6,403 research outputs found
Recent results on the properties of two-phase argon avalanche detectors
The characteristic properties of two-phase Ar avalanche detectors, including
those obtained with CsI photocathode, are further studied. Such detectors are
relevant in the field of coherent neutrino-nucleus scattering and dark matter
search experiments. The detectors investigated comprised a 1 cm thick liquid Ar
layer followed by a triple-GEM multiplier. In these detectors, typical gains
reaching 10000 were obtained with good reproducibility and a stable operation
for at least one day was demonstrated. Amplitude and pulse-shape
characteristics are presented under irradiation with X-rays, gamma-rays and
neutrons from different radioactive sources. The detection of both primary
scintillation and ionization signals at higher gains, at a deposited energy of
60 keV, has been demonstrated.Comment: 6 pages, 11 figures. Presented at Xth Int. Conf. for Collid. Beam
Phys., Feb 28 - March 6, 2008, Novosibirsk, to be published in Nucl. Instr.
Meth.
Dalitz Analysis of B->K+pi+pi- and B->K+K+pi-
We report results of the Dalitz analysis of the three-body charmless
B->K+pi+pi- and B->K+K+K- decays based on a 140fb^{-1} data sample collected
with the Belle detector. Measurements of branching fractions for quasi-two-body
decays to scalar-pseudoscalar states: B-> f_0(980)K^+, B-> K^*_0(1430)^0 pi+,
and to vector-pseudoscalar states: B-> K^*(892)^0 pi+, B-> rho^0 K+, B-> phi K+
are presented. Upper limits on decays to some pseudoscalar-tensor final states
are reported. We also report the new measurement of the B-> chi_c K+ branching
fraction in two chi_c decay channels: chi_c-> pi+ pi- and chi_c-> K+K-.Comment: ICHEP04 proceedings, 4 pages, 1 figur
Study of ion feedback in multi-GEM structures
We study the feedback of positive ions in triple and quadruple Gas Electron
Multiplier (GEM) detectors. The effects of GEM hole diameter, detector gain,
applied voltages, number of GEMs and other parameters on ion feedback are
investigated in detail. In particular, it was found that the ion feedback is
independent of the gas mixture and the pressure. In the optimized multi-GEM
structure, the ion feedback current can be suppressed down to 0.5% of the anode
current, at a drift field of 0.1 kV/cm and gain of 10^4. A simple model of ion
feedback in multi-GEM structures is suggested. The results obtained are
relevant to the performance of time projection chambers and gas
photomultipliers.Comment: 9 pages, 11 figures. Submitted to Nucl. Instr. and Meth.
High pressure operation of the triple-GEM detector in pure Ne, Ar and Xe
We study the performance of the triple-GEM (Gas Electron Multiplier) detector
in pure noble gases Ne, Ar and Xe, at different pressures varying from 1 to 10
atm. In Ar and Xe, the maximum attainable gain of the detector abruptly drops
down for pressures exceeding 3 atm. In contrast, the maximum gain in Ne was
found to increase with pressure, reaching a value of 100,000 at 7 atm. The
results obtained are of particular interest for developing noble gas-based
cryogenic particle detectors for solar neutrino and dark matter search.Comment: 7 pages, 4 figures. Submitted to Nucl. Instr. and Meth. A as a letter
to the Edito
Infrared scintillation yield in gaseous and liquid argon
The study of primary and secondary scintillations in noble gases and liquids
is of paramount importance to rare-event experiments using noble gas media. In
the present work, the scintillation yield in gaseous and liquid Ar has for the
first time been measured in the near infrared (NIR) and visible region, both
for primary and secondary (proportional) scintillations, using Geiger-mode
avalanche photodiodes (G-APDs) and pulsed X-ray irradiation. The primary
scintillation yield of the fast component was measured to be 17000 photon/MeV
in gaseous Ar in the NIR, in the range of 690-1000 nm, and 510 photon/MeV in
liquid Ar, in the range of 400-1000 nm. Proportional NIR scintillations
(electroluminescence) in gaseous Ar have been also observed; their
amplification parameter at 163 K was measured to be 13 photons per drifting
electron per kV. Possible applications of NIR scintillations in high energy
physics experiments are discussed.Comment: 6 pages, 5 figures. Submitted to Europhysics Letter. Revised Figs. 3
and
Development Of Technological Sour-milk Desserts Enriched With Bifidobacteria
The work is devoted to the development of the technology of fermented sour-milk desserts, enriched with bifidobacteria and biologically active and physiologically valuable substances of fruit-berry raw materials. Bifidobacteria regulate the quality and quantity composition of the normal intestinal microfllora that is an important factor of organism protection from different intestinal infections. The healthy effect is mainly conditioned by biologically valuable properties of specially selected consortiums of lacto- and bifidobacteria, more stable for the effect of inhibitors and unfavorable environmental conditions.At the joint use of selected consortiums of strains of bifido- and lactobacteria, the number of viable cells of bifidobacteria increases in 3-4 times, the antagonistic activity increases comparing with using separate strains of microorganisms.The use of fructose and lactulose as a biostimulating component of sour-milk desserts raises the activity, growth and development of bifidobacteria. For stabilizing the structure of sour-milk clots, there were used hydrocalloids, such as pectin and starch that favors the increase of the number of viable cells of bifidobacteria, provides the necessary viscosity and certain humidity, prevents stratification at using fruit-berry prebiotics. The optimal storage term of sour-milk desserts at temperature (3±1) оС is no more than 15 days
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