The results from the STAR Collaboration on directed flow (v 1 ), elliptic flow (v 2 ), and the fourth harmonic (v 4 ) in the anisotropic azimuthal distribution of particles from Au+Au collisions at √ s NN = 200 GeV 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 v 2 , scaling with the number of constituent quarks and parton coalescence are discussed. For v 4 , scaling with v 2 2 and quark coalescence are discussed.
Charged hadrons in [EQUATION: SEE TEXT] associated with particles of [EQUATION: SEE TEXT] are reconstructed in pp and Au+Au collisions at sqrt[sNN]=200 GeV. The associated multiplicity and p magnitude sum are found to increase from pp to central Au+Au collisions. The associated p distributions, while similar in shape on the nearside, are significantly softened on the awayside in central Au+Au relative to pp and not much harder than that of inclusive hadrons. The results, consistent with jet quenching, suggest that the awayside fragments approach equilibration with the medium traversed.
Ultra-relativistic Heavy-Ion Collision (HIC) generates very strong initial magnetic field ( B) inducing a vorticity in the reaction plane. The high B influences the evolution dynamics that is opposed by the large Faraday current due to electric field generated by the time varying B. We show that the resultant effects entail a significantly large directed flow (v1) of charm quarks (CQs) compared to light quarks due to a combination of several favorable conditions for CQs, mainly: (i) unlike light quarks formation time scale of CQs, τ f ≃ 0.1fm/c is comparable to the time scale when B attains its maximum value and (ii) the kinetic relaxation time of CQs is similar to the QGP lifetime, this helps the CQ to retain the initial kick picked up from the electromagnetic field in the transverse direction. The effect is also odd under charge exchange allowing to distinguish it from the vorticity of the bulk matter due to the initial angular momentum conservation; conjointly thanks to its mass, Mc >> ΛQCD, there should be no mixing with the chiral magnetic dynamics. Hence CQs provide very crucial and independent information on the strength of the magnetic field produced in HIC. 24.85.+p; 05.20.Dd; 12.38.Mh
PACS
In a coalescence plus fragmentation approach we calculate the heavy baryon/meson ratio and the pT spectra of charmed hadrons D 0 , Ds and Λ + c in a wide range of transverse momentum from low pT up to about 10 GeV and discuss their ratios from RHIC to LHC energies without any change of the coalescence parameters. We have included the contribution from decays of heavy hadron resonances and also the one due to fragmentation of heavy quarks which do not undergo the coalescence process. The coalescence process is tuned to have all charm quarks hadronizing in the pT → 0 limit and at finite pT charm quarks not undergoing coalescence are hadronized by independent fragmentation. The pT dependence of the baryon/meson ratios are found to be sensitive to the masses of coalescing quarks, in particular the Λc/D 0 can reach values of about 1 ÷ 1.5 at pT ≈ 3 GeV, or larger, similarly to the light baryon/meson ratio like p/π and Λ/K, however a marked difference is a quite weak pT dependence with respect to the light case, such that a larger value at intermediate pT implies a relatively large value also for the integrated yields. A comparison with other coalescence model and with the prediction of thermal model is discussed.
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