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Correlations in the hadron distributions produced in relativistic Au+Au collisions are studied in the discrete wavelet expansion method. The analysis is performed in the space of pseudorapidity (| eta | <= 1) and azimuth(full 2 pi ) in bins of transverse momentum (pt) from 0.14 <= pt <= 2.1GeV/c. In peripheral Au+Au collisions a correlation structure ascribed to minijet fragmentation is observed. It evolves with collision centrality and pt in a way not seen before, which suggests strong dissipation of minijet fragmentation in the longitudinally expanding medium.
We report high statistics measurements of inclusive charged hadron production in Au+Au and p+p collisions at sqrt[sNN]=200 GeV. A large, approximately constant hadron suppression is observed in central Au+Au collisions for 5<pT<12 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 attenuation in cold nuclear matter or scattering of fragmentation hadrons.
The transversity distribution, which describes transversely polarized quarks in transversely polarized nucleons, is a fundamental component of the spin structure of the nucleon, and is only loosely constrained by global fits to existing semi-inclusive deep inelastic scattering (SIDIS) data. In transversely polarized p↑+p collisions it can be accessed using transverse polarization dependent fragmentation functions which give rise to azimuthal correlations between the polarization of the struck parton and the final state scalar mesons.This letter reports on spin dependent di-hadron correlations measured by the STAR experiment. The new dataset corresponds to 25 pb−1 integrated luminosity of p↑+p collisions at s=500 GeV, an increase of more than a factor of ten compared to our previous measurement at s=200 GeV. Non-zero asymmetries sensitive to transversity are observed at a Q2 of several hundred GeV and are found to be consistent with the former measurement and a model calculation. We expect that these data will enable an extraction of transversity with comparable precision to current SIDIS datasets but at much higher momentum transfers where subleading effects are suppressed.
Data from the first physics run at the Relativistic Heavy-Ion Collider at Brookhaven National Laboratory, Au+Au collisions at sqrt[sNN]=130 GeV, have been analyzed by the STAR Collaboration using three-pion correlations with charged pions to study whether pions are emitted independently at freeze-out. We have made a high-statistics measurement of the three-pion correlation function and calculated the normalized three-particle correlator to obtain a quantitative measurement of the degree of chaoticity of the pion source. It is found that the degree of chaoticity seems to increase with increasing particle multiplicity.
Larvae of thirty one species of antlions (Neuroptera: Myrmeleontidae) belonging to eleven genera live in the protection of cave mouths or large rock overhangs in Australia. New taxa proposed here include the following three new genera: Australeon, Newleon, Speleon. The following twelve new species are described: Froggattisca kakadu; Froggattisca rennerensis; Newleon fragilis; Speleon cavernicolus; Speleon pilliga; Speleon yallingup; Stenoleon xanthopsis; Xantholeon cavernicolus; Xantholeon kakadu; Xantholeon newi; Xantholeon pallens; Xantholeon pentlandensis. Two cave species are transferred into a new genus becoming new combinations: Australeon illustris (Gerstaecker), Australeon manselli (New and Matsura). The small non-cave species previously placed in Stenoleon Tillyard are transferred to Bandidus Navás, becoming B. gradostriatus (New), B. copleyensis (New), B. grandithecus (New), and B. navasi (New), new combinations. All known species of six genera (Stenoleon Tillyard, Xantholeon Tillyard, Eophanes Banks and three new genera) are known only in cave mouths. Also, species of Heoclisis Navás, Froggattisca Esben Petersen, Glenoleon Banks, Heoclisis Navás and Myrmeleon Linnaeus contain species living in cave mouths. Two main types of caves are found in Australia; those with loose organic material and those with loose inorganic material. The cave habitat is divided into four zones and several subzones. Many species are restricted to one zone or another but species of Stenoleon may overlap zones. Discussions of the species and some of their biological requirements are provided. One new parasite record is given, an undetermined species of Echthrobacella Girault (Hymenoptera: Encyrtidae) reared from the larvae of Speleon yallingup Miller and Stange. Diagnoses or descriptions are given for all of these cave species including distributional data. Keys to the cave mouth inhabiting antlions of Australia (adults and larvae) are provided including a revised key to the Xantholeon Tillyard.
We report results on rho (770)0--> pi + pi - production at midrapidity in p+p and peripheral Au+Au collisions at sqrt[sNN]=200 GeV. This is the first direct measurement of rho (770)0--> pi + pi - in heavy-ion collisions. The measured rho 0 peak in the invariant mass distribution is shifted by ~40 MeV/c2 in minimum bias p+p interactions and ~70 MeV/c2 in peripheral Au+Au collisions. The rho 0 mass shift is dependent on transverse momentum and multiplicity. The modification of the rho 0 meson mass, width, and shape due to phase space and dynamical effects are discussed.
A taxonomic study of the new world genus Dimarella has led to the recognition of 17 species, 9 of which are newly described. Three subgenera are recognized, one of which is described as new. Larvae are described for 11 species and biological data are given. Keys to adults and larvae are provided as well as photographs of larvae and taxonomic drawings. Distribution is summarized in maps.
We report on the rapidity and centrality dependence of proton and antiproton transverse mass distributions from 197Au + 197Au collisions at sqrt[sNN ]=130 GeV as measured by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). Our results are from the rapidity and transverse momentum range of |y| <0.5 and 0.35< pt <1.00 GeV/c . For both protons and antiprotons, transverse mass distributions become more convex from peripheral to central collisions demonstrating characteristics of collective expansion. The measured rapidity distributions and the mean transverse momenta versus rapidity are flat within |y| <0.5 . Comparisons of our data with results from model calculations indicate that in order to obtain a consistent picture of the proton (antiproton) yields and transverse mass distributions the possibility of prehadronic collective expansion may have to be taken into account.
The pseudorapidity asymmetry and centrality dependence of charged hadron spectra in d+Au collisions at sqrt[sNN ]=200 GeV are presented. The charged particle density at midrapidity, its pseudorapidity asymmetry, and centrality dependence are reasonably reproduced by a multiphase transport model, by HIJING, and by the latest calculations in a saturation model. Ratios of transverse momentum spectra between backward and forward pseudorapidity are above unity for pT below 5 GeV/c . The ratio of central to peripheral spectra in d+Au collisions shows enhancement at 2< pT <6 GeV/c , with a larger effect at backward rapidity than forward rapidity. Our measurements are in qualitative agreement with gluon saturation and in contrast to calculations based on incoherent multiple partonic scatterings.
We present data on e+ e- pair production accompanied by nuclear breakup in ultraperipheral gold-gold collisions at a center of mass energy of 200 GeV per nucleon pair. The nuclear breakup requirement selects events at small impact parameters, where higher-order diagrams for pair production should be enhanced. We compare the data with two calculations: one based on the equivalent photon approximation, and the other using lowest-order quantum electrodynamics (QED). The data distributions agree with both calculations, except that the pair transverse momentum spectrum disagrees with the equivalent photon approach. We set limits on higher-order contributions to the cross section.