Design studies of the PWO Forward End-cap calorimeter for P̄ANDA

The P?ANDA detection system at FAIR, Germany, is designed to study antiproton-proton annihilations, in order to investigate, among others, the realm of charm-meson states and glueballs, which has still much to reveal. The yet unknown properties of this field are to be unraveled through studying QCD phenomena in the non-perturbative regime. The multipurpose P?ANDA detector will be capable of tracking, calorimetry, and particle identification, and is planned to run at high luminosities providing average reaction rates up to 2 · 10⁷ interactions/s. The envisaged physics program requires measurements of photons and charged particles with excellent energy, position, and time resolutions. The electromagnetic calorimeter (EMC) will serve as one of the basic components of the detector setup and comprises cooled lead-tungstate (PbWO₄) crystals. This paper presents the mechanical design of the Forward End-cap calorimeter and analyzes the response of the Forward End-cap calorimeter in conjunction with the full EMC and the complete P?ANDA detector. The simulation studies are focused on the performance of the planned EMC with respect to the energy and spatial resolution of the reconstructed photons. Results of the Monte Carlo simulations, excluding very low-energy photons, have been validated by data obtained from a prototype calorimeter and shown to fulfil the requirements imposed by the P?ANDA physics program.     

The Forward Vertex upgrade detector for PHENIX

The PHENIX detector at RHIC has been built with a strong heavy quark particles identification capability. These unique probes of matter are essential to adequately understand in-medium energy loss and to test the basic properties of QCD. The current PHENIX heavy flavor physics program will be significantly enhanced by the addition of the Forward Silicon Vertex upgrade detector (FVTX) in the acceptance of the existing muon arm detectors (1.2<|y|<2.4). The proposed tracker is planned to be put into operation in FY2011. Each arm of the FVTX detector consists of 4 disks of silicon strip sensors combined with FPHX readout chips and provides a precision measurement of the radial coordinate of the track. The current status of the detector design and construction and expectations for the physics signal extraction will be presented.     

Measurement of H→μ~+μ~- production in association with a Z boson at the CEPC

The Circular Electron-Positron Collider(CEPC) is a future Higgs factory proposed by the Chinese high energy physics community. It is planned to operate at a center-of-mass energy of 240–250 Ge V and is expected to accumulate an integrated luminosity of 5 ab~(-1) over ten years of operation. At the CEPC, Higgs bosons will be dominantly produced from the ZH associated process. The vast number of Higgs events collected will enable precise studies of its properties, including Yukawa couplings to massive particles. With GEANT4-based simulation of detector effects, we study the feasibility of measuring the Higgs boson decaying into a pair of muons at the CEPC.The results with and without information from the Z boson decay products are provided, showing that a signal significance of over 10 standard deviations can be achieved and the H-μ-μ coupling can be measured within 10%accuracy.     

The microcalorimeter X-ray detector: A true paradigm shift in X-ray spectroscopy

The microcalorimeter x-ray detector registers the heat deposited in an absorber from individual x-ray photons by means of a sensitive thermometer. It combines advantages of wavelength-dispersive and energy-dispersive detectors: relatively high energy resolution over a broad energy spectrum. Operating at very low temperatures reduces the noise, making the high energy resolution possible. The absorber can be tailored to any energy range, from soft x-rays to gamma rays. After many years of development, several designs have reached a level of performance and reliability that makes them competitive x-ray detectors for many kinds of experiment. We survey current microcalorimeter detectors using several different thermometers. Their applications already run from chemical analysis to plasma physics and x-ray astronomy. We describe two examples of how the microcalorimeter detector can enable novel determinations in x-ray physics.     

India-based Neutrino Observatory (INO)

We present some physics possibilities with an iron calorimeter detector (ICAL) and a status report on the feasibility study to construct such a detector at a future possible India-based Neutrino Observatory (INO). This talk was given at the workshop on high energy physics phenomenology, WHEPP-8, in Jan. 2004, at IIT Bombay.     

在线测量低能离子束电荷态和能量的新型探测器

基于加速器装置的离子与物质相互作用过程研究,在原子物理、材料、生物等诸多领域具有重要的科学意义和应用价值。本工作设计并研发了一种新型磁谱仪离子探测器,主要由高稳定性偏转磁铁、大面积位置灵敏探测器、空间匹配的散射腔室构成,可以准确在线测量不同离子的电荷态分布以及对应的能谱信息。基于HIRFL加速器装置,完成了该探测器装置的在线标定工作,获得了探测器位置信号与离子能谱之间的定量关系,给出了定标实验条件下该探测系统的最佳能谱精度和能量分辨率分别为0.1%及0.8%。     

The future of hard and electromagnetic probes at RHIC

Potential near- and long-term physics opportunities with jets, heavy flavors and electromagnetic probes at RHIC are presented. Much new physics remains to be unveiled using these probes, due to their sensitivity to the initial high density stage of RHIC collisions, when quark-gluon plasma (QGP) formation is expected. Additional physics will include addressing deconfinement, chiral symmetry restoration, properties of the strongly-coupled QGP and a possible weakly-interacting QGP, color glass condensate in the initial state, and hadronization. To fully realize the physics prospects of the RHIC energy regime, new detector components must be added to existing experiments, the RHIC machine luminosity upgraded, and a possible new detector with significantly extended coverage and capabilities added.Arrival of the final proofs: 26 July 2005PACS: 25.75Nq     

Hadronization and chirality in strongly interacting partonic matter — The future of the RHIC Program

New physics and detector concepts for a future pp and heavy ion program at the RHIC-II accelerator facility will be discussed. I will focus on hadronic observables which enable us to gain a better understanding on the hadronization from a sQGP and the chiral symmetry restoration in a sQGP. The ultimate question of how matter acquires mass can be addressed by this program in a complementary way to the Higgs search in high energy physics. The contributions of the RHIC program to the study of QCD will be discussed in detail.     

揭开中微子和反中微子的马约拉纳神秘面纱——无中微子双贝塔衰变低温晶体量热器实验

中微子可能的马约拉纳粒子属性超出了目前标准模型的范畴,是粒子物理与核物理研究领域最重要的科学问题之一.无中微子双贝塔衰变(0vββ)实验是能够确定中微子马约拉纳属性的唯一途径.0vββ的发现可以揭示中微子绝对质量、轻子数破缺、物质一反物质不对称等一系列自然奥秘,是当今粒子物理与核物理研究的前沿课题.在探索无中微子双贝塔...     

Simulation study using GEANT4 Monte Carlo code for a Gd-coated resistive plate chamber as a thermal neutron detector

The Resistive Plate Chamber (RPC) has been developed in many application areas ever since its introduction, from high energy physics experiments to positron emission tomography. Such detectors can be coated with a Gd layer that enables them to detect thermal neutrons. Consequently these RPCs can be utilized for industrial and medical purposes. Here, we present the configuration of a resistive plate chamber which is utilized to detect thermal neutrons by employing GEANT4 Monte Carlo code. The response of the RPC was evaluated as a function of neutron energy in the GEANT4 Monte Carlo code. The simulation results are taken for incident neutron energy in the energy range from 25 meV to 100 meV. The detection efficiency was found to be between 10% and 20%, depending on the detector configuration, for incident thermal neutrons of 25 meV energy.     

Study of beamstrahlung effects at CEPC

The discovery of a 125 GeV Higgs boson at the LHC marked a breakthrough in particle physics. The relative lightness of the new particle has inspired consideration of a high-luminosity Circular Electron Positron Collider(CEPC) as a Higgs Factory to study the particle's properties in an extremely clean environment. Given the high luminosity and high energy of the CEPC, beamstrahlung is one of the most important sources of beaminduced background that might degrade the detector performance. It can introduce even more background to the detector through the consequent electron-positron pair production and hadronic event generation. In this paper,beamstrahlung-induced backgrounds are estimated with both analytical methods and Monte Carlo simulation. Hit density due to detector backgrounds at the first vertex detector layer is found to be~0.2 hits/cm~2 per bunch crossing, resulting in a low detector occupancy below 0.5%. Non-ionizing energy loss(NIEL) and total ionizing dose(TID), representing the radiation damage effects, are estimated to be~10~(11)1 Me V neq/cm~2/yr and~300 k Rad/yr,respectively.     

基于Geant4的反应堆临界及动态计算方法

Geant4是一款基于C++面向对象技术的蒙特卡罗开发程序包,可以模拟各种已知粒子与物质之间的相互作用。然而该程序包没有提供临界源功能,无法直接用于反应堆物理计算。因此,利用Geant4提供的基础物理模型和粒子跟踪控制等功能,用两种不同方法实现了临界源的设置,实现了基于Geant4的反应堆静态计算程序G4-RSM和反应堆动态计算程序G4-RDM。两个程序均可用于反应堆临界计算,与MCNP计算结果相对误差在5%以内。G4-RDM程序除可用于临界计算外,还可用于模拟堆内事故工况下的中子学瞬态变化。     

粒子探测器的进展

本文简要地评述粒子探测器的发展近况。文中讨论了以下问题:大型高能粒子探测器、高能实验电子学及探测器物理。     

Collider physics at high energies and low luminosities

While very high acceleration gradients are expected in novel accelerating schemes such as those discussed by IZEST, generating high luminosities will be extremely challenging and will likely require a separate technology revolution. It is important to determine if a low-luminosity but high energy collider would have serious interest from a particle physics perspective. We consider a process involving physics beyond the Standard Model that would be detectable at high energies without requiring the types of luminosities normally quoted for future colliders, “classicalization”. In this example, scattering cross sections grow with a power of the center-of-mass energy, thereby reducing the luminosity requirement at high energies. Another process discussed is deep-inelastic-scattering of electrons on protons, where a precision measurement of the energy dependence of the scattering cross section could yield information about physics processes at much higher scales.     

基于4H-SiC的高能量分辨率α粒子探测器

为突破传统半导体核探测器耐高温与抗辐照性能不足的瓶颈,采用4H-SiC宽禁带半导体材料研制了4H-SiC探测器,并研究其构成的探测系统对α粒子的能量分辨率和能量线性度。所研制4H-SiC探测器漏电流低,当外加反向偏压为200V时,其漏电流仅14.92nA/cm2。采用具有5种主要能量α粒子的226 Ra源研究其构成的探测系统对α粒子的能量分辨率,获得4H-SiC探测系统对4.8~7.7 MeV能量范围内α粒子的能量分辨率为0.61%~0.90%,与国际上报道的高分辨4H-SiC探测系统能量分辨率一致。同时,实验结果表明:4H-SiC探测系统对该能量范围内α粒子的能量线性度十分优异,线性相关系数为0.999 99。     

Physics program of open charm and heavy c(c-) states at the BES-Ⅲ experiment

We present the physics program of the open charm and heavy c(c-)states above the D(D-)production energy threshold,which will be studied with the BES-Ⅲ detector at the BEPC-Ⅱ collider in the coming years.Based on some full Monte Carlo simulations with the BES-Ⅲ detector,we predict the accuracy levels on measuring some physical quantities related to D0,D+and D+s decays as well as some non-charmed decays of the heavy c(c-)states.     

电子照相技术成像模拟研究

针对高能电子照相的关键物理过程开展蒙特卡罗照相模拟研究,采用Geant4围绕2.5 GeV电子在四极透镜组内的输运、电子与物质相互作用衰减等照相基本过程展开研究。通过设计不同材料、不同厚度的含缺陷平板作为模拟照相客体,开展放大型电子照相系统缺陷分辨能力模拟。此外,采用不同材料、不同厚度的台阶样品,模拟获得了电子束流穿过相应面密度材料后的线扩展函数,进一步评估电子照相对实心客体的探测分辨能力。     

SNO and the new SNOLAB

A new international science laboratory, SNOLAB, has recently begun operation 2 km underground at the site of the Sudbury Neutrino Observatory (SNO), near Sudbury, Canada. The laboratory incorporates the SNO detector and includes several new experimental areas with a total excavated volume about three times larger than the original SNO cavity. The SNO detector has now completed operation with heavy water and data analysis is being completed with improved accuracy by combining all three phases of the project. A new project, SNO +, has recently been funded and will provide high sensitivity for neutrino-less double beta decay, low energy solar neutrinos, geoneutrinos, supernovae and other physics measurements. A number of dark matter measurements are in progress or preparing for deployment and a new supernova measurement, HALO is also being deployed. The status and physics objectives of the experimental program is outlined.     

锂玻璃探测器中子探测效率的刻度

为了精确测量keV能区的中子俘获截面,中国原子能科学研究院正在建造一台4π 全吸收型γ 探测装置---GTAF,锂玻璃探测器将会作为中子束流监视器测量中子能谱。利用5SDH-2 加速器刻度了锂玻璃探测器在两个入射中子单能点(250 和565 keV) 的探测效率,并使用EANT4 和MCNP 程序模拟计算了锂玻璃探测器的相对探测效率。通过归一化实验数据和模拟结果,得到了锂玻璃探测器在10keV~1 MeV 能区的中子探测效率曲线。对于把锂玻璃探测器测量得到的飞行时间谱转化为中子束流能谱,是一项非常重要的工作,同时为探测器效率刻度提供了新方法。In order to accurately measure the neutron capture cross section in the energy range of keVMeV, 4 πgamma-ray total absorption facility (GTAF) is being constructed at China Institute of Atomic Energy (CIAE). The lithium glass detector will be used as a neutron beam monitor for GTAF. The detection efficiency of the lithium glass detector at two incident neutron energy points (250, 565 keV) was calibrated in 5SDH-2 accelerator, and the relative detection efficiency was simulated by GEANT4 and MCNP code. By the normalization of the experimental data and simulation result, the neutron detection efficiency curve of the lithium glass detector between 10 keV and 1 MeV was obtained. This work will be important to convert the Time-of-flight spectrum that be measured by Li-glass detector to the energy spectrum of neutron beam, and provide the new method for calibration of detection efficiency.     

Heavy ions with the Large Hadron Collider and the ALICE detector

The Large Hadron Collider (LHC) under construction at CERN is also planned as a heavy ion collider with lead ions colliding at an energy of 2.7+2.7 ATeV. This corresponds to collisions of matter with cosmic rays of the utmost energies observed so far promising the study of new and exciting aspects of physics. Minor improvements of the newly commissioned lead ion source at the CERN SPS are necessary in order to provide a luminosity of L=2×10²⁷ cm^?2s^?1. The detector ALICE has been chosen as the third detector for the LHC and will be dedicated to the physics of these nuclear collisions and also to the large cross section physics in p+p collisions.