Jet-like correlations between Forward- and Mid- rapidity in p+p, d+Au and Au+Au collisions from STAR at 200 GeV

In this proceedings we present STAR measurements of two particle azimuthal correlations between trigger particles at mid-rapidity ($|\eta|<$ 1) and associated particles at forward rapidities (2.7 $<|\eta|<$ 3.9) in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}}$= 200 GeV. Two particle azimuthal correlations between a mid-rapidity trigger particle and forward-rapidity associated particles preferably probe large-x quarks scattered off small-x gluons in RHIC collisions. Comparison of the separate d- and Au-side measurements in d+Au collisions may potentially probe gluon saturation and the presence of Color Glass Condensate. In Au+Au collisions quark energy loss can be probed at large rapidities, which may be different from gluon energy loss measured at mid-rapidity.Comment: Quark Matter 06 Conference proceedings, submitted to Journal of Phys.

Physics with Identified Particles at STAR

New physics results with identified particles at STAR are presented. Measurements at low $p_T$ address bulk properties of the collision, while those at high $p_T$ address jet energy loss in the bulk matter produced. Between these extremes, measurements at intermediate $p_T$ address the interplay between jets and the bulk. We highlight: measurements of $v_2$ fluctuations as a new, sensitive probe of the initial conditions and the equation of state; correlations involving multi-strange particles, along with ratios of identified particles to test coalescence as a mechanism of particle production at intermediate $p_T$; three particle azimuthal correlation to search for conical emission; and the energy and particle-type dependence of hadron production at high $p_T$ to study quark and gluon jet energy loss.Comment: 9 pages, 7 figures. To appear in the proceedings of the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter 2006), Shanghai, China, November 14-20, 200

π,K,p\pi, K, p and pˉ\bar{p} production from Au+Au collisions at sNN=62.4\sqrt{s_{_{NN}}} = 62.4 GeV

The preliminary results of $\pi^{\pm}, K^{\pm}, p$ and $\bar{p}$ spectra are reported from Au+Au collisions at $\sqrt{s_{_{NN}}} = 62.4$ GeV. Particle identification is from the Time Projection Chamber and Time-of-Flight system at STAR. The nuclear modification factor $R_{CP}$ for mesons ($\pi^{\pm}, K^{\pm}$) and baryons ($p, \bar{p}$) will also be discussed.Comment: 5 pages, 4 figures, Contributed to 8th International Conference on Strangeness in Quark Matter (SQM 2004),to be published in Journal of Physics

Anomalous centrality variation of minijet angular correlations in Au-Au collisions at 62 and 200 GeV from STAR

We have measured 2D autocorrelations for all charged hadrons in STAR with $p_{t}$ $>$ 0.15 GeV/c and $| \eta |$ $<$ 1 from Au+Au collisions at 62 and 200 GeV. The correlation structure is dominated by a peak centered at zero relative opening angles on $\eta$ and $\phi$ which we hypothesize is caused by minimum-bias jets (minijets). We observe a large excess of minijet correlations in more-central Au-Au collisions relative to binary-collision scaling (more correlated pairs than expected from surface emission or even volume emission). We also observe a sudden increase of the minijet peak amplitude and $\eta$ width relative to binary-collision scaling of scattered partons which occurs at an energy-dependent centrality point. There is a possible scaling of the transition point with transverse particle density.Comment: Quark Matter 2008 proceedings, submitted to Journal of Physics G. v2: added STAR Collaboration to author lis

K* production in Cu+Cu and Au+Au collisions at sqrt(s_{NN}) = 62.4 GeV and 200 GeV in STAR

We report the measurements of $p_T$ spectra of $K^*$ up to intermediate $p_T$ region in mid-rapidity through its hadronic decay channel using the STAR detector in Au+Au and Cu+Cu collisions at $\sqrt{s_{\mathrm{NN}}}$= 62.4 GeV and 200 GeV. Particle ratios such as $K^{*}/K$ and $K^{*}/\phi$ is used to understand the rescattering and regeneration effect on $K^{*}$ production in the hadronic medium. The $K^*$ $v_{2}$ measurement using a high statistics Au+Au 200 GeV dataset and nuclear modification factor measurement supports the quark coalescence model of particle production in the intermediate $p_T$ range.Comment: 5 page

Centrality dependence of the N(Ω)/N(ϕ)N(\Omega)/N(\phi) ratios and ϕ\phi v2v_{2} - a test of thermalization in Au+Au collisions at RHIC

We present the centrality dependence of the $N(\Omega)/N(\phi)$ ratios and $\phi$ $v_{2}$ measured in Au+Au collisions at $\sqrt{s_{NN}}=200$ GeV by the STAR experiment at RHIC. The results are compared to measurements of other identified particles and recombination model expectations in order to gain insight into the partonic collectivity and possible thermalization of the produced medium.Comment: 4 pages, 2 figures, Quark Matter 2006 conference proceeding

Upsilon cross section in p+p collisions at STAR

The main focus of the heavy flavor program at RHIC is to investigate the properties of the dense matter produced in heavy-ion collisions by studying its effect on open heavy flavor and quarkonia production. This in turn requires a detailed understanding of their production in elementary p+p collisions so that the dense matter effects can be later unfolded. In this paper, we present the first mid-rapidity cross section measurement of bottomonium at $\sqrt{s}=200$ GeV with the STAR experiment. We compare our results with perturbative QCD calculations. A brief status on the study of charmonium in STAR is given.Comment: 4 pages, 4 figures. To appear in the proceedings of Quark Matter 2006 as a special issue of Journal of Physics G: Nuclear and Particle Physic

The first measurement of BB meson semi-leptonic decay contribution to non-photonic electrons at RHIC

We present the first measurement for the $B$ meson semi-leptonic decay contribution to non-photonic electrons at RHIC using non-photonic electron azimuthal correlations with charged hadrons in p+p collisions at $\sqrt{s_{NN}} = 200$ GeV from STAR.Comment: 4 pages, 3 figures, Quark Matter 2006 Proceedings, to appear in J. Phys.

STAR's measurement of Long-range forward-backward multiplicity correlations as the signature of "dense partonic matter" in the Heavy Ion collisions at sNN=\sqrt{s_{NN}}=200 GeV.}

Forward-backward multiplicity correlations have been measured with the STAR detector for Au+Au, Cu+Cu and {\it p+p} collisions at $\sqrt{s_{NN}}$ = 200 GeV. A strong, long-range correlation is observed for central heavy ion collisions that vanishes in semi-peripheral events and {\it pp} collisions. There is no apparent scaling of correlation strength with the number of participants involved in the collision. Both the Dual Parton Model and the Color Glass condensate indicate that the long range correlations are due to multiple parton interactions. This suggests that the dense partonic matter might have been created in mid-central and central Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV.Comment: 4 pages, 3 figures,presented at the 19th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, "Quark Matter 2008", Jaipur, India, February 4-10, 200

Υ\Upsilon production in p+p and Au+Au collisions in STAR

The study of quarkonium production in relativistic heavy ion collisions provides insight into the properties of the produced medium. The lattice studies show a sequential suppression of quarkonia states when compared to normal nuclear matter; which further affirms that a full spectroscopy including bottomonium can provide us a better thermometer for the matter produced under extreme conditions in relativistic heavy ion collisions. With the completion of the STAR Electromagnetic Calorimeter and with the increased luminosity provided by RHIC in Run 6 and 7, the study of $\Upsilon$ production via the di-electron channel becomes possible. We present the results on $\Upsilon$ measurements in p+p collisions (from Run 6) along with the first results from Au+Au collisions (in Run 7) at $\sqrt{s_{\rm{NN}}} = 200$ GeV from the STAR experiment.Comment: 4 pages and 2 figures, Oral Presentation at QM2008 February 4-10, 2008: Jaipur India. submitted to Journal Of Physics-G:Nuclear and Particle Physic