3,644 research outputs found

    Event by event di-hadron correlations in Pb-Pb 2.76 TeV collisions from the ALICE experiment

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    The large multiplicities at the LHC may permit flow harmonics to be determined on an event by event basis in Pb-Pb collisions. We extract these harmonics from event by event di-hadron correlations. Within a fine centrality bin, we find the correlation function varies substantially on an event by event basis, indicating large fluctuations in the initial conditions for a given impact parameter. Such large fluctuations lead to some events being highly triangular or highly elliptical, where the angular correlation function is completely dominated by the respective second and third Fourier harmonics. We will show unfolded v2v_{2} distributions for various centralities, and implications for our understanding of the initial conditions.Comment: 4 pages, Hot Quarks 201

    Untriggered di-hadron correlations in Pb-Pb collisions at sNN=\sqrt{s_{NN}} = 2.76 TeV from ALICE

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    We present measurements of untriggered di-hadron correlations as a function of centrality in Pb-Pb \sNN collisions, for charged hadrons with pT>0.15p_{T} > 0.15 GeV/c/c. These measurements provide a map of the bulk correlation structures in heavy-ion collisions. Contributions to these structures may come from jets, initial density fluctuations, elliptic flow, resonances, and/or momentum conservation. We decompose the measured correlation functions via a multi-parameter fit in order to extract the nearside Gaussian, the longer range Δη\Delta \eta correlation often referred to as the soft ridge. The effect of including higher harmonics (v3v_{3} and v4v_{4}) in this procedure will be discussed. We investigate how the nearside Gaussian scales with the number of binary collisions. Finally, we show the charge dependence of the nearside Gaussian.Comment: 4 pages, QM 2011 proceeding

    A study of first month space malfunctions

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    The study examines the first-month space performance of 57 Goddard Space Flight Center spacecraft. It is a sequel to a previous study of first-day space malfunctions of the same 57 spacecraft. A total of 154 malfunctions, of which 88 were classified as failures, have been summarized by year of occurrence, by major subsystem of a spacecraft, by type of defect, and by severity. Of the 57 spacecraft, 45 had one or more failures during the first month in space. However, the mission criticality data show that, of the 154 malfunctions, less than 10 percent would have resulted in major loss (50-100 percent) to the mission, and due to redundancy, only 5 percent did result in major loss to the mission. The data show that more than 50 percent of the first month's failures occurred in the first operational day in space. The data also show that, for the first month in space, the ratio of system-test failures to space failures for various devices ranged from 3 to 1 up to 10 to 1. For six spacecraft programs, the ratios of test to space failures ranged from 2 to 1 up to 8 to 1

    A study of total space life performance of GSFC spacecraft

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    The space life performance of 57 Goddard Space Flight Center spacecraft is given. The time distribution of 449 malfunctions, of which 248 were classified as failures, is presented. Test data were available for 39 of the spacecraft and permitted a comparison of system test performance with the first-day, first-month, and total space life performance. The failures per spacecraft for the system environmental tests and the three time periods in space were 12, 0.9, 1.7, and 5.0, respectively. Relevance of the data to the pre-shuttle and shuttle eras is discussed. Classifications of failures by type of device and spacecraft subsystem are included. A continuation of the Goddard philosophy of requiring a system-level environmental test program is justified

    The Centrality Dependence of Strange Baryon and Meson Production in Cu+Cu and Au+Au sqrt(s_NN) = 200 GeV collisions

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    Transverse momentum spectra of Lambda and K0Short particles are presented for Cu+Cu sqrt(s_NN) = 200 GeV collisions observed at STAR, and compared to Au+Au measurements at the same energy. For both systems, a number of observables are shown to increase at mid-rapidity (|y| < 0.5) with increasing centrality. These are the integrated Lambda and K0Short yields, the integrated Lambda and K0Short yields per participating nucleon, and mid-pT (1 GeV/c -> 4.5 GeV/c) Lambda/KK0Short ratios. The RCP ratio is found to be higher for the Lambda yields at mid-pT compared to the K0Short yields for both the Cu+Cu and Au+Au data. In contrast, when similar numbers of participating nucleons are considered for the Cu+Cu and Au+Au data, an indication of increased bulk strangeness production and a higher mid-pT (1 -> 4.5 GeV/c) Lambda/K0Short ratio are found, for Cu+Cu.Comment: Quark Matter 2006 Proceeding

    Experience in Thermal-vacuum Testing Earth Satellites at Goddard Space Flight Center

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    Thermal-vacuum environmental testing of satellite

    Failure rate analysis of Goddard Space Flight Center spacecraft performance during orbital life

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    Space life performance data on 57 Goddard Space Flight Center spacecraft are analyzed from the standpoint of determining an appropriate reliability model and the associated reliability parameters. Data from published NASA reports, which cover the space performance of GSFC spacecraft launched in the 1960-1970 decade, form the basis of the analyses. The results of the analyses show that the time distribution of 449 malfunctions, of which 248 were classified as failures (not necessarily catastrophic), follow a reliability growth pattern that can be described with either the Duane model or a Weibull distribution. The advantages of both mathematical models are used in order to: identify space failure rates, observe chronological trends, and compare failure rates with those experienced during the prelaunch environmental tests of the flight model spacecraft

    Strangeness Production in Heavy-Ion Collisions at STAR

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    We report an overview of strangeness production in Cu+Cu and Au+Au collisions at the energies sNN=\sqrt{s_{NN}} = 62.4 and 200 GeV. We show new mid-rapidly dN/dydN/dy results for the KS0K^{0}_{S}, Λ\Lambda, Ξ\Xi, Ω\Omega particles in Cu+Cu \sNN{62} collisions and compare to results in Au+Au \sNN{62} collisions. We show new results for mid-pTp_T Λ/KS0\Lambda/K^{0}_{S} ratios in Cu+Cu \sNN{62} collisions and again compare to ratios in Au+Au \sNN{62} collisions. Finally, we show the high-pTp_{T} (∼6.2\sim 6.2 GeV/c) RAA(KS0)R_{AA}(K^{0}_{S}) as a function of system size in Au+Au \sNN{200} collisions and compare to RAA(π)R_{AA}(\pi).Comment: 4 pages, 3 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse
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