Windows and Generalized Drinfeld Kernels

We develop a generalization of a construction of Drinfeld, first inspired by the Qconstruction of Ballard, Diemer, and Favero. We use this construction to provide kernels for Grassmann flops over an arbitrary field of characteristic zero. In the case of Grassmann flops this generalization recovers the kernel for a Fourier-Mukai functor on the derived category of the associated global quotient stack studied by Buchweitz, Leuschke, and Van den Bergh. We show an idempotent property for this kernel, which after restriction, induces a derived equivalence over any twisted form of a Grassmann flop

Kernels for Grassmann flops

We develop a generalization of the $Q$-construction of the first author, Diemer, and the third author for Grassmann flips. This generalization provides a canonical idempotent kernel on the derived category of the associated global quotient stack. The idempotent kernel, after restriction, induces a semi-orthogonal decomposition which compares the flipped varieties. Furthermore its image, after restriction to the geometric invariant theory semistable locus, "opens" a canonical "window" in the derived category of the quotient stack. We check this window coincides with the set of representations used by Kapranov to form a full exceptional collection on Grassmannians

Generalized Isoscaling of Isotopic Distributions

Generalized isoscaling relationships are proposed that may permit one to relate the isotopic distributions of systems that may not be at the same temperature. The proposed relationships are applied to multifragmentation excitation functions for central Kr+Nb and Ar+Sc collisions.Comment: 20 pages, 5 figure

Transverse momentum and collision energy dependence of high pTp_{T} hadron suppression in Au+Au collisions at ultrarelativistic energies

We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at \sqrtsNN=200 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5\lt\pT\lt12 GeV/c. The collision energy dependence of the yields and the centrality and \pT dependence of the suppression provide stringent constraints on theoretical models of suppression. Models incorporating initial-state gluon saturation or partonic energy loss in dense matter are largely consistent with observations. We observe no evidence of \pT-dependent suppression, which may be expected from models incorporating jet attentuation in cold nuclear matter or scattering of fragmentation hadrons.Comment: Final journal version. Data tables for figures may be downloaded from the STAR home page: http://www.star.bnl.gov --> Publications --> Access to STAR published dat

Disappearance of back-to-back high pTp_T hadron correlations in central Au+Au collisions at sNN\sqrt{s_{NN}} = 200 GeV

Azimuthal correlations for large transverse momentum charged hadrons have been measured over a wide pseudo-rapidity range and full azimuth in Au+Au and p+p collisions at $\sqrt{s_{NN}}$ = 200 GeV. The small-angle correlations observed in p+p collisions and at all centralities of Au+Au collisions are characteristic of hard-scattering processes already observed in elementary collisions. A strong back-to-back correlation exists for p+p and peripheral Au + Au. In contrast, the back-to-back correlations are reduced considerably in the most central Au+Au collisions, indicating substantial interaction as the hard-scattered partons or their fragmentation products traverse the medium.Comment: submitted to Phys. Rev. Let

Azimuthally sensitive Hanbury Brown-Twiss interferometry in Au+Au collisions at sqrt(s_{NN}) = 200 GeV

We present the results of a systematic study of the shape of the pion distribution in coordinate space at freeze-out in Au+Au collisions at RHIC using two-pion Hanbury Brown-Twiss (HBT) interferometry. Oscillations of the extracted HBT radii vs. emission angle indicate sources elongated perpendicular to the reaction plane. The results indicate that the pressure and expansion time of the collision system are not sufficient to completely quench its initial shape.Comment: 6 pages, 4 figures, published versio

Evidence from d+Au measurements for final-state suppression of high pTp_T hadrons in Au+Au collisions at RHIC

We report measurements of single-particle inclusive spectra and two-particle azimuthal distributions of charged hadrons at high transverse momentum (high $p_T$) in minimum bias and central d+Au collisions at $\sqrt{s_{NN}}$=200 GeV. The inclusive yield is enhanced in d+Au collisions relative to binary-scaled p+p collisions, while the two-particle azimuthal distributions are very similar to those observed in p+p collisions. These results demonstrate that the strong suppression of the inclusive yield and back-to-back correlations at high $p_T$ previously observed in central Au+Au collisions are due to final-state interactions with the dense medium generated in such collisions.Comment: Final journal version. Data tables for figures may be downloaded from the STAR home page: http://www.star.bnl.gov --> Publications --> Access to STAR published dat

Azimuthal anisotropy of K0s and Lambda prduction at mid-rapidity from Au+Au collisions at root s = 130 GeV

We report STAR results on the azimuthal anisotropy parameter v2 for strange particles K0S, L and Lbar at midrapidity in Au+Au collisions at sNN = 130 GeV at RHIC. The value of v2 as a function of transverse momentum of the produced particles pt and collision centrality is presented for both particles up to pt 3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2 measurement is compared with hydrodynamic model calculations. The physics implications of the pt integrated v2 magnitude as a function of particle mass are also discussed.Comment: 6 pages, 4 figures, by the STAR collaboratio

Pion-Xi correlations in Au-Au collisions at STAR

We present pion-Xi correlation analysis in Au-Au collisions at sqrt(s_NN)= 200 GeV and sqrt(s_NN) = 62.4 GeV, performed using the STAR detector at RHIC. A Xi*(1530) resonance signal is observed for the first time in Au-Au collisions. Experimental data are compared with theoretical predictions. The strength of the Xi* peak is reproduced in the correlation function assuming that pions and Xis emerge from a system in collective expansion.Comment: To appear in the proceedings of 18th Nuclear Physics Division Conference of the EPS (NPDC18),Prague, 23.8.-29.8. 200

Inclusive pi0 spectra at high transverse momentum in d-Au collisions at RHIC

Preliminary results on inclusive neutral pion production in d-Au collisions at sqrt(s_NN) = 200 GeV in the pseudo-rapidity range 0<eta<1 are presented. The measurement is performed using the STAR Barrel Electromagnetic calorimeter (BEMC). In this paper, the analysis of the first BEMC hadron measurement is described and the results are compared with earlier RHIC findings. The pi0 invariant differential cross sections show good agreement with next-to-leading order (NLO) perturbative QCD calculations.Comment: 4 pages, 5 figures, 18th Nuclear Physics Division Conference of the EPS, Prague, submitted to Nucl. Phys.