High transverse momentum inclusive neutral pion production in d+Au collisions at RHIC

Preliminary results are presented on high-pT inclusive neutral pion production in d+Au collisions at sqrt(sNN) = 200 GeV in the pseudo-rapidity range 0 gamma,gamma are detected in the Barrel electromagnetic calorimeter of the STAR experiment at RHIC. The analysis procedure is described in detail and the results are found to be in good agreement with earlier STAR findings and with next-to-leading order perturbative QCD calculations.Comment: 4 pages, 3 figures, poster proceedings of Quark Matter conference, Budapest (Hungary), 4-9 August 200

Strangelet search at RHIC

Two position sensitive Shower Maximum Detector (SMDs) for Zero-Degree Calorimeters (ZDCs) were installed by STAR before run 2004 at both upstream and downstream from the interaction point along the beam axis where particles with small rigidity are swept away by strong magnetic field. The ZDC-SMDs provides information about neutral energy deposition as a function of transverse position in ZDCs. We report the preliminary results of strangelet search from a triggered data-set sampling 100 million Au+Au collisions at top RHIC energy.Comment: Strange Quark Matter 2004 conference proceedin

Azimuthal anisotropy of K0s and Lambda prduction at mid-rapidity from Au+Au collisions at root s = 130 GeV

We report STAR results on the azimuthal anisotropy parameter v2 for strange particles K0S, L and Lbar at midrapidity in Au+Au collisions at sNN = 130 GeV at RHIC. The value of v2 as a function of transverse momentum of the produced particles pt and collision centrality is presented for both particles up to pt 3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2 measurement is compared with hydrodynamic model calculations. The physics implications of the pt integrated v2 magnitude as a function of particle mass are also discussed.Comment: 6 pages, 4 figures, by the STAR collaboratio

Azimuthal anisotropy of K0S and Lambda + Lambda -bar production at midrapidity from Au+Au collisions at sqrt[sNN]=130 GeV

We report STAR results on the azimuthal anisotropy parameter v2 for strange particles K0S, Lambda , and Lambda -bar at midrapidity in Au+Au collisions at sqrt[sNN]=130 GeV at the Relativistic Heavy Ion Collider. The value of v2 as a function of transverse momentum, pt, of the produced particle and collision centrality is presented for both particles up to pt~3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2 measurement is compared with hydrodynamic model calculations. The physics implications of the pt integrated v2 magnitude as a function of particle mass are also discussed.Alle Autoren: C. Adler, Z. Ahammed, C. Allgower, J. Amonett, B. D. Anderson, M. Anderson, G. S. Averichev, J. Balewski, O. Barannikova, L. S. Barnby, J. Baudot, S. Bekele, V. V. Belaga, R. Bellwied, J. Berger, H. Bichsel, A. Billmeier, L. C. Bland, C. O. Blyth, B. E. Bonner, A. Boucham, A. Brandin, A. Bravar, R. V. Cadman, H. Caines, M. Calderón de la Barca Sánchez, A. Cardenas, J. Carroll, J. Castillo, M. Castro, D. Cebra, P. Chaloupka, S. Chattopadhyay, Y. Chen, S. P. Chernenko, M. Cherney, A. Chikanian, B. Choi, W. Christie, J. P. Coffin, T. M. Cormier, J. G. Cramer, H. J. Crawford, W. S. Deng, A. A. Derevschikov, L. Didenko, T. Dietel, J. E. Draper, V. B. Dunin, J. C. Dunlop, V. Eckardt, L. G. Efimov, V. Emelianov, J. Engelage, G. Eppley, B. Erazmus, P. Fachini, V. Faine, K. Filimonov, E. Finch, Y. Fisyak, D. Flierl, K. J. Foley, J. Fu, C. A. Gagliardi, N. Gagunashvili, J. Gans, L. Gaudichet, M. Germain, F. Geurts, V. Ghazikhanian, O. Grachov, V. Grigoriev, M. Guedon, E. Gushin, T. J. Hallman, D. Hardtke, J. W. Harris, T. W. Henry, S. Heppelmann, T. Herston, B. Hippolyte, A. Hirsch, E. Hjort, G. W. Hoffmann, M. Horsley, H. Z. Huang, T. J. Humanic, G. Igo, A. Ishihara, Yu. I. Ivanshin, P. Jacobs, W. W. Jacobs, M. Janik, I. Johnson, P. G. Jones, E. G. Judd, M. Kaneta, M. Kaplan, D. Keane, J. Kiryluk, A. Kisiel, J. Klay, S. R. Klein, A. Klyachko, A. S. Konstantinov, M. Kopytine, L. Kotchenda, A. D. Kovalenko, M. Kramer, P. Kravtsov, K. Krueger, C. Kuhn, A. I. Kulikov, G. J. Kunde, C. L. Kunz, R. Kh. Kutuev, A. A. Kuznetsov, L. Lakehal-Ayat, M. A. C. Lamont, J. M. Landgraf, S. Lange, C. P. Lansdell, B. Lasiuk, F. Laue, A. Lebedev, R. Lednický, V. M. Leontiev, M. J. LeVine, Q. Li, S. J. Lindenbaum, M. A. Lisa, F. Liu, L. Liu, Z. Liu, Q. J. Liu, T. Ljubicic, W. J. Llope, G. LoCurto, H. Long, R. S. Longacre, M. Lopez-Noriega, W. A. Love, T. Ludlam, D. Lynn, J. Ma, R. Majka, S. Margetis, C. Markert, L. Martin, J. Marx, H. S. Matis, Yu. A. Matulenko, T. S. McShane, F. Meissner, Yu. Melnick, A. Meschanin, M. Messer, M. L. Miller, Z. Milosevich, N. G. Minaev, J. Mitchell, V. A. Moiseenko, C. F. Moore, V. Morozov, M. M. de Moura, M. G. Munhoz, J. M. Nelson, P. Nevski, V. A. Nikitin, L. V. Nogach, B. Norman, S. B. Nurushev, G. Odyniec, A. Ogawa, V. Okorokov, M. Oldenburg, D. Olson, G. Paic, S. U. Pandey, Y. Panebratsev, S. Y. Panitkin, A. I. Pavlinov, T. Pawlak, V. Perevoztchikov, W. Peryt, V. A Petrov, M. Planinic, J. Pluta, N. Porile, J. Porter, A. M. Poskanzer, E. Potrebenikova, D. Prindle, C. Pruneau, J. Putschke, G. Rai, G. Rakness, O. Ravel, R. L. Ray, S. V. Razin, D. Reichhold, J. G. Reid, F. Retiere, A. Ridiger, H. G. Ritter, J. B. Roberts, O. V. Rogachevski, J. L. Romero, A. Rose, C. Roy, V. Rykov, I. Sakrejda, S. Salur, J. Sandweiss, A. C. Saulys, I. Savin, J. Schambach, R. P. Scharenberg, N. Schmitz, L. S. Schroeder, A. Schüttauf, K. Schweda, J. Seger, D. Seliverstov, P. Seyboth, E. Shahaliev, K. E. Shestermanov, S. S. Shimanskii, V. S. Shvetcov, G. Skoro, N. Smirnov, R. Snellings, P. Sorensen, J. Sowinski, H. M. Spinka, B. Srivastava, E. J. Stephenson, R. Stock, A. Stolpovsky, M. Strikhanov, B. Stringfellow, C. Struck, A. A. P. Suaide, E. Sugarbaker, C. Suire, M. Šumbera, B. Surrow, T. J. M. Symons, A. Szanto de Toledo, P. Szarwas, A. Tai, J. Takahashi, A. H. Tang, J. H. Thomas, M. Thompson, V. Tikhomirov, M. Tokarev, M. B. Tonjes, T. A. Trainor, S. Trentalange, R. E. Tribble, V. Trofimov, O. Tsai, T. Ullrich, D. G. Underwood, G. Van Buren, A. M. VanderMolen, I. M. Vasilevski, A. N. Vasiliev, S. E. Vigdor, S. A. Voloshin, F. Wang, H. Ward, J. W. Watson, R. Wells, G. D. Westfall, C. Whitten, Jr., H. Wieman, R. Willson, S. W. Wissink, R. Witt, J. Wood, N. Xu, Z. Xu, A. E. Yakutin, E. Yamamoto, J. Yang, P. Yepes, V. I. Yurevich, Y. V. Zanevski, I. Zborovský, H. Zhang, W. M. Zhang, R. Zoulkarneev, and A. N. Zubarev (STAR Collaboration

Production of e+e−e^+e^- Pairs Accompanied by Nuclear Dissociation in Ultra-Peripheral Heavy Ion Collision

We present the first data on $e^+e^-$ pair production accompanied by nuclear breakup in ultra-peripheral gold-gold collisions at a center of mass energy of 200 GeV per nucleon pair. The nuclear breakup requirement selects events at small impact parameters, where higher-order corrections to the pair production cross section should be enhanced. We compare the pair kinematic distributions with two calculations: one based on the equivalent photon approximation, and the other using lowest-order quantum electrodynamics (QED); the latter includes the photon virtuality. The cross section, pair mass, rapidity and angular distributions are in good agreement with both calculations. The pair transverse momentum, $p_T$, spectrum agrees with the QED calculation, but not with the equivalent photon approach. We set limits on higher-order contributions to the cross section. The $e^+$ and $e^-$ $p_T$ spectra are similar, with no evidence for interference effects due to higher-order diagrams.Comment: 6 pages with 3 figures Slightly modified version that will appear in Phys. Rev.

Pion interferometry in Au+Au collisions at sNN\sqrt{\mathrm{s}_{_{\mathrm{NN}}}} = 200 GeV

We present a systematic analysis of two-pion interferometry in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV using the STAR detector at RHIC. We extract the HBT radii and study their multiplicity, transverse momentum, and azimuthal angle dependence. The Gaussianess of the correlation function is studied. Estimates of the geometrical and dynamical structure of the freeze-out source are extracted by fits with blast wave parameterizations. The expansion of the source and its relation with the initial energy density distribution is studied.Comment: 21 pages, 30 figures. As published in Physics Review

Multiplicity and Pseudorapidity Distributions of Charged Particles and Photons at Forward Pseudorapidity in Au + Au Collisions at sqrt{s_NN} = 62.4 GeV

We present the centrality dependent measurement of multiplicity and pseudorapidity distributions of charged particles and photons in Au + Au collisions at sqrt{s_NN} = 62.4 GeV. The charged particles and photons are measured in the pseudorapidity region 2.9 < eta < 3.9 and 2.3 < eta < 3.7, respectively. We have studied the scaling of particle production with the number of participating nucleons and the number of binary collisions. The photon and charged particle production in the measured pseudorapidity range has been shown to be consistent with energy independent limiting fragmentation behavior. The photons are observed to follow a centrality independent limiting fragmentation behavior while for the charged particles it is centrality dependent. We have carried out a comparative study of the pseudorapidity distributions of positively charged hadrons, negatively charged hadrons, photons, pions, net protons in nucleus--nucleus collisions and pseudorapidity distributions from p+p collisions. From these comparisons we conclude that baryons in the inclusive charged particle distribution are responsible for the observed centrality dependence of limiting fragmentation. The mesons are found to follow an energy independent behavior of limiting fragmentation while the behavior of baryons seems to be energy dependent.Comment: 17 pages and 20 figure

Particle-type dependence of azimuthal anisotropy and nuclear modification of particle production in Au+Au collisions at s(NN)**(1/2) = 200-GeV

We present STAR measurements of the azimuthal anisotropy parameter $v_2$ and the binary-collision scaled centrality ratio $R_{CP}$ for kaons and lambdas ($\Lambda+\bar{\Lambda}$) at mid-rapidity in Au+Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. In combination, the $v_2$ and $R_{CP}$ particle-type dependencies contradict expectations from partonic energy loss followed by standard fragmentation in vacuum. We establish $p_T \approx 5$ GeV/c as the value where the centrality dependent baryon enhancement ends. The $K_S^0$ and $\Lambda+\bar{\Lambda}$ $v_2$ values are consistent with expectations of constituent-quark-number scaling from models of hadron fromation by parton coalescence or recombination.Comment: 6 pages, 4 figures, 1 table. As published in PRL on Feb. 2, 2004; Significant revisions have been made to the text and color has been added to plot

Transverse momentum and collision energy dependence of high pTp_{T} hadron suppression in Au+Au collisions at ultrarelativistic energies

We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at \sqrtsNN=200 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5\lt\pT\lt12 GeV/c. The collision energy dependence of the yields and the centrality and \pT dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. We observe no evidence of \pT-dependent suppression, which may be expected from models incorporating jet attentuation in cold nuclear matter or scattering of fragmentation hadrons.Comment: Final journal version. Data tables for figures may be downloaded from the STAR home page: http://www.star.bnl.gov --> Publications --> Access to STAR published dat

Evidence from d+Au measurements for final-state suppression of high pTp_T hadrons in Au+Au collisions at RHIC

We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high $p_T$) in minimum bias and central d+Au collisions at $\sqrt{s_{NN}}$=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high $p_T$ previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.Comment: Final journal version. Data tables for figures may be downloaded from the STAR home page: http://www.star.bnl.gov --> Publications --> Access to STAR published dat