Search

Dark sectors charged under a new Abelian interaction have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon (A'), connecting the dark sector to the standard model. We present a search for a dark photon in the reaction e+e- → γA', A' → e+e- , μ+μ- using 514 fb-1 of data collected with the BABAR detector. We observe no statistically significant deviations from the standard model predictions, and we set 90% confidence level upper limits on the mixing strength between the photon and dark photon at the level of 10-4 - 10-3 for dark photon masses in the range 0.02-10.2 GeV. We further constrain the range of the parameter space favored by interpretations of the discrepancy between the calculated and measured anomalous magnetic moment of the muon. [ABSTRACT FROM AUTHOR]

Abstract: Triple GEM chamber has been selected to be used for the muon detection system (MUCH) in the Compressed Baryonic Matter (CBM) experiment at the upcoming Facility for the Antiproton and Ion Research (FAIR). Two prototype triple-GEM chambers filled with the mixture of argon and CO2 gases in the ratio of 70:30 were made of small-size (10cm×10cm) single-mask GEM foils and read by a self-triggered readout ASIC called nXYTER have been tested with pion beams at CERN. The readout electronics records the arrival times of GEM hits and of corresponding coincidence trigger signals separately. The distribution of time difference between GEM hits and respective triggers shows a peak demonstrating the time correlation between GEM hits and the trigger. The width (σ) of the time-correlation peak, which is related to the time resolution of the chamber, reduces with voltage approaching ns at of 335V. Considering the hits inside the time-correlation peak to correspond to the beam trigger, the efficiency reaches a plateau at 95% at above 330V. For a readout plane segmented by 3mm×3mm pads, on an average 1.2 pads are fired per trigger for pion beams at the operating voltage. The chamber shows a gain of at of 350V. [Copyright &y& Elsevier]

In this work, we summarize the development and current status of the Global Muon Detector Network (GMDN). The GMDN started in 1992 with only two muon detectors. It has consisted of four detectors since the Kuwait-city muon hodoscope detector was installed in March 2006. The present network has a total of 60 directional channels with an improved coverage of the sunward Interplanetary Magnetic Field (IMF) orientation, making it possible to continuously monitor cosmic ray precursors of geomagnetic storms. The data analysis methods developed also permit precise calculation of the three dimensional cosmic ray anisotropy on an hourly basis free from the atmospheric temperature effect and analysis of the cosmic ray precursors free from the diurnal anisotropy of the cosmic ray intensity. [ABSTRACT FROM AUTHOR]

A search for heavy Majorana neutrinos produced in the B–→π+μ–μ– decay mode is performed using 3  fb−1 of integrated luminosity collected with the LHCb detector in pp collisions at center-of-mass energies of 7 and 8 TeV at the LHC. Neutrinos with masses in the range 250 to 5000 MeV and lifetimes from zero to 1000 ps are probed. In the absence of a signal, upper limits are set on the branching fraction B(B–→π+μ–μ–) as functions of neutrino mass and lifetime. These limits are on the order of 10–9 for short neutrino lifetimes of 1 ps or less. Limits are also set on the coupling between the muon and a possible fourth-generation neutrino. [ABSTRACT FROM AUTHOR]

Abstract: LHAASO (Large High Altitude Air Shower Observatory) is a large project to research on high energy gamma ray astronomy and cosmic ray physics. KM2A (one KM 2 Array), one main part of the LHAASO project, using a 1km 2 array composed of electron detectors (ED) and muon detectors (MD), focuses on gamma ray astronomy above 30TeV and cosmic ray physics in the “knee” region. Accurate measurement of gamma ray energy spectra above 30TeV is crucial to identify the sources as the galactic cosmic ray accelerators. Monte Carlo simulation indicates that cosmic gamma rays can be distinguished from cosmic nuclei background by using muon content in extensive air showers (EAS). With the sensitivity of about 1% of the integral flux of Crab Nebula, the high duty cycle of at least 90 and the full sky survey, the KM2A array would be very useful in discovering the galactic gamma ray sources and identifying the cosmic ray sources with gamma-ray emission. A detailed simulation is carried out for studying performance and expectation of the KM2A array in gamma ray astronomy above 30TeV. [Copyright &y& Elsevier]

Abstract: In a modern remake of the historical main balloon flight of Victor Hess, a group of private scientists reached an altitude of 6.000m onboard of a balloon, taking measures by a series of home-made muon detectors. [Copyright &y& Elsevier]