Chen Hong-Fang

The Statistical Origin of Constituent-Quark Scaling in QGP Hadronization

Nonextensive statistics in a blast-wave model is implemented to describe the identified hadron production in relativistic p+p and nucleus-nucleus collisions. Incorporating the core and corona components within the TBW formalism allows us to describe simultaneously some of the major observations in hadronic observables at the Relativistic Heavy-Ion Collider (RHIC): the amount of constituent quark scaling (NCQ), the large radial and elliptic flow, the effect of gluon saturation, and the suppression of hadron production at high transverse momentum (pT) due to jet quenching. In this formalism, the NCQ scaling at the RHIC appears as a consequence of a non-equilibrium process. Our study also provides concise reference distributions with a least χ2 fit of the available experimental data for future experiments and models.

A prototype MRPC beam test for the BESIII ETOF upgrade

A prototype multi-gap resistive plate chamber (MRPC) with a 2×6 gap structure is developed for the upgrading of the endcap time-of-flight (ETOF) detector in the Beijing Spectrometer (BESIII). The prototype MRPC is tested in the E3 beam line of the Beijing Electron Positron Collider (BEPC) with secondary charged particles (π and p, etc) of 600 MeV/c. The test results show that the time resolution of the MRPC can reach 50 ps and that the detection efficiency is greater than 98%.

Time calibration for the end cap TOF system of BESIII

The time calibration for end cap TOF system of BESIII is studied in this paper. It has achieved about 110 ps time resolution for muons in dimu events. The pulse height correction using electronic scan curve and the predicted time calculated using Kalman filter method are introduced. This paper also describes the study of using electrons and muons as calibration samples.

Simulation study for a single TOF scintillator using GEANT4

A time-of-flight (TOF) detector system based on plastic scintillators will be used in the Beijing spectrometer III (BSE-III) at Beijing Electron Positron Collider. In this note the result of a detailed Monte Carlo simulation for single TOF scintillator modules, based on GEANT4, is presented. The intrinsic time resolution is obtained. Also given is a comparison of two kinds of plastic scintillation material—BC404 and BC408 of different thicknesses, coupling mode with PMT and geometry. These simulation results could serve as an important guide for the BES-III TOF design.

Self-quenching streamer discharge under extremely large amounts of quenching gas

Abstract The self-quenching streamer mode behaviors appear in both pure carbon dioxide and pure methane filling gas. In pure ethane and pure propane we saw the large saturated pulses, but no transition at any attainable voltage. When the carbon dioxide concentration is larger than 98% in argon-carbon dioxide mixtures, Q trl increases with the concentration.

Time characteristics of a self quenching streamer in the coexistence region

Abstract Experimental studies on the time correlation between electrical signals in the primary avalanche and optical signals which are emitted in the avalanches of the limited proportional mode and the self quenching streamer (SQS) mode have demonstrated that there exists a weak optical emission which is almost simultaneous with the limited proportional avalanche, that a streamer pulse in the SQS mode has a few nanoseconds delay relative to the primary avalanche, and that the spread of the delay (FWHM) is also a few nanoseconds.

A large-area GEM detector using a novel self-stretching technique

A Gas Electron Multiplier (GEM) detector with an effective area of 300 mm×300 mm has been constructed using a novel self-stretching technique, which allows a highly flexible and efficient GEM detector assembly free of glue or spacers. This makes the re-opening and repair of the GEM detectors possible and significantly reduces the scrap rate in the mass production of large-area GEM detectors. With the technique, the assembly time can be limited to a few hours, a factor of ten improvement compared to that using gluing techniques. The details of design and assembly procedure of the 300 mm×300 mm GEM detector are described in this paper. This detector was tested with 8 keV X-rays for the effective gain, energy resolution and performance uniformity. The results show that the typical energy resolution is 20% at an effective gain of about 104, with fairly good uniformity.

Prospects for searching the η→e+e− rare decay at the CSR

We study the possibility of searching the η→e+e− rare decay on the Cooling Storage Ring (CSR) at Lanzhou. The main features of the proposed Internal Target Experiment (ITE) and External Target Facility (ETF) are included in the Monte Carlo simulation. Both the beam condition at the CSR and the major physics backgrounds are carefully taken into account. We conclude that the ITE is more suitable for such a study due to better detector acceptance and higher beam density. At the maximum designed luminosity (1034 cm−2 s−1), η→e+e− events can be collected every ~400 seconds at the CSR. With a mass resolution of 1 MeV, the expected signal-to-background (S/B) ratio is around 1.

Pulse shape of the self quenching streamer counter in the coexistence region

Abstract The pulse shape of the electrical signal out of the counter operating in the self-quenching streamer (SQS) mode is obtained and the time correlation between the primary avalanche and the SQS avalanche is measured and studied. The results yield more information in the coexistence region about the time jitters in the process of the SQS avalanche than that shown in our last paper. [Han Jiaxiang et al., Nucl. Instr. and Meth. A 349 (1994) 495].

A cosmic ray test platform based on high time resolution MRPC technology

In order to test the performance of detector prototypes in a laboratory environment, we design and build a large area (90 cm×52 cm) test platform for cosmic rays based on a well-designed Multi-gap Resistive Plate Chamber (MRPC) with excellent time resolution and a high detection efficiency for minimum ionizing particles. The time resolution of the MRPC module used is tested to be ~80 ps, and the position resolution along the strip is ~5 mm, while the position resolution perpendicular to the strip is ~12.7 mm. The platform constructed by four MRPC modules can be used for tracking cosmic rays with a spatial resolution of ~6.3 mm, and provide a reference time ~40 ps.