119920067
An antimatter spectrometer in space
Abstract We discuss a simple magnetic spectrometer to be installed on a satellite or space station. The purpose of this spectrometer is to search for primordial antimatter to the level of antimatter/matter ≈10 −9 , improving the existing limits obtained with balloon flights by a factor of 10 4 to 10 5 . The design of the spectrometer is based on an iron-free, NdFeB permanent magnet, scintillation counters, drift tubes, and silicon or time projection chambers. Different design options are discussed. Typically, the spectrometer has a weight of about 2 tons and an acceptance of about 1.0 m 2 sr. The availability of the new NdFeB material makes it possible for the first time to put a magnet into space economically and reliably.
56005177
Inclusive J production in Z0 decays
Abstract Inclusive J production in Z0 decays is observed via the leptonic decay mode J → l+l− (l = e,μ). We measure the branching ratio Br(Z0 → J + X) = (4.1 ± 0.7 (stat.) ± 0.3 (sys.)) × 10−3. We have calculated the fraction of the J mesons from b-hadron decay and find a branching ratio of Br(b → J + X)= (1.3±0.2(stat.)±0.2(sys.)) × 10−2. We determine the average fractional energy of bottom hadrons 〈XE > = 0.70±0.03 (stat.)+0.02−0.01 (sys.) using the momentum spectrum of the J mesons. From a study of the angle between the J and the most energetic jet, we set an upper limit on the branching ratio Br ( Z 0 → q q g ∗ ; g ∗ → J + X ) −4 at 90% confidence level.
118039047
Physics of tau and charm
The physics of tau and charm started in early 70's after J/$\psi$ and $\tau$ were discovered. Since then several dedicated accelerators and experiments were built with increasing luminosities and studies on light hadron spectroscopy, charmonium, electroweak and QCD were never interupted. New interests and surprises are not rare in this area. With the newly built BEPCII/BESIII, an even brighter future is foreseen.
122214277
A water Cherenkov calorimeter for long baseline neutrino oscillation experiments
Abstract We propose a water-based large homogeneous calorimeter as the next generation neutrino detector for ν factories and/or conventional ν beams. The Cherenkov light produced in water is sufficient to have good energy resolution, and the pattern recognition is realized by a modular water tank structure. Monte Carlo simulations show that the detector performance is excellent for identifying neutrino CC events while rejecting backgrounds.
125677069
TUBE CHAMBERS FOR THE MUON FILTER OF THE L3 DETECTOR
18893994
The mass production and quality control of RPCs for the Daya Bay experiment
Abstract Resistive plate chambers will be used in the Daya Bay reactor neutrino experiment to help veto backgrounds created by cosmic-ray muons. The mass production of RPCs began in 2008 and by the end of 2009, 1600 RPCs (3500 m 2 ) had been produced and tested. This paper describes the production and quality control procedures, and quality assurance using cosmic-ray testing.
122101803
First results on the hybrid photodiode tube
Abstract The performance of a new breed of light detectors based on a photocathode followed by a planar silicon diode working in the bombarding mode is reported. This detector was developed by the LAA project in order to produce a fast light detector capable of covering a span of the more than 4 orders of magnitude of linearity required by the scintillating fibre and lead (“spaghetti”) calorimeter. Linear signals from single, to more than 10 6 photoelectrons per pulse were measured. The general characteristics of this detector are reported here.
110710115
Readout electronics of the ALICE photon spectrometer
The photon spectrometer (PHOS) in the ALICE experiment at LHC is a PbWO4 crystal based electromagnetic calorimeter, dedicated to measuring photons, π°'s and η's over a broad pT range from about 100 MeV/c to 100 GeV/c with the best possible energy and position resolution. The front-end electronics of the PHOS is thus required to cover a large dynamic range, to achieve a timing resolution better than ~ 2 ns in order to discriminate against 1-2 GeV/c (anti-)neutrons, and to provide high pT trigger to select rare high pT events. In this paper, we present the full PHOS readout system, including the avalanche photo-diode, the low noise charge sensitive preamplifier, the 32 channel front-end electronics card, the trigger region unit and the trigger OR module. Results from PHOS commissioning with beam particles and cosmic rays will also be presented to address the performance of the PHOS readout electronics.
117346945
Population study for gamma-ray pulsars: (III) Radiation characteristics and viewing geometry
We have performed a Monte-Calro simulation for Galactic population of pulsars and for the $\gamma$-ray observations. We apply outer gap model for the $\gamma$-ray emission process, and study the radiation characteristics as a function of the magnetic inclination angle $(\alpha)$ and the Earth viewing angle ($\zeta$). In our model, the $\gamma$-ray flux and the spectral cut-off energy tend to decrease as the inclination and viewing angles deviate from $90^{\circ}$. The emerging spectrum above 100 MeV becomes soft with a photon index $p\sim 1.8-2$ for $\zeta \rightarrow 90^{\circ}$ and $p\sim 1.2-1.3$ for $\zeta \ll 90^{\circ}$. Our simulation predicts that the pulsars with larger inclination angles ($\alpha=70-90^{\circ}$) and larger viewing angles ($\zeta=70-90^{\circ}$) have been preferentially detected by the $Fermi$ $\gamma$-ray telescope, and hence the observed pulse profiles of the $\gamma$-ray pulsars have the double peak structure rather than single peak. In the simulation, most $\gamma$-ray millisecond pulsars are categorized as the radio-quiet $\gamma$-ray pulsars, because its radio fluxes are under the sensitivities of the major radio surveys. Even we drastically increase the radio sensitivity by a factor of ten, the number of radio-selected millisecond pulsars detected by the $Fermi$ ten years observations is still much less than the expected $\gamma$-ray-selected millisecond pulsars, indicating the radio-quiet millisecond pulsars must contribute to the $Fermi$ unidentified sources and/or the $\gamma$-ray background radiations. The Unique radiation properties of the low-efficient $\gamma$-ray pulsar, PSR J0659+1414, can be explained by the present our gap model with a viewing geometry of $\alpha\sim \zeta=40^{\circ}-50^{\circ}$.
121868996
Development of multi-gap resistive plate chambers with low-resistive silicate glass electrodes for operation at high particle fluxes and large transported charges
Abstract Using electrodes made of semi-conductive glass is an innovative way of improving the rate capability of resistive plate chambers. To address this issue, we developed 6- and 10-gap counters with low-resistive silicate glass electrodes (bulk resistivity ∼10 10  Ω cm) suited for time-of-flight (TOF) applications at high rates and high transported charges. Measurements were performed at GSI-Darmstadt under uniform an irradiation by secondary particles stemming from proton reactions at 2.5 GeV/A. For the 10-gap MRPC, time resolutions below 90 ps and efficiencies larger than 90% were obtained at counting rates up to 25 kHz/cm 2 . When the particle flux increases every 5 kHz/cm 2 , the efficiency decreases by 1% and the time resolution deteriorates by 4 ps. A tolerable decrease of the material conductivity was also observed for a total transported charge of 1 C/cm 2 .
59042296
Vacuum chamber and crotch absorber for the SPring-8 storage ring vacuum system
The whole vacuum system for the SPring-8 storage ring is planning to be completely installed in the ring by October 1996. The vacuum chamber for the straight sections consists of a beam chamber and a slot-isolated antechamber in which NEG strips are installed To suppress the chamber deformation at the BPM station due to the pressure difference between the atmospheric pressure and the vacuum, ribs are mounted on the chamber In the bending magnet chamber, a distributed ion pump is also installed. The crotch and absorber have been designed to reduce their RF impedances and the radiation level outside the vacuum chamber. In this paper we present details of the final design for the vacuum chamber, crotch and absorber. The chamber supporting system and the structure of ribs are also described.<<ETX>>