential transverse momentum correlation function, {\it C}, with collision centrality in Au+Au interactions at $\sqrt{s_{NN}} = 200$ GeV. {\it C} exhibits a strong dependence on collision centrality that is qualitatively similar to that of number correlations previously reported. We use the observed longitudinal broadening of the near-side peak of {\it C} with increasing centrality to estimate the ratio of the shear viscosity to entropy density, $\eta/s$, of the matter formed in central Au+Au interactions. We obtain an upper limit estimate of $\eta/s$ that suggests that the produced medium has a small viscosity per unit entropy.Comment: 7 pages, 4 figures, STAR paper published in Phys. Lett.

Longitudinal scaling property of the charge balance function in Au + Au collisions at 200 GeV

We present measurements of the charge balance function, from the charged particles, for diverse pseudorapidity and transverse momentum ranges in Au + Au collisions at 200 GeV using the STAR detector at RHIC. We observe that the balance function is boost-invariant within the pseudorapidity coverage [-1.3, 1.3]. The balance function properly scaled by the width of the observed pseudorapidity window does not depend on the position or size of the pseudorapidity window. This scaling property also holds for particles in different transverse momentum ranges. In addition, we find that the width of the balance function decreases monotonically with increasing transverse momentum for all centrality classes.Comment: 6 pages, 3 figure

Measurement of the Bottom contribution to non-photonic electron production in p+pp+p collisions at s\sqrt{s} =200 GeV

The contribution of $B$ meson decays to non-photonic electrons, which are mainly produced by the semi-leptonic decays of heavy flavor mesons, in $p+p$ collisions at $\sqrt{s} =$ 200 GeV has been measured using azimuthal correlations between non-photonic electrons and hadrons. The extracted $B$ decay contribution is approximately 50% at a transverse momentum of $p_{T} \geq 5$ GeV/$c$. These measurements constrain the nuclear modification factor for electrons from $B$ and $D$ meson decays. The result indicates that $B$ meson production in heavy ion collisions is also suppressed at high $p_{T}$.Comment: 6 pages, 4 figures, accepted by PR

J/ψ polarization in p+p collisions at s=200 GeV in STAR

AbstractWe report on a polarization measurement of inclusive J/ψ mesons in the di-electron decay channel at mid-rapidity at 2<pT<6 GeV/c in p+p collisions at s=200 GeV. Data were taken with the STAR detector at RHIC. The J/ψ polarization measurement should help to distinguish between different models of the J/ψ production mechanism since they predict different pT dependences of the J/ψ polarization. In this analysis, J/ψ polarization is studied in the helicity frame. The polarization parameter λθ measured at RHIC becomes smaller towards high pT, indicating more longitudinal J/ψ polarization as pT increases. The result is compared with predictions of presently available models

Dielectron Azimuthal Anisotropy At Mid-rapidity In Au+au Collisions At Snn =200 Gev

We report on the first measurement of the azimuthal anisotropy (v2) of dielectrons (e+e- pairs) at mid-rapidity from sNN=200 GeV Au+Au collisions with the STAR detector at the Relativistic Heavy Ion Collider (RHIC), presented as a function of transverse momentum (pT) for different invariant-mass regions. In the mass region Mee<1.1 GeV/c2 the dielectron v2 measurements are found to be consistent with expectations from π0,η,ω, and φ decay contributions. In the mass region 1.1<Mee<2.9GeV/c2, the measured dielectron v2 is consistent, within experimental uncertainties, with that from the cc¯ contributions.906Adams, J., (2005) Nucl. Phys. A, 757, p. 102. , NUPABL 0375-9474Arsene, I., (2005) Nucl. Phys. A, 757, p. 1. , NUPABL 0375-9474Adcox, K., (2005) Nucl. Phys. A, 757, p. 184. , NUPABL 0375-9474Back, B.B., (2005) Nucl. Phys. A, 757, p. 28. , NUPABL 0375-9474Rapp, R., Wambach, J., (2002) Adv. Nucl. Phys., 25, p. 1. , 0065-2970David, G., Rapp, R., Xu, Z., (2008) Phys. Rep., 462, p. 176. , PRPLCM 0370-1573Agakichiev, G., (2005) Eur. Phys. J. C, 41, p. 475. , EPCFFB 1434-6044Arnaldi, R., (2006) Phys. Rev. Lett., 96, p. 162302. , PRLTAO 0031-9007Brown, G.E., Rho, M., (1996) Phys. Rep., 269, p. 333. , PRPLCM 0370-1573Rapp, R., Wambach, J., (1999) Eur. Phys. J. A, 6, p. 415. , EPJAFV 1434-6001Dusling, K., Teaney, D., Zahed, I., (2007) Phys. Rev. C, 75, p. 024908. , PRVCAN 0556-2813Van Hees, H., Rapp, R., (2008) Nucl. Phys. A, 806, p. 339. , NUPABL 0375-9474Renk, T., Ruppert, J., (2008) Phys. Rev. C, 77, p. 024907. , PRVCAN 0556-2813Adare, A., (2010) Phys. Rev. C, 81, p. 034911. , PRVCAN 0556-2813Adamczyk, L., (2014) Phys. Rev. Lett., 113, p. 022301. , a longer version (unpublished). PRLTAO 0031-9007Rapp, R., Wambach, J., Van Hees, H., (2010) Relativistic Heavy-Ion Physics, , in, edited by R. Stock, Landolt Börnstein New Series I/23A (Springer, Berlin), Chap. 4-1Linnyk, O., Cassing, W., Manninen, J., Bratkovskaya, E.L., Ko, C.M., (2012) Phys. Rev. C, 85, p. 024910. , PRVCAN 0556-2813Xu, J.-H., Chen, H.F., Dong, X., Wang, Q., Zhang, Y.F., (2012) Phys. Rev. C, 85, p. 024906. , PRVCAN 0556-2813Adare, A., (2010) Phys. Rev. Lett., 104, p. 132301. , PRLTAO 0031-9007Poskanzer, A.M., Voloshin, S.A., (1998) Phys. Rev. C, 58, p. 1671. , PRVCAN 0556-2813Adare, A., (2012) Phys. Rev. Lett., 109, p. 122302. , PRLTAO 0031-9007Van Hees, H., Gale, C., Rapp, R., (2011) Phys. Rev. C, 84, p. 054906. , PRVCAN 0556-2813Chatterjee, R., Srivastava, D.K., Heinz, U., Gale, C., (2007) Phys. Rev. C, 75, p. 054909. , PRVCAN 0556-2813Adare, A., (2009) Phys. Lett. B, 670, p. 313. , PYLBAJ 0370-2693Bonner, B., (2003) Nucl. Instrum. Methods A, 508, p. 181. , NIMAER 0168-9002Shao, M., (2002) Nucl. Instrum. Methods A, 492, p. 344Wu, J., (2005) Nucl. Instrum. Methods A, 538, p. 243. , NIMAER 0168-9002Landgraf, J.M., (2003) Nucl. Instrum. Methods A, 499, p. 762. , NIMAER 0168-9002Ackermann, K.H., (2003) Nucl. Instrum. Methods A, 499, p. 624. , NIMAER 0168-9002Anderson, M., (2003) Nucl. Instrum. Methods A, 499, p. 659. , NIMAER 0168-9002Bichsel, H., (2006) Nucl. Instrum. Methods A, 562, p. 154. , NIMAER 0168-9002Xu, Y., (2010) Nucl. Instrum. Methods A, 614, p. 28. , NIMAER 0168-9002Shao, M., (2006) Nucl. Instrum. Methods A, 558, p. 419. , NIMAER 0168-9002Adams, J., (2005) Phys. Lett. B, 616, p. 8. , PYLBAJ 0370-2693Ruan, L., Ph.D. thesis, University of Science and Technology of China, 2005, arXiv:nucl-ex/0503018 (unpublished)Llope, W.J., (2004) Nucl. Instrum. Methods A, 522, p. 252. , NIMAER 0168-9002Adler, C., (2002) Phys. Rev. Lett., 89, p. 202301. , PRLTAO 0031-9007Adams, J., (2005) Phys. Rev. Lett., 94, p. 062301. , PRLTAO 0031-9007Adamczyk, L., (2012) Phys. Rev. C, 86, p. 024906. , PRVCAN 0556-2813Zhao, J., (2013), https://drupal.star.bnl.gov/STAR/theses/phd-32, Ph.D. thesis, Shanghai Institute of Applied Physics, (unpublished)Voloshin, S.A., Poskanzer, A.M., Snellings, R., (2010) Relativistic Heavy Ion Physics, pp. 5-54. , in, Landolt-Börnstein Vol. 1/23 (Springer-Verlag, Berlin), ppAdamczyk, L., (2013) Phys. Rev. C, 88, p. 014902. , PRVCAN 0556-2813Abelev, B.I., (2008) Phys. Rev. C, 77, p. 054901. , PRVCAN 0556-2813Abelev, B.I., (2006) Phys. Rev. Lett., 97, p. 152301. , PRLTAO 0031-9007Abelev, B.I., (2009) Phys. Rev. C, 79, p. 034909. , PRVCAN 0556-2813Abelev, B.I., (2009) Phys. Rev. C, 79, p. 064903. , PRVCAN 0556-2813Adams, J., (2005) Phys. Lett. B, 612, p. 181. , PYLBAJ 0370-2693Adler, S.S., (2007) Phys. Rev. C, 75, p. 024909. , PRVCAN 0556-2813Tang, Z., Xu, Y., Ruan, L., Van Buren, G., Wang, F., Xu, Z., (2009) Phys. Rev. C, 79, p. 051901. , (R) () PRVCAN 0556-2813Shao, M., Yi, L., Tang, Z., Chen, H., Li, C., Xu, Z., (2010) J. Phys. G, 37, p. 085104. , JPGPED 0954-3899Afanasiev, S., (2009) Phys. Rev. C, 80, p. 054907. , PRVCAN 0556-2813Adams, J., (2005) Phys. Rev. C, 72, p. 014904. , PRVCAN 0556-2813Abelev, B.I., (2007) Phys. Rev. Lett., 99, p. 112301. , PRLTAO 0031-9007Kroll, N.M., Wada, W., (1955) Phys. Rev., 98, p. 1355. , PHRVAO 0031-899XRuan, L., (2011) Nucl. Phys. A, 855, p. 269. , NUPABL 0375-9474Huang, B., (2011), Ph.D. thesis, University of Science and Technology of China, (unpublished)Sjöstrand, T., (2001) Comput. Phys. Commun., 135, p. 238. , CPHCBZ 0010-4655Adamczyk, L., (2012) Phys. Rev. D, 86, p. 072013. , PRVDAQ 1550-7998Agakishiev, H., (2011) Phys. Rev. D, 83, p. 052006. , PRVDAQ 1550-7998Adare, A., (2011) Phys. Rev. C, 84, p. 044905. , PRVCAN 0556-2813Adare, A., (2012) Phys. Rev. C, 85, p. 064914. , PRVCAN 0556-2813Adare, A., (2007) Phys. Rev. Lett., 98, p. 162301. , PRLTAO 0031-9007Adams, J., (2004) Phys. Rev. Lett., 92, p. 052302. , PRLTAO 0031-9007Vujanovic, G., Young, C., Schenke, B., Jeon, S., Rapp, R., Gale, C., (2013) Nucl. Phys. A, 904-905, p. 557c. , NUPABL 0375-9474Vujanovic, G., Young, C., Schenke, B., Jeon, S., Rapp, R., Gale, C., (2014) Phys. Rev. C, 89, p. 034904. , PRVCAN 0556-281