A high time resolution multi—gap resistive plate chamber

Research on a single cell Multi-gap Resistive Plate Chamber(MRPC) was carried out for the Time of Flight detector(TOF) R and D of the STAR experiment .The property of the single chamber was tested with the test beam facility T10 at CERN in Geneva,The MRPC was scanned with the test beam to get the efficiency and time resolution at different position of the active area.The HV plateau was also measured.The time resolution is 65 ps which satisfies the requirement of STAR,The working mechanism of the MRPC is also explained.     

Measurements of momentum correlation and interaction parameters between antiprotons

The two-particle momentum correlation is influenced by the nuclear force between two particles, which has been intensively studied for nucleons and nuclei, but not much for antinucleons or antinuclei. In this pro-ceeding, we present our STAR measurements on momen-tum correlation function of antiproton–antiproton and proton–proton in Au+Au collisions at -------sNN√ =200 GeV at the Relativistic Heavy Ion Collider. Attractive nuclear force between two antiprotons is demonstrated, and the strong interaction parameters (the scattering length and the effective range) are determined. This measurement serves as an additional verification of CPT symmetry. The present information on the strong force in the antiproton–antipro-ton system provides a fundamental ingredient towards understanding the structure of more sophisticated antinuclei.     

Interferometry analyses of pion and kaon for the granular sources for Au+Au collisions at (~SNN)~(1/2)=200 GeV

We examine the interferometry results of identical pion and kaon for the granular sources of quark-gluon plasma droplets for the Au + Au collisions at S_(NN)~(1/2) = 200 GeV.The effects of particle absorptions of pion and kaon on the results are investigated.We find that the absorptions lead to the decrease of the interferometry radii.After considering the absorptions,the interferometry radii of pion and kaon of the granular sources are in better agreement with the experimental data of the Au + Au collisions.     

Interferometry analyses of pion and kaon for the granular sourcesfor Au+Au collisions at -------sNN√ =200 GeV

We examine the interferometry results of identi-cal pion and kaon for the granular sources of quark–gluon plasma droplets for the Au+Au collisions at------sNN√ =200 GeV. The effects of particle absorptions of pion and kaon on the results are investigated. We find that the absorptions lead to the decrease of the interferometry radii. After considering the absorptions, the interferometry radii of pion and kaon of the granular sources are in better agreement with the experimental data of the Au+Au collisions.     

Charm hadron azimuthal angular correlations in Au+Au collisions at ■=200 GeV from parton scatterings

The dynamic evolution of the charm hadron in hot quark matter was studied in the framework of a multiphase transport (AMPT) model.We first reproduced the open charm hadron D_(0pT) spectrum in Au+Au collisions at sNN~(1/2)=200 GeV by triggering the cc production in AMPT,and then the elliptic flow of charm hadrons was described with different parton cascade cross sections.Charm hadron azimuthal angular correlations were proposed,and they are affected by the different parton crosssection parameter applied in the model,which can facilitate our understanding of the loss of collision energy of charm quarks in hot quark medium and can stimulate further experimental studies.     

Alignment calibration and performance study of the STAR PXL detector

We report in this paper the alignment calibration of the STAR pixel detector(PXL) prototype for the RHIC2013 run and performance study of the full PXL detector installed and commissioned in the RHIC 2014 run. PXL detector is the innermost two silicon layers of the STAR heavy flavor tracker aiming at high-precision reconstruction of secondary decay vertex of heavy flavor particles. To achieve the physics goals, the calibration work was done on the detector with high precision. A histogram-based method was successfully applied for the alignment calibration, and the detector efficiency after alignment was studied using both p t p collision data and cosmic ray data.     

200 GeV极化质子对撞产物π0单自旋不对称性

为了解核子自旋结构函数,本文研究了极化质子碰撞过程中介子产物π⁰粒子的单自旋不对称。RHIC/PHENIX Run8数据横动量p_T覆盖范围为1～7 GeV/c,由于质心能量和极化度的大幅提高,其π⁰单自旋不对称度较Run2数据的小3个数量级。π⁰单自旋不对称度随能量和极化度的提高而下降的现象表明胶子Sivers分布得到进一步紧缩,为pQCD的预测结果提供了新的证据。     

Physics performance of the STAR zero degree calorimeter at relativistic heavy ion collider

The zero degree calorimeter (ZDC) at RHIC-STAR was installed in the year 2000. After running for more than 10 years, the performance of the STAR-ZDC cannot maintain a proper status because of the radiation damage. The ZDC on RHIC-BRAHMS had been moved to STAR in 2011 after some tests. We present here the result of the tests as well as the physical performance of those ZDC modules between the 2011 and 2015 RHIC runs. The excellent energy resolution of the ZDC in heavy ion col-lision provides a good candidate for future detector development, such as the CSR experiment at CAS-Lanz-hou facility.     

Mathematical feature of photon spectra produced in ultra—relativistic heavy—ion collision

In 1994 the first single-photon spectra from the 200GeV/A S Au collisions at CERN SPS were reported by WA80 group.Based on these data,it can be proved that as long as there is an instantaneous thermal distribution T(r,t) in an expanding fireball at each instant,the basic mathematical feature of various kinds of photon spectra is that photon yield is approximately an exponential function of the transverse momentum PT in some region,which is basically irrelevant to the uncertainties enclosed in the theoretical estimations.     

电极厚度对MRPC计数率能力的影响

随着加速器亮度的不断提高,对建造TOF系统所需的MRPC探测器的计数率能力的要求也在不断提高。利用DC模型以及二维电阻网络模型,可分析探测器计数率能力随电极厚度的变化关系。本文研究了基于不同电极厚度的MRPC的计数率能力,证实了通过降低电极厚度提高探测器计数率能力的可行性。     

MRPC 宇宙线测试技术研究

采用宇宙线测试系统,同时测量两个空间位置对齐的多气隙电阻板室.采用两种不同的事例挑选方法对两个室的性能进行了分析.结果表明,当选取近乎垂直入射的事例时,MRPC的时间分辨、雪崩信号比例等各项性能均得到提高.还研究了pad间串扰对MRPC性能的影响.     

LHC/ALICE及其光子探测

大型强子对撞机（LHC）上的大型离子对撞机实验（ALICE）将致力于TeV能区重离子碰撞,探测夸克退禁闭的新物质形态——夸克-胶子等离子体（QGP）,探索宇宙诞生之初的物态性质。本文介绍其上的新一代电磁谱仪ALICE光子探测器（PHOS）,它将用于铅-铅碰撞实验中测量直接光子和衰变光子产物,诊断夸克物质的电磁信号。束流测试结果显示,ALICE光子谱仪——PHOS将能够高效探测0.5～100GeV/c的光子。     

MRPC辐照性能试验系统设计

研究MRPC探测器的抗辐照性能,对于RHIC-STAR实验MRPC-TOF的长期稳定运行具有重要意义.设计制作了3.7GBq 60Co γ放射源MRPC辐照性能试验系统,并在两种不同剂量率下进行了辐照实验,得到了MRPC辐照前后的性能变化情况.     

Three dimensional measurement of nanostructures by single event TOF-RBS with nuclear nano probe

Single, double and triple-layer test structures were measured by time of flight (TOF) Rutherford backscattering spectrometry (RBS) for checking the sensitivity and resolution. A single-layer nanostructure with Au stripes on a Si substrate was resolved by TOF-RBS measurement within a short time of 256 s. The spatial resolution, measured by the edge of the Au stripes, was 42 nm. Another single-layer nanostructure with Pt stripes fabricated by electron beam (EB) induced deposition on a Si substrate was resolved by TOF-RBS measurement even at a thickness of Pt stripes less than one mono-layer. Ga embedded layers implanted by a focused ion beam under the Pt stripes fabricated by EB induced deposition on a Si substrate could be detected for a double-layer nanostructure. Furthermore, a triple-layer nanostructure with two Pt stripe layers isolated by a SiO₂ layer fabricated by EB induced deposition on a Si substrate could be resolved and cross-sections shown.     

Single Event Upsets in RAMs Induced by Protons at 4.2 GeV and Protons and Neutrons below 100 MeV

Several different types of random-access-memories (RAMs) have been tested for soft upset susceptibility under a variety of different particle bombardments including thermal neutrons, GeV protons, and protons and neutrons below 100 MeV and with few exceptions found to suffer single event upsets. Devices tested included 4K, 16K and 64K dynamic RAMs and 4K NMOS and 256×4 CMOS static RAMs. Mean upset fluences varied from 106 particles/cm2-upset for 64K dynamic RAMs up to no upsets observed for the 256×4 CMOS RAM. No thermal neutron induced upsets are believed to have occurred. GeV protons, simulating primary cosmic rays, caused upsets at levels of 107 particles/cm2-upset.     

闪烁体／光纤量能器的结构,材料和抗辐照能力

描述了闪烁体／光纤的不同结构和材料对量能器抗辐照能力的影响。用北京正负电子对撞机将～１ＧｅＶ电子束对五个量能器模型逐步辐照到１０ｋＧｙ或６０ｋＧｙ。通过对不同累积辐照剂量时各模型不同断面的光产额的测量，研究和比较了辐照引起的损伤及损伤后的恢复。     

Accurate universal parameterization of absorption cross sections II--neutron absorption cross sections

A recent parameterization (here after referred as paper I, Ref. [4]) of absorption cross sections for any system of charged ions collisions including proton -nucleus collisions, is extended for neutron-nucleus collisions valid from approximately 1 MeV to a few GeV, thus providing a comprehensive picture of absorption cross sections for any system of collision pair (charged and/or uncharged). The parameters are associated with the physics of the problem. At lower energies, the optical potential at the surface is important and the Pauli operator plays an increasingly important role at intermediate energies. The agreement between the calculated and experimental data is better than earlier published results.     

A new TOF system for target recoil-ion momentum spectroscopy at IMP

A high resolution time measurement system with high data transfer rate was designed for the COLTRIMS (Cold Target Recoil-Ion Momentum Spectroscopy) system in Institute of Modern Physics,Chinese Academy of Sciences.It is used to measure the Time of Flight(TOF) with a high resolution for all 20 channels.Based on the PCI Extensions for Instrumentation(PXI) standard,the readout electronics system consists of one Clock-Trigger fan-out module and four TOF modules.Test results show that the system meets the demands of COLTRIMS,with a time resolution of better than 25 ps and a data transfer rate over 20 MB/s.     

Patterned microstructures formed with MeV Au implantation in Si(1 0 0)

Energetic (MeV) Au implantation in Si(1 0 0) (n-type) through masked micropatterns has been used to create layers resistant to KOH wet etching. Microscale patterns were produced in PMMA and SU(8) resist coatings on the silicon substrates using P-beam writing and developed. The silicon substrates were subsequently exposed using 1.5 MeV Au³⁺ ions with fluences as high as 1 × 10¹⁶ ions/cm² and additional patterns were exposed using copper scanning electron microscope calibration grids as masks on the silicon substrates. When wet etched with KOH microstructures were created in the silicon due to the resistance to KOH etching cause by the Au implantation. The process of combining the fabrication of masked patterns with P-beam writing with broad beam Au implantation through the masks can be a promising, cost-effective process for nanostructure engineering with Si.