828 research outputs found
Alignement experience in STAR
The STAR experiment at RHIC uses four layers of silicon strip and silicon drift detectors for secondary vertex reconstruction. An attempt for a direct charm meson measurement put stringent requirements on alignment and calibration. We report on recent alignment and drift velocity calibration work performed on the inner silicon tracking system
Azimuthal anisotropy and correlations in the hard scattering regime at RHIC
Azimuthal anisotropy () and two-particle angular correlations of high
charged hadrons have been measured in Au+Au collisions at
=130 GeV for transverse momenta up to 6 GeV/c, where hard
processes are expected to contribute significantly. The two-particle angular
correlations exhibit elliptic flow and a structure suggestive of fragmentation
of high partons. The monotonic rise of for GeV/c is
consistent with collective hydrodynamical flow calculations. At \pT>3 GeV/c a
saturation of is observed which persists up to GeV/c.Comment: As publishe
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
Disappearance of back-to-back high hadron correlations in central Au+Au collisions at = 200 GeV
Azimuthal correlations for large transverse momentum charged hadrons have
been measured over a wide pseudo-rapidity range and full azimuth in Au+Au and
p+p collisions at = 200 GeV. The small-angle correlations
observed in p+p collisions and at all centralities of Au+Au collisions are
characteristic of hard-scattering processes already observed in elementary
collisions. A strong back-to-back correlation exists for p+p and peripheral Au
+ Au. In contrast, the back-to-back correlations are reduced considerably in
the most central Au+Au collisions, indicating substantial interaction as the
hard-scattered partons or their fragmentation products traverse the medium.Comment: submitted to Phys. Rev. Let
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
Correlations in STAR: interferometry and event structure
STAR observes a complex picture of RHIC collisions where correlation effects
of different origins -- initial state geometry, semi-hard scattering,
hadronization, as well as final state interactions such as quantum intensity
interference -- coexist. Presenting the measurements of flow, mini-jet
deformation, modified hadronization, and the Hanbury Brown and Twiss effect, we
trace the history of the system from the initial to the final state. The
resulting picture is discussed in the context of identifying the relevant
degrees of freedom and the likely equilibration mechanism.Comment: 8 pages, 6 figures, plenary talk at the 5th International Conference
on Physics and Astrophysics of Quark Gluon Plasma, to appear in Journal of
Physics G (http://www.iop.org
Azimuthal anisotropy and correlations at large transverse momenta in p+p and Au+Au collisions at sqrt[sNN] = 200 GeV
Results on high transverse momentum charged particle emission with respect to the reaction plane are presented for Au+Au collisions at sqrt[sNN]=200 GeV. Two- and four-particle correlations results are presented as well as a comparison of azimuthal correlations in Au+Au collisions to those in p+p at the same energy. The elliptic anisotropy v2 is found to reach its maximum at pt~3 GeV/c, then decrease slowly and remain significant up to pt ~ 7-10 GeV/c. Stronger suppression is found in the back-to-back high-pt particle correlations for particles emitted out of plane compared to those emitted in plane. The centrality dependence of v2 at intermediate pt is compared to simple models based on jet quenching
Elliptic flow from two- and four-particle correlations in Au + Au collisions at sqrt{s_{NN}} = 130 GeV
Elliptic flow holds much promise for studying the early-time thermalization
attained in ultrarelativistic nuclear collisions. Flow measurements also
provide a means of distinguishing between hydrodynamic models and calculations
which approach the low density (dilute gas) limit. Among the effects that can
complicate the interpretation of elliptic flow measurements are azimuthal
correlations that are unrelated to the reaction plane (non-flow correlations).
Using data for Au + Au collisions at sqrt{s_{NN}} = 130 GeV from the STAR TPC,
it is found that four-particle correlation analyses can reliably separate flow
and non-flow correlation signals. The latter account for on average about 15%
of the observed second-harmonic azimuthal correlation, with the largest
relative contribution for the most peripheral and the most central collisions.
The results are also corrected for the effect of flow variations within
centrality bins. This effect is negligible for all but the most central bin,
where the correction to the elliptic flow is about a factor of two. A simple
new method for two-particle flow analysis based on scalar products is
described. An analysis based on the distribution of the magnitude of the flow
vector is also described.Comment: minor text change
Multiplicity distribution and spectra of negatively charged hadrons in Au+Au collisions at sqrt(s_nn) = 130 GeV
The minimum bias multiplicity distribution and the transverse momentum and
pseudorapidity distributions for central collisions have been measured for
negative hadrons (h-) in Au+Au interactions at sqrt(s_nn) = 130 GeV. The
multiplicity density at midrapidity for the 5% most central interactions is
dNh-/deta|_{eta = 0} = 280 +- 1(stat)+- 20(syst), an increase per participant
of 38% relative to ppbar collisions at the same energy. The mean transverse
momentum is 0.508 +- 0.012 GeV/c and is larger than in central Pb+Pb collisions
at lower energies. The scaling of the h- yield per participant is a strong
function of pt. The pseudorapidity distribution is almost constant within
|eta|<1.Comment: 6 pages, 3 figure
Probing BFKL Dynamics in the Dijet Cross Section at Large Rapidity Intervals in ppbar Collisions at sqrt{s}=1800 and 630 GeV
Inclusive dijet production at large pseudorapidity intervals (delta_eta)
between the two jets has been suggested as a regime for observing BFKL
dynamics. We have measured the dijet cross section for large delta_eta in ppbar
collisions at sqrt{s}=1800 and 630 GeV using the DO detector. The partonic
cross section increases strongly with the size of delta_eta. The observed
growth is even stronger than expected on the basis of BFKL resummation in the
leading logarithmic approximation. The growth of the partonic cross section can
be accommodated with an effective BFKL intercept of
a_{BFKL}(20GeV)=1.65+/-0.07.Comment: Published in Physical Review Letter
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