High-p_T azimuthal correlations of neutral strange baryons and mesons in STAR at RHIC

We present results on two-particle azimuthal correlations of high-$p_T$ neutral strange baryons ($\Lambda$,$\bar{\Lambda}$) and mesons ($K^0_S$) associated with non-identified charged particles in d+Au and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. In particular, we discuss properties of the near-side yield of associated charged particles as a function of centrality, transverse momentum and $z_T$, as well as possible baryon/meson and particle/antiparticle differences. The results are compared to the proton and pion triggered correlations and to fragmentation and recombination models.Comment: 3 pages, 2 figures, AIP proceedings of PANIC05 conference, Santa-Fe, New Mexico, USA, October 24-28, 200

Elliptic Flow and Semi-hard Scattering at SPS

Results on elliptic flow and two-particle correlations in the semi-hard regime are presented.Comment: 4 pages, 4 figures, 3 of which contain 2 eps file

Two and Three Particle Flavor Dependent Correlations

The PHENIX collaboration has developed novel methodologies for reliable extraction of jet functions from two and three particle azimuthal correlation functions measured at mid-rapidity in Au+Au collisions at $\sqrt s=200$ GeV. The extracted jet shape and the yield of jet-associated partner hadrons (per trigger hadron) are found to vary with particle type and collision centrality, indicating a significant effect of the nuclear collision medium on the (di)jet fragmentation process.Comment: Proceedings for Quark Matter 2005 parallel tal

Elliptic flow contribution to two-particle correlations at different orientations to the reaction plane

Collective anisotropic particle flow, a general phenomenon present in relativistic heavy-ion collisions, can be separated from direct particle-particle correlations of different physics origin by virtue of its specific azimuthal pattern. We provide expressions for flow-induced two-particle azimuthal correlations, if one of the particles is detected under fixed directions with respect to the reaction plane. We consider an ideal case when the reaction plane angle is exactly known, as well as present the general expressions in case of finite event-plane resolution. We foresee applications for the study of generic two-particle correlations at large transverse momentum originating from jet fragmentation.Comment: 5 pages, 3 figures, to be published as Rapid Communications in Phys.Rev.C Re-submit paper to with small improvements in text for better understanding, some minor changes in notation, and correcting one formula where a summation was forgotten. One new reference, one reference to conference report removed since full paper was already reference

High-pT strange particle spectra and correlations in STAR

We present results on strange particle production in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV. We discuss the nuclear modification factors ($R_{CP}$) and ratios of particle yields in order to investigate the range of anomalous baryon production.The medium modification of the fragmentation process is further explored by studying azimuthal correlations at intermediate-$p_T$ for $K^0_S$, $\Lambda$ and $\bar{\Lambda}$ trigger particles. The results are compared to fragmentation and recombination models.Comment: 4 pages, 3 figures. To appear in the proceedings of 2nd International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions (HP2006), Asilomar, California, USA, June 9-16, 200

Anisotropic flow background to jet-correlation relative to reaction plane: A revisit of the mathematical framework

We derive the flow-background formula for jet-correlation analysis with high pT trigger particles in any azimuth window relative to reaction plane, extending the mathematic framework of previous study in [J. Bielcikova, et al., Phys. Rev. C 69 (2004) 021901(R)].Comment: 4 pages, 1 figure, published versio

Using two- and Three-particle correlations to probe strongly interacting partonic matter

The latest two- and three-particle correlation measurements obtained by the PHENIX collaboration are presented. Three-particle correlations are consistent with the presence of conical emission patterns in the data. Two-particle correlations relative to the collision geometry reveal strong shape and yield modifications of the away-side jet, that depend on the orientation of the trigger particle with respect to the event plane. A difference in the geometry dependence of the per trigger yields in the regions around $\Delta\phi \approx \pi$ and $\Delta\phi \approx \pi \pm 1.1$ can be understood by a different geometry dependence of jet energy loss and the medium response to the deposited energy.Comment: 4 pages, 3 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Elliptic Flow arising from Ridges due to Semi-hard Scattering

Azimuthal anisotropy in heavy-ion collisions is studied by taking into account the ridges generated by semi-hard scattering of intermediate-momentum partons, which can be sensitive to the initial spatial configuration of the medium in non-central collisions. In a simple treatment of the problem where the recombination of only thermal partons is considered, analytical formulas can be derived that yield results in accord with the data on v_2 for p_T <1-2 GeV/c. Centrality dependence is described by a geometrical factor. Ridge phenomenology is used to determine the initial slopes of v_2 at low p_T for both pion and proton. For higher p_T, shower partons from high-p_T jets must be included, but they are not considered here.Comment: revised version with new title and expanded discussion, to be published in Phys. Lett.

Jet Correlations of Identified Particles in PHENIX

Azimuthal two particle correlations at intermediate $p_{T}$ with one of the particles identified have been measured at PHENIX. Trigger ($2.5 < p_{T} < 4.0 GeV/c$) baryons and mesons show little significant difference in the number of associated particles ($1.7 < p_{T} < 2.5 GeV/c$) independent of centrality. For inclusive hadron triggers with $2.5 < p_{T} < 4.0 GeV/c$, associated fragmentation particles with $1.0 < p_{T} < 2.5 GeV/c$ show a higher baryon to meson ratio on the away side.Comment: talk given at Quark Matter 2004, 4 pages 4 figur