3,644 research outputs found
Event by event di-hadron correlations in Pb-Pb 2.76 TeV collisions from the ALICE experiment
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 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 2.76 TeV from ALICE
We present measurements of untriggered di-hadron correlations as a function
of centrality in Pb-Pb \sNN collisions, for charged hadrons with
GeV. 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
correlation often referred to as the soft ridge. The effect of
including higher harmonics ( and ) 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
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
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
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
Thermal-vacuum environmental testing of satellite
Failure rate analysis of Goddard Space Flight Center spacecraft performance during orbital life
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
We report an overview of strangeness production in Cu+Cu and Au+Au collisions
at the energies 62.4 and 200 GeV. We show new mid-rapidly
results for the , , , particles in
Cu+Cu \sNN{62} collisions and compare to results in Au+Au \sNN{62} collisions.
We show new results for mid- ratios in Cu+Cu \sNN{62}
collisions and again compare to ratios in Au+Au \sNN{62} collisions. Finally,
we show the high- ( GeV/c) as a function
of system size in Au+Au \sNN{200} collisions and compare to .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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