3,176 research outputs found
Review of the Brayton engine electrical subsystem design and computerized technique used to document wiring
Brayton engine electrical subsystem design and computerized technique used to document wirin
Medium-Induced Gluon Radiation off Massive Quarks Fills the Dead Cone
We calculate the transverse momentum dependence of the medium-induced gluon
energy distribution radiated off massive quarks in spatially extended QCD
matter. In the absence of a medium, the distribution shows a characteristic
mass-dependent depletion of the gluon radiation for angles smaller than m/E,
the so-called dead cone effect. Medium-modifications of this spectrum are
calculated as a function of quark mass, initial quark energy, in-medium
pathlength and density. Generically, medium-induced gluon radiation is found to
fill the dead cone, but it is reduced at large gluon energies compared to the
radiation off light quarks. We quantify the resulting mass-dependence for
momentum-averaged quantities (gluon energy distribution and average parton
energy loss), compare it to simple approximation schemes and discuss its
observable consequences for nucleus-nucleus collisions at RHIC and LHC. In
particular, our analysis does not favor the complete disappearance of energy
loss effects from leading open charm spectra at RHIC.Comment: 27 pages LaTeX, 15 eps-figure
Bayesian reweighting of nuclear PDFs and constraints from proton-lead collisions at the LHC
New hard-scattering measurements from the LHC proton-lead run have the
potential to provide important constraints on the nuclear parton distributions
and thus contributing to a better understanding of the initial state in heavy
ion collisions. In order to quantify these constraints, as well as to assess
the compatibility with available nuclear data from fixed target experiments and
from RHIC, the traditional strategy is to perform a global fit of nuclear PDFs.
This procedure is however time consuming and technically challenging, and
moreover can only be performed by the PDF fitters themselves. In the case of
proton PDFs, an alternative approach has been suggested that uses Bayesian
inference to propagate the effects of new data into the PDFs without the need
of refitting. In this work, we apply this reweighting procedure to study the
impact on nuclear PDFs of low-mass Drell-Yan and single-inclusive
hadroproduction pseudo-data from proton-lead collisions at the LHC as
representative examples. In the hadroproduction case, in addition we assess the
possibility of discriminating between the DGLAP and CGC production frameworks.
We find that the LHC proton-lead data could lead to a substantial reduction of
the uncertainties on nuclear PDFs, in particular for the small-x gluon PDF
where uncertainties could decrease by up to a factor two. The Monte Carlo
replicas of EPS09 used in the analysis are released as a public code for
general use. It can be directly used, in particular, by the experimental
collaborations to check, in a straightforward manner, the degree of
compatibility of the new data with the global nPDF analyses.Comment: 21 pages, 10 figure
The Pittsburgh Sloan Digital Sky Survey MgII Quasar Absorption-Line Survey Catalog
We present a catalog of intervening MgII quasar absorption-line systems in
the redshift interval 0.36 <= z <= 2.28. The catalog was built from Sloan
Digital Sky Survey Data Release Four (SDSS DR4) quasar spectra. Currently, the
catalog contains > 17,000 measured MgII doublets. We also present data on the
~44,600 quasar spectra which were searched to construct the catalog, including
redshift and magnitude information, continuum-normalized spectra, and
corresponding arrays of redshift-dependent minimum rest equivalent widths
detectable at our confidence threshold. The catalog is available on the web. A
careful second search of 500 random spectra indicated that, for every 100
spectra searched, approximately one significant MgII system was accidentally
rejected. Current plans to expand the catalog beyond DR4 quasars are discussed.
Many MgII absorbers are known to be associated with galaxies. Therefore, the
combination of large size and well understood statistics makes this catalog
ideal for precision studies of the low-ionization and neutral gas regions
associated with galaxies at low to moderate redshift. An analysis of the
statistics of MgII absorbers using this catalog will be presented in a
subsequent paper.Comment: AJ, in pres
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