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

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