17248811
A new surface treatment for the prototype RPCs of the BESIII spectrometer
The prototype resistive plate chambers (RPCs) for the BESIII spectrometer were constructed by using resistive electrodes made from a special type of phenolic paper laminates developed by us. The surface quality of these laminates is superior to other bakelite plates that have been used to construct RPCs elsewhere. A method for adjusting the resistivety of these laminates was also developed. Extensive studies were conducted by using a number of prototype RPCs in the last several years. Tests have shown prototype RPCs made by using our resistive plates without the linseed oil treatment can achieve the level of performance comparable to RPCs with linseed oil treated bakelite or resistive glass electrodes. In this paper, we will discuss the construction of these prototype RPCs. The test results of a prototype RPC that have been monitored for a year will be reported. Based on favorable test results of prototypes, the RPC production for the muon identifier of the BESIII spectrometer has started at the Beijing Gaonengkedi Science and Technology Co. Ltd. in early 2004 using the technology that we developed.
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.
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.
120261584
Overveiw of the BES physics
Recent physics results at Beijing Electron-Positron Collider (BEPC) are reviewed, especially on excited baryons. Substantial improvements are expected at the newly built BESIII experiment, which is operational since 2008. The detector performance is excellent and a total of 100 million Ψ(2S) and 200 million J/Ψ event are collected in 2009. Preliminary results shows that a new era of excited baryon physics will begin.
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.
125677069
TUBE CHAMBERS FOR THE MUON FILTER OF THE L3 DETECTOR
13890255
Some issues concerning holographic dark energy
We study the perturbation of holographic dark energy and find it to be stable. We study the fate of the universe when interacting holographic dark energy is present, and discuss a simple phenomenological classification of the interacting holographic dark energy models. We also discuss the cosmic coincidence problem in the context of holographic dark energy. We find that the coincidence problem cannot be completely solved by adding an interacting term. Inflation may provide a better solution of the coincidence problem.
126253177
Experimental measurement of the mass of the tau lepton at the Beijing Electron Positron Collider (BEPC)
119932492
Fine structure of alpha decay to rotational states of heavy nuclei
To gain a better insight into alpha-decay fine structure, we calculate the relative intensities of alpha decay to 2{sup +} and 4{sup +} rotational states in the framework of the generalized liquid drop model (GLDM) and improved Royer's formula. The calculated relative intensities of alpha decay to 2{sup +} states are in good agreement with the experimental data. For the relative intensities of alpha decay to 4{sup +} states, a good agreement with experimental data is achieved for Th and U isotopes. The formula we obtain is useful for the analysis of experimental data of alpha-decay fine structure. In addition, some predicted relative intensities which are still not measured are provided for future experiments.
110608938
Production of long-strip multi-gap resistive plate chamber module for the STAR-MTD system
A new Long-strip Multi-gap Resistive Plate Chamber (LMRPC) prototype with 5 gas gaps has been developed for the Muon Telescope Detector (MTD) of the STAR experiment at RHIC in order to reduce the working High Voltage (HV) of previous design. Technical specifications related to the final infrastructure present in the experiment have motivated this effort. Its performance has been measured with cosmic rays. The efficiency of this prototype can reach 98% and the time resolution is around 95 ps. It shows a good uniformity among strips. The noise level is less than 0.2 Hz/cm2. The signal transmission and crosstalk of the modules was measured with a vector network analyzer, showing a good match with simulations within the amplifier bandwidth. A new cosmic-ray test system with long scintillators has been developed to accelerate the Quality Control (QC) process during the mass production of STAR-MTD. A selection of perpendicular cosmic-ray events for more accurate evaluation of the time resolution is achieved. The time resolution with this method is better, albeit with larger error, than the result obtained without any selection. A new spacer is used, resulting in a much reduced streamer ratio at comparable fields. Thirty-two modules have been built with the new spacer by the middle of April of 2012. They have been tested and they all have passed the QC.
109049594
Production and quality control of STAR-TOF MRPC
Abstract Multi-gap resistive plate chamber (MRPC) has been adopted to construct the full barrel time-of-flight (TOF) detector for the STAR experiment at RHIC. The cylindrical TOF covers a total area of approximately 64 m 2 and uses 4032 MRPC modules. 70% of the modules were produced in Tsinghua University and the rest were fabricated in University of Science and Technology of China (USTC). In this paper, the production facilities, manufacturing procedures, quality control methods and test results for the Tsinghua MRPC modules are described.