First Result of Net-Charge Jet-Correlations from STAR

We presented results on azimuthal correlation of net-charge with high $p_T$ trigger particles. It is found that the net-charge correlation shape is similar to that of total-charge. On the near-side, the net-charge and total-charge $p_T$ spectra have similar shape and both are harder than the inclusives. On the away-side, the correlated spectra are not much harder than the inclusives, and the net-charge/total-charge ratio increases with $p_T$ and is similar to the inclusive ratio

Jet Correlations with Identified Particles from PHENIX: Methods and Results

Azimuthal angle two particle correlations have been shown to be a powerful probe for extracting novel features of the interaction between hard scattered partons and the medium produced in Au+Au collisions at RHIC. At intermediate $p_T$, 2-5GeV/c, the jets have been shown to be significantly modified in both their particle composition and their angular distribution compared to p+p collisions. Additionally, angular two particle correlations with identified hadrons provide information on the possible role of modified hadronization scenarios such as partonic recombination, which might allow medium modified jet fragmentation by connecting hard scattered partons to low $p_T$ thermal partons. PHENIX has excellent particle identification capabilities and has developed robust techniques for extracting jet correlations from the large underlying event. We present recent PHENIX results from Au+Au collisions for a variety of $p_T$ and particle type combinations. We also present p+p measurements as a baseline. We show evidence that protons and anti-protons in the $p_T$ region of enhanced baryon and anti-baryon single particle production are produced in close angle pairs of opposite charge and that the strong modifications to the away side shape observed for charged hadron correlations are also present when baryons are correlated.Comment: talk given at XIth International Workshop on Correlations and Fluctuations in Multiparticle Production, Hangzhou China November 21-24 200

Test of Chemical freeze-out at RHIC

We present the results of a systematic test applying statistical thermal model fits in a consistent way for different particle ratios, and different system sizes using the various particle yields measured in the STAR experiment. Comparison between central and peripheral Au+Au and Cu+Cu collisions with data from p+p collisions provides an interesting tool to verify the dependence with the system size. We also present a study of the rapidity dependence of the thermal fit parameters using available data from RHIC in the forward rapidity regions and also using different parameterization for the rapidity distribution of different particles.Comment: SQM2008 conference proceeding

Forward Λ production and nuclear stopping power in d+Au collisions at √sNN=200 GeV

We report the measurement of Λ and Λ¯ yields and inverse slope parameters in d+Au collisions at √sNN=200 GeV at forward and backward rapidities (y=±2.75), using data from the STAR forward time projection chambers. The contributions of different processes to baryon transport and particle production are probed exploiting the inherent asymmetry of the d+Au system. Comparisons to model calculations show that baryon transport on the deuteron side is consistent with multiple collisions of the deuteron nucleons with gold participants. On the gold side, HIJING-based models without a hadronic rescattering phase do not describe the measured particle yields, while models that include target remnants or hadronic rescattering do. The multichain model can provide a good description of the net baryon density in d+Au collisions at energies currently available at the BNL Relativistic Heavy Ion Collider, and the derived parameters of the model agree with those from nuclear collisions at lower energies

Transverse Momentum and Centrality Dependence of High-pT Nonphotonic Electron Suppression in Au+Au Collisions at √sNN=200 GeV.

The STAR collaboration at the BNL Relativistic Heavy-Ion Collider (RHIC) reports measurements of the inclusive yield of nonphotonic electrons, which arise dominantly from semileptonic decays of heavy flavor mesons, over a broad range of transverse momenta (1.2<pT<10  GeV/c) in p+p, d+Au, and Au+Au collisions at √sNN=200  GeV. The nonphotonic electron yield exhibits an unexpectedly large suppression in central Au+Au collisions at high pT, suggesting substantial heavy-quark energy loss at RHIC. The centrality and pT dependences of the suppression provide constraints on theoretical models of suppression

Long range rapidity correlations and jet production in high energy nuclear collisions

The STAR Collaboration at the Relativistic Heavy Ion Collider presents a systematic study of high-transverse-momentum charged-di-hadron correlations at small azimuthal pair separation Δϕ in d+Au and central Au+Au collisions at √sNN=200 GeV. Significant correlated yield for pairs with large longitudinal separation Δη is observed in central Au+Au collisions, in contrast to d+Au collisions. The associated yield distribution in Δη×Δϕ can be decomposed into a narrow jet-like peak at small angular separation which has a similar shape to that found in d+Au collisions, and a component that is narrow in Δϕ and depends only weakly on Δη, the “ridge.” Using two systematically independent determinations of the background normalization and shape, finite ridge yield is found to persist for trigger pt>6 GeV/c, indicating that it is correlated with jet production. The transverse-momentum spectrum of hadrons comprising the ridge is found to be similar to that of bulk particle production in the measured range (2<pt<4 GeV/c)

Stem cell highways: signalling beats trafficking?

status: publishe