30,536 research outputs found
Pentaquarks in high-energy colliding experiments: perspectives from HERA
Several issues related to pentaquark searches relevant for current and future
high-energy colliding experiments are discussed. We make an attempt to explain
why pentaquark candidates are not seen by some experiments, and what makes the
HERA experiments so special in such searches.Comment: 14 pages, 4 eps figure
CMS reconstruction improvement for the muon tracking by the RPC chambers
The contribution of Resistive Plate Chamber (RPC) to muon reconstruction in
CMS has been studied on a sample of muons collected in proton-proton collisions
at sqrt(s) = 7 TeV at the LHC in 2011. Muon reconstruction is performed using
the all-silicon inner tracker and with up to four stations of gas-ionization
muon detectors. Drift Tubes and Cathode Strip Chambers detect muons in the
barrel and endcap regions, respectively, and are complemented by the RPC
system. Measured distributions of reconstructed hits in the RPCs crossed by
muons from Z decays with a transverse momentum pT above 20 GeV/c are well
reproduced by the Monte Carlo simulation. From the samples of J/psi and Z
events, the efficiencies for muons with and without the inclusion of the RPC
hits in the muon track reconstruction are measured and compared with the
simulation. Using RPC information in track reconstruction improves up to about
3% of offline reconstruction efficiency for the muons in the region of pT above
7 GeV/c, in good agreement with simulation.Comment: Presented by Minsuk Kim at the XI workshop on Resistive Plate
Chambers and Related Detectors - RPC2012, INFN Laboratori Nazionali di
Frascati Italy, February 5-10, 201
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
Strangeness and heavy flavor at RHIC: Recent results from PHENIX
We report recent results of strangeness and heavy flavor measurements from
PHENIX.
The topics are: Elliptic flow of strangeness and heavy flavor electron
production comparing to the other hadrons, meson production, and an
exotic particle search.Comment: 8 pages, 6 figures, 1 table. Submitted to J. Phys. G (Proceedings of
the 8th International Conference on Strangeness in Quark Matter, Cape Town,
South Africa, September 15-20, 2004
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
Open Charm Production at HERA
Measurements of charmed particle cross sections at HERA in the
photoproduction and deep inelastic regimes are reviewed. The status of the
comparison with perturbative QCD calculations is discussed.Comment: Presented at the Ringberg Workshop on ``New Trends in HERA Physics
2001'' 17-22 June 2001. 12 pages, 11 figure
A new gamma*-p / pbar-p factorization test in diffraction, valid below Q^2 about 6 GeV^2
One of the key experimental issues in high energy hadron physics is the
extent to which data from the diffractive interaction mechanism may be
described by a factorized formula which is the product of a universal term
describing the probability of finding a Pomeron in a proton (loosely referred
to as the "Pomeron flux-factor") and a term decribing the Pomeron's interaction
with the other incident proton. In the present paper, after demonstrating that
existing data on diffractive gamma*-p and pbar-p interactions show that the
Pomeron flux-factor is not universal, we present the results of a new test of
factorization in these interactions which does not rely on universality of the
flux-factor. The test is satisfied to within ~20% for 1 < Q^2 ~ 6 GeV^2 and
beta < 0.2 in the gamma*-p interactions, suggesting that the resons for
non-universality of the flux-factor have a limited effect on the factorization
itself. However, a clear breakdown of this test is observed at larger Q^2.
Kharzeev and Levin suggest that this can be attributed to the onset of QCD
evolution effects in the Pomeron's structure. The breakdown occurs in a Q^2
region which agrees with their estimates of a small Pomeron size.Comment: 20 pages, 7 Encapsulated Postscript figures, LaTex, submitted to
European Phisical Journal
Excitation functions of baryon anomaly and freeze-out properties at RHIC-PHENIX
The intermediate region (2 - 5 GeV/) in central Au+Au collisions at
RHIC has a rich physics content. The (anti)proton to pion ratio at the
intermediate gives us a powerful tool to investigate the bulk properties
of the hot and dense matter created at RHIC and their hadronization processes.
We present the preliminary results of identified charged hadron spectra at the
lower beam energies at RHIC. The excitation function of (anti)proton to pion
ratios from SPS to RHIC are shown. We also discuss the onset of the baryon
enhancement at the high energy heavy ion collisions.Comment: 4 pages, 3 figures, Quark Matter 2006 conference proceeding
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