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 possible signature of new physics at BES-III

The recent observations of the purely leptonic decay \Ds \to \mu^+ \nu_{\mu} and $\tau^+\nu_{\tau}$ at CLEO-c and $B$ factory may allow a possible contribution from a charged Higgs boson. One such measurement of the decay constant $f_{D_s}$ differs from the most precise unquenched lattice QCD calculation by 4 $\sigma$ level. Meanwhile, the measured ratio, {\cal BR}(\Ds \to \mu^+ \nu_{\mu}) / {\cal BR}(\Dp \to \mu^+ \nu_{\mu}), is larger than the standard model prediction at 2.0$\sigma$ level. We discuss that the precise measurement of the ratio {\cal BR}(\Ds \to \mu^+ \nu_{\mu}) / {\cal BR}(\Dp \to \mu^+ \nu_{\mu}) at BES-III will shed light on the presence of new intermediate particles by comparing the theoretical predictions, especially, the predictions of high precise unquenched lattice QCD calculation.Comment: 5 pages, 3 figures, mini-review, accepted by Chinese Physics C (HEP & NP

Evidence for the decays of Lambda(+)(C) -> Sigma(+) eta and Sigma(+) eta '

WOS: 000475778100002We study the hadronic decays of Lambda(+)(C) to the final states Sigma(+) eta and Sigma(+) eta', using an e(+) e(-) annihilation data sample of 567 pb(-1) taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCII collider. We find evidence for the decays Lambda(+)(C) -> Sigma(+) eta and Sigma(+) eta' with statistical significance of and, respectively. Normalizing to the reference decays Lambda(+)(C) -> Sigma(+) pi(0) and Sigma(+) omega, we obtain the ratios of the branching fractions B(Lambda(+)(C) -> Sigma(+) eta)/B(Lambda(+)(C) -> Sigma(+) pi(0)) and B(Lambda(+)(C) -> Sigma(+) eta')/B(Lambda(+)(C) -> Sigma(+) omega) to be 0.35 +/- 0.16 +/- 0.02 and 0.86 +/- 0.34 +/- 0.04, respectively. The upper limits at the 90% confidence level are set to be B(Lambda(+)(C) -> Sigma(+) eta)/B(Lambda(+)(C) -> Sigma(+) pi(0)) Sigma(+) eta')/B(Lambda(+)(C) -> Sigma(+) omega) Sigma(+) eta) = (0.41 +/- 0.19 +/- 0.05)% ( Sigma(+) eta') = (1.34 +/- 0.53 +/- 0.19)% ( Sigma(+) eta is consistent with the previous measurement, and the branching fraction of Lambda(+)(C) -> Sigma(+) eta' is measured for the first time.National Key Basic Research Program of China [2015CB856700]; National Natural Science Foundation of China (NSFC) [11235011, 11275266, 11335008, 11425524, 11625523, 11635010]; Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; CAS Center for Excellence in Particle Physics (CCEPP); NSFC [U1332201, U1532257, U1532258]; CAS [U1332201, U1532257, U1532258, KJCX2-YW-N29, KJCX2-YW-N45, QYZDJ-SSW-SLH003]; 100 Talents Program of CAS; National 1000 Talents Program of China; INPAC; Shanghai Key Laboratory for Particle Physics and Cosmology; German Research Foundation DFG (Collaborative Research Center CRC 1044) [FOR 2359]; Istituto Nazionale di Fisica Nucleare, Italy; Koninklijke Nederlandse Akademie van Wetenschappen (KNAW) [530-4CDP03]; Ministry of Development of Turkey [DPT2006K-120470]; National Science and Technology fund; Swedish Research Council; U.S. Department of Energy [DE-FG02-05ER41374, DE-SC-0010118, DE-SC-0010504, DE-SC-0012069]; University of Groningen (RuG); Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI), Darmstadt; WCU Program of National Research Foundation of Korea [R32-2008-000-10155-0]Supported in part by National Key Basic Research Program of China (2015CB856700); National Natural Science Foundation of China (NSFC)(11235011, 11275266, 11335008, 11425524, 11625523, 11635010); the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; the CAS Center for Excellence in Particle Physics (CCEPP); Joint Large-Scale Scientific Facility Funds of the NSFC and CAS (U1332201, U1532257, U1532258); CAS (KJCX2-YW-N29, KJCX2-YW-N45, QYZDJ-SSW-SLH003); 100 Talents Program of CAS; National 1000 Talents Program of China; INPAC and Shanghai Key Laboratory for Particle Physics and Cosmology; German Research Foundation DFG (Collaborative Research Center CRC 1044, FOR 2359); Istituto Nazionale di Fisica Nucleare, Italy; Koninklijke Nederlandse Akademie van Wetenschappen (KNAW) (530-4CDP03); Ministry of Development of Turkey (DPT2006K-120470); National Science and Technology fund; The Swedish Research Council; U.S. Department of Energy under (DE-FG02-05ER41374, DE-SC-0010118, DE-SC-0010504, DE-SC-0012069); University of Groningen (RuG) and the Helmholtzzentrum fuer Schwerionenforschung GmbH (GSI), Darmstadt; WCU Program of National Research Foundation of Korea (R32-2008-000-10155-0