2,796 research outputs found

    Longitudinal Spin Asymmetry and Cross Section of Inclusive pi0 Production in Polarized p+p Collisions at RHIC

    Get PDF
    We present the first measurement of the cross section and the double longitudinal spin asymmetry of inclusive pi0 production in polarized p+p collisions at Sqrt(s) = 200 GeV at mid-rapidity with the STAR detector, using the barrel electromagnetic calorimeter. The measured cross section is compared to NLO pQCD calculations and can provide constraints on the pion fragmentation functions. Fragmentation is studied directly by measuring the momentum fraction of pi0 in jets, a quantity that is affected by the fragmentation process and jet reconstruction effects. The double longitudinal spin asymmetry is compared to NLO pQCD calculations based on different assumptions for the gluon polarization in the nucleon to provide constraints on delta g/g. At the present level of statistics the measured asymmetry disfavors a large positive gluon polarization, but can not yet distinguish between other scenarios.Comment: 4 pages, 2 figures, submitted to the proceedings of the 17th International Spin Physics Symposium (SPIN2006), Kyoto, Japan, October 2 to 7, 200

    An Integrated Tracker for STAR

    Get PDF
    The STAR experiment at the Relativistic Heavy Ion Collider RHIC studies the new state of matter produced in relativistic heavy ion collisions and the spin structure of the nucleon in collisions of polarized protons. In order to improve the capabilities for heavy flavor measurements and the reconstruction of charged vector bosons an upgrade of the tracking system both in the central and the forward region is pursued. The integrated system providing high resolution tracking and secondary vertex reconstruction capabilities will use silicon pixel, strip and GEM technology.Comment: 4 pages, 2 figures, to be published in the Proceedings of the 9th Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2006), Rio Grande, Puerto Rico, May 30 - June 3, 200

    Inclusive Hadron Production in p+p Collisions at STAR

    Get PDF
    The STAR experiment at RHIC has measured a variety of inclusive hadron cross sections in p+pp+p collisions at Sqrt(s) = 200 GeV. Measurements of the differential cross section for inclusive charged pion production at mid rapidity and for inclusive neutral pion production at forward rapidity (3.0 < eta < 4.2) as well as the first preliminary result from STAR for the differential cross section for inclusive neutral pion production near mid rapidity are presented. These cross sections are compared to next-to-leading order perturbative QCD calculations and can provide constraints on the pion fragmentation functions. Good agreement between data and pQCD has been found for all three cross sections.Comment: 4 pages, 1 figure, to be published in the Proceedings of the 9th Conference on the Intersections of Particle and Nuclear Physics (CIPANP 2006), Rio Grande, Puerto Rico, May 30 - June 3, 2006, v2 with updated reference

    Strangeness production in jets from p+p \sqrt{s} = 200 GeV collisions

    Full text link
    Measurements of strangeness production in jets help illuminate the QCD mechanisms in fragmentation. Furthermore, they provide a crucial baseline for heavy-ion studies where modifications in jet chemistry have recently been predicted. We present new results on strange particle production in jets from p+p \sqrt{s} = 200 GeV collisions measured by the STAR experiment. The momentum distributions of the \Lambda, \bar{\Lambda} and K0Short particles are obtained using various jet finding algorithms, and then compared to various models. Strange particle ratios in jets are obtained and compared to values obtained from the inclusive spectra. Finally, we show jets tagged with leading strange baryons and mesons, in order to investigate whether gluon or quark jets can be isolated in this way.Comment: 5 pages, 4 figures, Winter Workshop on Nuclear Dynamics 2010, Jamaic

    System Size Dependence of Particle Production at the SPS

    Full text link
    Recent results on the system size dependence of net-baryon and hyperon production as measured at the CERN SPS are discussed. The observed Npart dependences of yields, but also of dynamical properties, such as average transverse momenta, can be described in the context of the core corona approach. Other observables, such as antiproton yields and net-protons at forward rapidities, do not follow the predictions of this model. Possible implications for a search for a critical point in the QCD phase diagram are discussed. Event-by-event fluctuations of the relative core to corona source contributions might influence fluctuation observables (e.g. multiplicity fluctuations). The magnitude of this effect is investigated.Comment: 10 pages, 4 figurs. Proceedings of the 6th International Workshop on Critical Point and Onset of Deconfinement in Dubna, Aug. 201

    Firefly Flashing is Controlled by Gating Oxygen to Light-Emitting Cells

    Get PDF
    Although many aspects of firefly bioluminescence are understood, the mechanism by which adult fireflies produce light as discrete rapid flashes is not. Here we examine the most postulated theory, that flashing is controlled by gating oxygen access to the light-emitting cells (photocytes). According to this theory, the dark state represents repression of bioluminescence by limiting oxygen, which is required for bioluminescence; relief from this repression by transiently allowing oxygen access to the photocytes allows the flash. We show that normobaric hyperoxia releases the repression of light emission in the dark state of both spontaneously flashing and non-flashing fireflies, causing continual glowing, and we measure the kinetics of this process. Secondly, we determine the length of the barriers to oxygen diffusion to the photocytes in the aqueous and gas phases. Thirdly, we provide constraints upon the distance between any gas-phase gating structure(s) and the photocytes. We conclude from these data that the flash of the adult firefly is controlled by gating of oxygen to the photocytes, and demonstrate that this control mechanism is likely to act by modulating the levels of fluid in the tracheoles supplying photocytes, providing a variable barrier to oxygen diffusion

    Strange Particle Production at RHIC

    Get PDF
    We report STAR measurements of mid-rapidity yields for the Λ\Lambda, Λˉ\bar{\Lambda}, KS0K^{0}_{S}, Ξ\Xi^{-}, Ξˉ+\bar{\Xi}^{+}, Ω\Omega^{-}, and Ωˉ+\bar{\Omega}^{+} particles in Cu+Cu and Au+Au sNN=200\sqrt{s_{NN}} = 200 GeV collisions. We show that at a given number of participating nucleons, bulk strangeness production is higher in Cu+Cu collisions compared to Au+Au collisions at the same center of mass energy, counter to predictions from the Canonical formalism. We compare both the Cu+Cu and Au+Au yields to AMPT and EPOS predictions, and find they reproduce key qualitative aspects of the data. Finally, we investigate other scaling parameters and find bulk strangeness production for both the measured data and theoretical predictions, scales better with the number participants that undergo more than one collision.Comment: Conference proceedings for Hot Quarks 2008, 5 pages and 4 figure

    Genetic basis for variation in wheat grain yield in response to varying nitrogen application

    Get PDF
    Nitrogen (N) is a major nutrient needed to attain optimal grain yield (GY) in all environments. Nitrogen fertilisers represent a significant production cost, in both monetary and environmental terms. Developing genotypes capable of taking up N early during development while limiting biomass production after establishment and showing high N-use efficiency (NUE) would be economically beneficial. Genetic variation in NUE has been shown previously. Here we describe the genetic characterisation of NUE and identify genetic loci underlying N response under different N fertiliser regimes in a bread wheat population of doubled-haploid lines derived from a cross between two Australian genotypes (RAC875 × Kukri) bred for a similar production environment. NUE field trials were carried out at four sites in South Australia and two in Western Australia across three seasons. There was genotype-by-environment- by-treatment interaction across the sites and also good transgressive segregation for yield under different N supply in the population. We detected some significant Quantitative Trait Loci (QTL) associated with NUE and N response at different rates of N application across the sites and years. It was also possible to identify lines showing positive N response based on the rankings of their Best Linear Unbiased Predictions (BLUPs) within a trial. Dissecting the complexity of the N effect on yield through QTL analysis is a key step towards elucidating the molecular and physiological basis of NUE in wheat.Saba Mahjourimajd, Julian Taylor, Beata Sznajder, Andy Timmins, Fahimeh Shahinnia, Zed Rengel, Hossein Khabaz-Saberi, Haydn Kuchel, Mamoru Okamoto, Peter Langridg
    corecore