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Production de particules doublement étranges dans les collisions d'ions lourds ultra-relativistes à √(SNN) = 130 GeV

Abstract : The study of strangeness production in ultra-relativistic heavy ions collisions is one possible tool used to probe the formation of the new deconfined state of nuclear matter : the Quark Gluon Plasma (QGP). Within this framework, we present the first study of multi-strange baryons Ξ- and anti-Ξ+, production, in Au+Au collisions at √(SNN) = 130 GeV measured by the STAR experiment at RHIC. After an introduction, both theoretical and experimental, of the context and interest of such a measurement, we describe how multi-strange baryons are reconstructed in the STAR Time Projection Chamber (TPC) using the topology of their decay. We discuss the optimization of the selection criteria used for increasing the quality of the observed signal, and we explain the calculation of the detector acceptance and efficiency corrections used for obtaining the corrected Ξ- and anti-Ξ+, transverse momentum spectra. The measured anti-Ξ+/Ξ- ratio is almost a factor 4 larger than the one measured at √(SNN) = 17.3 GeV at CERN-SPS, indicating a strong decrease of the net-baryon density at mid-rapidity. The invariant yields of Ξ- and anti-Ξ+ at mid-rapidity increase linearly with the centrality of the collision. For the most central collisions we found those yields to be 2.30 ± 0.09 Ξ-/evt. and 1.89 ± 0.08 anti-Ξ+/evt. Independently of the collision centrality, we obtained the same inverse slope parameter for Ξ- and anti-Ξ+. Finally, this inverse slope parameter seems to deviate from a picture of transverse flow together with lighter particles produced in the collision.
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Javier Castillo. Production de particules doublement étranges dans les collisions d'ions lourds ultra-relativistes à √(SNN) = 130 GeV. Physique Nucléaire Expérimentale [nucl-ex]. Université Paris 7 - Denis Diderot, 2002. Français. ⟨tel-02907610⟩

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