2,852 research outputs found
Jet Physics in Heavy Ion Collisions with Compact Muon Solenoid detector at the LHC
The status of CMS jet simulations and physics analysis in heavy ion
collisions is presented. Jet reconstruction and high transverse momentum
particle tracking in the high multiplicity environment of heavy ion collisions
at the LHC using the CMS calorimetry and tracking system are described. The
Monte Carlo tools used to simulate jet quenching are discussed.Comment: Talk given at 5th International Conference on Physics and
Astrophysics of Quark Gluon Plasma, Salt Lake City, Kolkata, India, February
8-12, 2005; 4 pages including 4 figures as EPS-files; prepared using LaTeX
package for Journal of Physics
Hard probes in heavy ion collisions at the LHC: heavy flavour physics
We present the results from the heavy quarks and quarkonia working group.
This report gives benchmark heavy quark and quarkonium cross sections for
and collisions at the LHC against which the rates can be compared in
the study of the quark-gluon plasma. We also provide an assessment of the
theoretical uncertainties in these benchmarks. We then discuss some of the cold
matter effects on quarkonia production, including nuclear absorption,
scattering by produced hadrons, and energy loss in the medium. Hot matter
effects that could reduce the observed quarkonium rates such as color screening
and thermal activation are then discussed. Possible quarkonium enhancement
through coalescence of uncorrelated heavy quarks and antiquarks is also
described. Finally, we discuss the capabilities of the LHC detectors to measure
heavy quarks and quarkonia as well as the Monte Carlo generators used in the
data analysis.Comment: 126 pages Latex; 96 figures included. Subgroup report, to appear in
the CERN Yellow Book of the workshop: Hard Probes in Heavy Ion Collisions at
the LHC. See also http://a.home.cern.ch/f/frixione/www/hvq.html for a version
with better quality for a few plot
Photon Physics in Heavy Ion Collisions at the LHC
Various pion and photon production mechanisms in high-energy nuclear
collisions at RHIC and LHC are discussed. Comparison with RHIC data is done
whenever possible. The prospect of using electromagnetic probes to characterize
quark-gluon plasma formation is assessed.Comment: Writeup of the working group "Photon Physics" for the CERN Yellow
Report on "Hard Probes in Heavy Ion Collisions at the LHC", 134 pages. One
figure added in chapter 5 (comparison with PHENIX data). Some figures and
correponding text corrected in chapter 6 (off-chemical equilibrium thermal
photon rates). Some figures modified in chapter 7 (off-chemical equilibrium
photon rates) and comparison with PHENIX data adde
Observation of exotic meson production in the reaction at 18 GeV/c
An amplitude analysis of an exclusive sample of 5765 events from the reaction
at 18 GeV/c is described. The
production is dominated by natural parity exchange and by
three partial waves: those with and . A
mass-dependent analysis of the partial-wave amplitudes indicates the production
of the meson as well as the meson, observed for the
first time decaying to . The dominant, exotic
(non- partial wave is shown to be resonant with a mass of
GeV/c^2 and a width of GeV/c^2 . This exotic state, the , is produced with a
dependence which is different from that of the meson, indicating
differences between the production mechanisms for the two states.Comment: 5 pages with 4 figure
A partial wave analysis of the system produced in charge exchange collisions
A partial wave analysis of the of the system produced in the
charge exchange reaction: at an incident momentum of
is presented as a function of invariant mass,
, and momentum transfer squared, , from the incident
to the outgoing system.Comment: 24 pages total,8 pages text, 14 figures, 1 table. Submitted to Phys
Rev
Evidence for Exotic J^{PC}=1^{-+} Meson Production in the Reaction pi- p --> eta pi- p at 18 GeV/c
Details of the analysis of the eta pi- system studied in the reaction pi^{-}
p --> eta pi^{-} p at 18 GeV/c are given. Separate analyses for the 2 gamma and
pi+ pi- pi0 decay modes of the eta are presented. An amplitude analysis of the
data indicates the presence of interference between the a(2)(1320)- and a
J^{PC}=1^{-+} wave between 1.2 and 1.6 GeV/c^2. The phase difference between
these waves shows phase motion not attributable solely to the a(2)(1320)-. The
data can be fitted by interference between the a(2)(1320)- and an exotic 1^{-+}
resonance with M = 1370 +-16 +50 -30} MeV/c^2 and Gamma = 385 +- 40 +65 -105
MeV/c^2. Our results are compared with those of other experiments.Comment: 50 pages of text and 34 figure
Debugging Data Transfers in CMS
The CMS experiment at CERN is preparing for LHC data taking in severalcomputing preparation activities. In early 2007 a traffic load generator infrastructure for distributed data transfer tests was designed and deployed to equip the WLCG tiers which support the CMS virtual organization with a means for debugging, load-testing and commissioning data transfer routes among CMS computing centres. The LoadTest is based upon PhEDEx as a reliable, scalable data set replication system. The Debugging Data Transfers (DDT) task force was created to coordinate the debugging of the data transfer links. The task force aimed to commission most crucial transfer routes among CMS tiers by designing and enforcing a clear procedure to debug problematic links. Such procedure aimed to move a link from a debugging phase in a separate and independent environment to a production environment when a set of agreed conditions are achieved for that link. The goal was to deliver one by one working transfer routes to the CMS data operations team. The preparation, activities and experience of the DDT task force within the CMS experiment are discussed. Common technical problems and challenges encountered during the lifetime of the taskforce in debugging data transfer links in CMS are explained and summarized
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