OPUS 4 | Search

Azimuthal anisotropy in Au+Au collisions at SNN=200GeV (2005)

J. Adams Jens Berger Thomas Dietel Thorsten Kollegger Jens Sören Lange Reinhard Stock et al. STAR Collaboration

The results from the STAR Collaboration on directed flow (v1), elliptic flow (v2), and the fourth harmonic (v4) in the anisotropic azimuthal distribution of particles from Au+Au collisions at sqrt[sNN]=200GeV are summarized and compared with results from other experiments and theoretical models. Results for identified particles are presented and fit with a blast-wave model. Different anisotropic flow analysis methods are compared and nonflow effects are extracted from the data. For v2, scaling with the number of constituent quarks and parton coalescence are discussed. For v4, scaling with v22 and quark coalescence are discussed.

Event-wise <pt> fluctuations in Au-Au collisions at sqrt[sNN]=130 GeV (2005)

J. Adams Clemens Adler Jens Berger Thomas Dietel Dominik Bernhard Flierl Thorsten Kollegger Jens Sören Lange L. J. Ruan Reinhard Stock Christof Struck et al. STAR Collaboration

We present the first large-acceptance measurement of event-wise mean transverse momentum <pt> fluctuations for Au-Au collisions at nucleon-nucleon center-of-momentum collision energy sqrt[sNN] = 130 GeV. The observed nonstatistical <pt> fluctuations substantially exceed in magnitude fluctuations expected from the finite number of particles produced in a typical collision. The r.m.s. fractional width excess of the event-wise <pt> distribution is 13.7±0.1(stat) ±1.3(syst)% relative to a statistical reference, for the 15% most-central collisions and for charged hadrons within pseudorapidity range | eta |<1,2 pi azimuth, and 0.15 <= pt <= 2 GeV/c. The width excess varies smoothly but nonmonotonically with collision centrality and does not display rapid changes with centrality which might indicate the presence of critical fluctuations. The reported <pt> fluctuation excess is qualitatively larger than those observed at lower energies and differs markedly from theoretical expectations. Contributions to <pt> fluctuations from semihard parton scattering in the initial state and dissipation in the bulk colored medium are discussed.

Open charm yields in d+Au collisions at sqrt[sNN]=200 GeV (2005)

J. Adams Jens Berger Thomas Dietel Thorsten Kollegger Jens Sören Lange Reinhard Stock et al. STAR Collaboration

Midrapidity open charm spectra from direct reconstruction of D0(D0-bar)-->K± pi ± in d+Au collisions and indirect electron-positron measurements via charm semileptonic decays in p+p and d+Au collisions at sqrt[sNN]=200 GeV are reported. The D0(D0-bar) spectrum covers a transverse momentum (pT) range of 0.1<pT<3 GeV/c, whereas the electron spectra cover a range of 1<pT<4 GeV/c. The electron spectra show approximate binary collision scaling between p+p and d+Au collisions. From these two independent analyses, the differential cross section per nucleon-nucleon binary interaction at midrapidity for open charm production from d+Au collisions at BNL RHIC is d sigma NNcc-bar/dy=0.30±0.04(stat)±0.09(syst) mb. The results are compared to theoretical calculations. Implications for charmonium results in A+A collisions are discussed.

Transverse-momentum dependent modification of dynamic texture in central Au+Au collisions at sqrt[sNN]=200GeV (2005)

J. Adams Jens Berger Thomas Dietel Thorsten Kollegger Jens Sören Lange Reinhard Stock et al. STAR Collaboration

Correlations in the hadron distributions produced in relativistic Au+Au collisions are studied in the discrete wavelet expansion method. The analysis is performed in the space of pseudorapidity (| eta | <= 1) and azimuth(full 2 pi ) in bins of transverse momentum (pt) from 0.14 <= pt <= 2.1GeV/c. In peripheral Au+Au collisions a correlation structure ascribed to minijet fragmentation is observed. It evolves with collision centrality and pt in a way not seen before, which suggests strong dissipation of minijet fragmentation in the longitudinally expanding medium.

Pion interferometry in Au+Au collisions at sqrt[sNN]=200GeV (2005)

J. Adams Jens Berger Thomas Dietel Thorsten Kollegger Jens Sören Lange Reinhard Stock et al. STAR Collaboration

We present a systematic analysis of two-pion interferometry in Au+Au collisions at sqrt[sNN]=200GeV using the STAR detector at Relativistic Heavy Ion Collider. We extract the Hanbury-Brown and Twiss radii and study their multiplicity, transverse momentum, and azimuthal angle dependence. The Gaussianness 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 parametrizations. The expansion of the source and its relation with the initial energy density distribution is studied.

K(892)* resonance production in Au+Au and p+p collisions at sqrt[sNN]=200GeV (2005)

J. Adams Jens Berger Thomas Dietel Thorsten Kollegger Jens Sören Lange Reinhard Stock et al. STAR Collaboration

The short-lived K(892)* resonance provides an efficient tool to probe properties of the hot and dense medium produced in relativistic heavy-ion collisions. We report measurements of K* in sqrt[sNN]=200GeV Au+Au and p+p collisions reconstructed via its hadronic decay channels K(892)*0-->K pi and K(892)*±-->K0S pi ± using the STAR detector at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The K*0 mass has been studied as a function of pT in minimum bias p+p and central Au+Au collisions. The K*pT spectra for minimum bias p+p interactions and for Au+Au collisions in different centralities are presented. The K*/K yield ratios for all centralities in Au+Au collisions are found to be significantly lower than the ratio in minimum bias p+p collisions, indicating the importance of hadronic interactions between chemical and kinetic freeze-outs. A significant nonzero K*0 elliptic flow (v2) is observed in Au+Au collisions and is compared to the K0S and Lambda v2. The nuclear modification factor of K* at intermediate pT is similar to that of K0S but different from Lambda . This establishes a baryon-meson effect over a mass effect in the particle production at intermediate pT (2<pT <= 4GeV/c).

L’institution de la littérature gabonaise : Partie I (2005)

Isaac Abaga Obiang Emmanuel Allogho Akue Annie-Michèlle Bouckandou et al.

Depuis bientôt trois (3) ans, le Docteur Heméry-Hervais SIMA-EYI enseignant et directeur en outre, du Centre d’études pour la littérature gabonaise(CELIG) anime à la faculté des lettres et des sciences humaines, notamment au sein du département des Littératures Africaines de l’Université Omar Bongo, un séminaire intitulé « Littérature et société au Gabon » . Ce séminaire vise à étudier, analyser la littérature gabonaise dans ses rapports apparents avec la société dans laquelle cette littérature est produite. Pour ce faire, le Docteur SIMA-EYI a demandé à ses étudiants de voir, dans l’optique d’un colloque sur la littérature gabonaise , quelle place les institutions littéraires(maisons d’éditions, universités, centres de recherche, ministères, etc.)accordent à la littérature produite dans notre pays . Ainsi, scindée en deux(2) groupes,l’un dirigé par Guy Wilfried IDIATHA et l’autre par Désiré Clitandre DZONTEU, la classe de licence des Littératures Africaines s’est donc penchée sur cet épineux problème. Notre équipe s’est intéressée au groupe bancaire BICIG et son concours littéraire et artistique ; au Théâtre national ; aux maisons d’éditions entre autres, La Maison Gabonaise du Livre, Ndzé, Hilaire Makaya et les éditions du silence ; l’Union des écrivains gabonais(UDEG), l’Ecole Normale supérieure(ENS) et l’organisation des Nations unies pour l’éducation , la science et la culture(UNESCO). Il est sans rappelé que ce travail ne fut pas une sinécure, plutôt parfois un parcours du combattant. -------------------------------------------------------------------------------------------- CRELAF (Cercle de Reflexion des Etudiants en Littératures Africaines), Département de Littératures Africaines, Université Omar Bongo, Gabon

L’institution de la littérature gabonaise : Partie II (2005)

Marc Rosaire Bissagou Kévin Bissielo Patricia Boundama et al.

Dans le cadre du Séminaire portant « sur la littérature et la société au Gabon », dirigé par monsieur SIMA EYI Hervais-Eméry, enseignant, Directeur-fondateur du Centre d’Etude en Littérature Gabonaise (CELIG), il a été demandé aux étudiants de faire des recherches et voir quelle place les institutions littéraires du Gabon accordait à la littérature gabonaise. Pour notre groupe, il s’est agit de se rendre dans les institutions telles que le Bureau Régional de l’Agence de la francophonie de l’Afrique Centrale (BRAC), Ministère de la culture, des arts et de l’éducation populaire, La Fondation Raponda WALKER, Le Centre Culturel Français ST- Exupéry de Libreville (CCF), La faculté des lettres et sciences humaines de l’Université Omar Bongo et L’Institut Pédagogique National (IPN). Notre objectif consistait à voir quel traitement ces institutions faisaient de la littérature gabonaise et comment elles s’y prenaient pour faciliter sa vulgarisation et sa promotion. Aussi , s’agissait-il d’étudier la nature des rapports ou des relations qui existent entre ces institutions et les écrivains gabonais, quelle place accordaient-elles à la littérature gabonaise et à ses écrivains, et comment procédaient -elles pour promouvoir cette littérature. -------------------------------------------------------------------------------------------- CRELAF (Cercle de Reflexion des Etudiants en Littératures Africaines), Département de Littératures Africaines, Université Omar Bongo, Gabon

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