19,291 research outputs found
Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers
Single gap (gas gap 2 mm) bakelite Resistive Plate Chamber (RPC) modules of
various sizes from 10 cm \times 10 cm to 1 m \times 1 m have been fabricated,
characterized and optimized for efficiency and time resolution. Thin layers of
different grades of silicone compound are applied to the inner electrode
surfaces to make them smooth and also to reduce the surface resistivity. In the
silicone coated RPCs an efficiency > 90% and time resolution \sim 2 ns (FWHM)
have been obtained for both the streamer and the avalanche mode of operation.
Before fabrication of detectors the electrical properties such as bulk
resistivity and surface resistivity of the electrode materials are measured
carefully. Effectiveness of different silicone coating in modifying the surface
resistivity was evaluated by an instrument developed for monitoring the I-V
curve of a high resistive surface. The results indicate definite correlation of
the detector efficiency for the atmospheric muons and the RPC noise rates with
the surface resistivity and its variation with the applied bias voltage. It was
also found that the surface resistivity varies for different grades of silicone
material applied as coating, and the results are found to be consistent with
the detector efficiency and noise rate measurements done with these RPCs.Comment: 9 Pages, 6 figure
Measurement of electrical properties of electrode materials for the bakelite Resistive Plate Chambers
Single gap (gas gap 2 mm) bakelite Resistive Plate Chamber (RPC) modules of
various sizes from 10 cm \times 10 cm to 1 m \times 1 m have been fabricated,
characterized and optimized for efficiency and time resolution. Thin layers of
different grades of silicone compound are applied to the inner electrode
surfaces to make them smooth and also to reduce the surface resistivity. In the
silicone coated RPCs an efficiency > 90% and time resolution \sim 2 ns (FWHM)
have been obtained for both the streamer and the avalanche mode of operation.
Before fabrication of detectors the electrical properties such as bulk
resistivity and surface resistivity of the electrode materials are measured
carefully. Effectiveness of different silicone coating in modifying the surface
resistivity was evaluated by an instrument developed for monitoring the I-V
curve of a high resistive surface. The results indicate definite correlation of
the detector efficiency for the atmospheric muons and the RPC noise rates with
the surface resistivity and its variation with the applied bias voltage. It was
also found that the surface resistivity varies for different grades of silicone
material applied as coating, and the results are found to be consistent with
the detector efficiency and noise rate measurements done with these RPCs.Comment: 9 Pages, 6 figure
A Precision Measurement of Electroweak Parameters in Neutrino-Nucleon Scattering
The CCFR collaboration reports a precise measurement of electroweak
parameters derived from the ratio of neutral-current to charged-current
cross-sections in neutrino-nucleon scattering at the Fermilab Tevatron. This
ratio of cross-sections measures the neutral current couplings to quarks, which
implies a determination of sin^2 theta_W (on-shell) = 0.2236 +/- 0.0028(expt.)
+/- 0.0030(model) for m_top=175 GeV, m_Higgs=150 GeV. This is equivalent to
M_W=80.35+/-0.21 GeV. The good agreement of this measurement with Standard
Model expectations implies the exclusion of additional
neutrino-neutrino-quark-quark contact interactions at 95% confidence at a mass
scale of 1-8 TeV, depending on the form of the contact interaction.Comment: formatted in revtex, 5 pages, 3 eps figures included via psfig,
submitted to Physical Review Letter
New Results From CLEO and BES
Latest experimental results from BES in the charmonium mass region, and those
from CLEO in the bottomonium and charmonium spectroscopy are reviewed.Comment: 12 pages, 12 figures, Presented at First Meeting of the APS Topical
Group on Hadron Physics, Fermilab, Batavia, Illinois, Oct 24-26, 200
Search for X(3872) in gamma gamma Fusion and ISR at CLEO
We report on a search for the X(3872) state using 15.1 fb^{-1} of e+ e-
annihilation data taken with the CLEO III detector in the sqrt{s} = 9.46-11.30
GeV region. Separate searches for the production of X(3872) in untagged gamma
gamma fusion and e+ e- annihilation following initial state radiation are made
by taking advantage of the unique correlation of J/psi -> l+ l- in X(3872)
decay into J/psi pi+ pi-. No signals are observed in either case, and 90%
confidence upper limits are established as (2J+1)Gamma_{gammagamma}(X(3872))B(X
-> J/psi pi+ pi-) J/psi pi+ pi-) < 8.3
eV.Comment: 4 pages, 2 figures, to appear in the proceedings of the 1st Meeting
of the APS Topical Group on Hadronic Physics, Fermilab, Oct. 24-26, 200
Correlations and fluctuations studied with ALICE
The measurement of particle correlations and event-by-event fluctuations of
physical observables allows to study a large variety of properties of the
matter produced in ultra relativistic heavy-ion collisions. We will present
results for two-particle correlations, mean transverse momentum fluctuations,
and net charge fluctuations in Pb-Pb collisions at 2.76 TeV.Comment: 7 pages, 5 figures, Proceedings submitted for the 28th Winter
Workshop on Nuclear Dynamics, Puerto Rico, April 7-14, 2012; corrected typo
Event anisotropy of identified , photon and electron compared to charged , , and deuteron in = 200 GeV Au+Au at PHENIX
We report the recent results of event anisotropy analysis focused on in
= 200 GeV Au+Au collisions at PHENIX.Comment: 4 pages, 3 figures, contribution to the proceedings of the 17th
International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions
(Quark Matter, Oakland, January 11-17, 2004). To appear in the proceedings
(Journal of Physics G
New developments in the statistical approach of parton distributions
We recall how parton distributions are constructed in a statistical physical
picture of the nucleon. The chiral properties of QCD lead to strong relations
between quarks and antiquarks distributions and the importance of the Pauli
exclusion principle is also emphasized. A global next-to-leading order QCD
analysis of unpolarized and polarized deep-inelastic scattering data allows to
determine a small number of free parameters. Some predictions are compared to
recent experimental results and we discuss the prospects of this physical
framework.Comment: 10 pages, 12 figures. Invited talk presented at the " Corfu Summer
Institute on EPP,CORFU2005, Corfu, Greece, September 4-26, 2005. To be
published in Journal of Physics, Conference Series (2006
Charged particle jet measurements with the ALICE experiment in proton-proton collisions at the LHC
We present preliminary results of measurements of charged particle jet
properties in proton-proton collisions at = 7 TeV using the ALICE
detector. Jets are reconstructed using and SISCone jet
finding algorithms with resolution parameter in the range of transverse
momentum from 20 to 100 GeV/ in the midrapidity region
(\mid\eta\mid\textless 0.5). The uncorrected charged jet spectra obtained
using the three different jet finders show good agreement. The data are
compared to predictions from PYTHIA-Perugia0, PYTHIA-Perugia2011, and PHOJET.
The mean charged particle multiplicity in leading jets increases with
increasing jet and is consistent with model predictions. The radial
distributions of transverse momentum about the jet direction and the
distributions of the average radius containing 80% of the total jet
found in the jet cone ( in this analysis), indicate that high jets are more collimated than low jets.Comment: 6 pages, 6 figures, Conference Proceedings submitted for the 28th
Winter Workshop on Nuclear Dynamics, Puerto Rico, April 7-14, 201
New Particles from Belle
I report recent results on hidden charm spectroscopy from Belle. These
include: observation of a near-threshold enhancement in the omega-J/psi
invariant mass distribution for exclusive B-->K omega J/psi decays; evidence
for the decay X(3872)-->pi+pi-pi0 J/psi, where the pi+pi-pi0 invariant mass
distribution has a strong peak between 750 MeV and the kinematic limit of 775
MeV, suggesting that the process is dominated by the sub-threshold decay
X-->omega J/psi; and the observation of a peak near 3940 MeV in the J/psi
recoil mass spectrum for the inclusive continuum process e+e- --> J/psi X. The
results are based on a study of a 287 fb-1 sample of e+e- annihilation data
collected at center- of-mass energies around the Upsilon(4S) in the Belle
detector at the KEKB collider.Comment: 10 pages 12 figures. Invited talk at the 1st meeting of the APS
Topical Group on Hadronic Physics, Fermilab, October 24-26, 2004; revised to
correct some reference
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