Strange hadron (neutral kaon(short), lambda baryon and Xi baryon) production in deuteron+gold collisions at center of mass energy = 200 GeV at RHIC.

摘要

The study of identified particles from deuteron(d)+gold(Au) collisions provide a crucial reference to investigate nuclear effects observed in Au+Au collisions where a thermalized partonic state - Quark Gluon Plasma (QGP) - is thought to have been created.; The measurements of transverse mass (mT) and momentum (pT) spectra at mid-rapidity (| y| 1) for the identified strange hadrons: K0S , Λ + Λ and xi- + xi+ from d+Au collisions are presented. The measured pT covers 0.4 p T 6.0 GeV/c for K0S and Λ + Λ and 0.6 pT 5.0 GeV/c for xi- + xi+. These particles were reconstructed from the topological characteristics of their weak decays in the STAR Time Projection Chamber (TPC).; The mT spectra of these particles are well described by a double exponential function which can be understood by two component models: soft (thermal) hadron production at low mT and hard hadron production at high mT. The integrated yields (dN/dy) and mean pT ( pT >) of these particles are calculated from the fit functions for different centralities. The dN/dy normalized to the number of participants (Npart) increase with Npart. The Λ(Λ ) dN/dy values at the mid-rapidity and forward rapidity regions agree with the EPOS model calculations.; The measured Λ/ K0S ratios show the greatest baryon enhancement at pT ∼ 2 GeV/c in d+Au collisions. The strangeness enhancement going from d+Au to Au+Au collisions grows with the number of strange quark in a hadron. The magnitude of the enhancement is in the same order as the SPS measurement.; The nuclear modification factors RCP normalized to binary collisions indicate that the Cronin effect in d+Au collisions has a distinct particle type dependence. The RCP ratios show a distinct baryon versus meson dependence: the RCP for xi- + xi+ follows that for Λ + Λ while the R CP for the &phis; is close to that for the K0S . The mechanism based on initial hadron or parton multiple scattering is not sufficient to explain this particle type dependence. Hadronization processes through multi-parton dynamics such as coalescence and recombination models are likely to be important for explaining baryon enhancement and the Cronin effect in high-energy d+Au collisions.