北京谱仪桶部簇射计数器能量响应特性研究

在北京正负电子对撞机的J/ψ和Ds能区,选择了辐射巴巴事例,并以此来研究北京谱仪的桶部簇射计数器能量响应特性.在消除了由于电子和辐射光子在桶部簇射计数器中沉积能量区域重叠的影响后,正确地得到了桶部簇射计数器在电子和光子动量小于2GeV以下的能量响应,表明在所研究能区,桶部簇射计数器的能量响应线性很好.对桶部簇射计数器微小的非线性进行修正后,重建的π0不变质量谱得到改善.     

北京τ–c工厂(BTCF)快速蒙特卡罗模拟方法的开发和应用

参考国内外现有的τ-c工厂及其探测器的设计结果,给出了BTCF探测器的总体指标. 根据这些指标设计并开发了用于BTCF物理研究的快速蒙特卡罗模拟方法,并用此方法对一系列重要的物理课题进行了蒙特卡罗模拟. 文中描述了该模拟方法的设计思想、程序流程以及这种方法在BTCF可行性研究乃至预制研究阶段的优越性,同时也给出了对若干重要物理问题的模拟结果. 从而论证了建造BTCF的必要性和不可替代性.     

Simulation study of neutrino nucleus cross section measurement in a segmented detector at a spallation neutron source

Knowledge of ν_e-Fe/Pb differential cross sections for ν_e energy below several tens of MeV scale is believed to be crucial in understanding supernova physics. In a segmented detector at a spallation neutron source, ν_e energy reconstructed from the electron range measurement is strongly affected because both multiple scattering and electromagnetic showers occur along the electron passage in target materials. In order to estimate these effects, a simulation study has been performed with a cube block model assuming perfect tracking precision. The energy spectrum distortion is observed to be proportional to the atomic number of the target material. Feasibility of unfolding the distorted ν_e energy spectrum is studied for both Fe and Pb. An evaluation of the statistical accuracy attainable is therefore provided for a segmented detector.     

BES实验数据离线刻度

概述了北京谱仪(BES)各子探测器的实验离线数据刻度,包括主漂移室、飞行时间计数器、簇射计数器和μ子鉴别器.给出了BES1994年D_s运行期间的探测器运行性能,以及数据质量情况.     

北京谱仪数据的离线处理

本文介绍北京谱仪离线分析过程中数据生成的整个情况,包括事例过滤原则,重建的一般原理及物理分析(DST)数据的分类方法.通过一些典型的J/ψ衰变道的初步分析结果,展示北京谱仪已有的DST数据的首批物理信号.     

铽离子-镧系金属结合标签的荧光探针的改进

镧系金属因其具有较窄的发射光谱带,较大的斯托克斯位移以及毫秒级的荧光寿命,而被广泛应用于荧光检测中,其中Tb~(3+)、Eu~(3+)最为常用.镧系金属结合标签(Lanthanide Binding Tag,LBT)可以与蛋白质融合表达,并且一般不会影响蛋白的结构和功能,这些特点使LBT被广泛应用于蛋白质结构与功能研究中.LBT能够特异性地结合镧系金属离子,并利用LBT上色氨酸的吲哚环作为"天线"吸收外部能量,再将能量传递给镧系金属离子,进而激发镧系金属离子产生荧光.该文以经典模式蛋白泛素(Ubiquitin,Ub)作为媒介,将LBT引入到Ub的碳端,采用定点突变的方法增加LBT上吲哚环的数量,观察Ub-LBT[结合铽离子(Tb~(3+))]荧光量子产率的变化.结果表明在LBT结构中增加吲哚环的数量能够提高LBT(结合Tb~(3+))的荧光量子产率.     

Muon flux measurement at China Jinping Underground Laboratory

China Jinping Underground Laboratory(CJPL)is ideal for studying solar,geo-,and supernova neutrinos.A precise measurement of the cosmic-ray background is essential in proceeding with R&D research for these MeV-scale neutrino experiments.Using a 1-ton prototype detector for the Jinping Neutrino Experiment(JNE),we detected 264 high-energy muon events from a 645.2-day dataset from the first phase of CJPL(CJPL-I),reconstructed their directions,and measured the cosmic-ray muon flux to be (3.53±0.22_stat.±0.07_sys.)×-10^-10cm^-2.The observed angular distributions indicate the leakage of cosmic-ray muon background and agree with simulation data accounting for Jinping mountain's terrain.A survey of muon fluxes at different laboratory locations,considering both those situated under mountains and those down mine shafts,indicates that the flux at the former is generally a factor of (4±2) larger than at the latter,with the same vertical overburden.This study provides a convenient back-of-the-envelope estimation for the muon flux of an underground experiment.     

含有阈值控制策略Hindmarsh-Rose系统的簇发振荡分析

本文研究了阈值控制策略下不同尺度耦合系统的簇发振荡及其机理.以包含周期激励项的HindmarshRose模型为例,当激励频率与系统固有频率存在量级差异时,引入阈值控制策略,建立了频域间存在快慢耦合的Filippov系统.因激励项可以被视为一个慢变参数,我们可以相应地得到一个向量场不连续的广义自治系统,从而分析了系统在不同区域随慢变参数变化的平衡点及相关分岔.特别地,由于系统的非光滑特性,我们也分析了非光滑分岔出现的条件,给出了滑动区域的解析表达式.基于阈值控制策略,研究了三种切换条件下的簇发振荡,指出了非光滑分界面的变化会产生不同的非光滑分岔,进而导致不同滑动现象的发生,表现为不同形式的沉寂态与激发态.通过叠加转换相图与分岔图,簇发机理得以揭示.     

Hunting potassium geoneutrinos with liquid scintillator Cherenkov neutrino detectors

The research on geoneutrinos is a new interdisciplinary subject involving particle experiments and geo-science.Potassium-40(40K)decays contribute roughly to 1/3 of the radiogenic heat of the Earth,which is not yet accounted for by experimental observation.Solar neutrino experiments with liquid scintillators have observed uranium and thorium geoneutrinos and are the most promising experiments with regard to low-background neutrino detection.In this study,we present the new concept of using liquid-scintillator Cherenkov detectors to detect the neutrino-electron elastic scattering process of 40K geoneutrinos.Liquid-scintillator Cherenkov detectors using a slow liquid scintillator achieve this goal with both energy and direction measurements for charged particles.Given the directionality,we can significantly suppress the dominant intrinsic background originating from solar neutrinos in conventional liquid-scintillator detectors.We simulated the solar-and geo-neutrino scatterings in the slow liquid scintillator detector,and implemented energy and directional reconstructions for the recoiling electrons.We found that 40K geoneutrinos can be detected with three-standard-deviation accuracy in a kiloton-scale detector.     

发现超新星遗迹中微子——中微子天文学的下一个里程碑

超新星对于研究恒星演化以及元素、中子星、黑洞与引力波的产生至关重要。观测超新星的手段有很多种,而中微子因具有与物质相互作用极其微弱的特性,为观测提供了一个不同的视角,尤其是对超新星内部的物理机制研究。探测银河系内超新星爆发中微子,因其每世纪几次的低爆发率而变得非常困难。相比之下,距离银河系较远的周边星系超新星总爆发率每十年超过一次。正在建设的大型中微子实验已经开始能够探测宇宙大爆炸至今,包括银河系附近星系在内的所有星系中超新星爆发累积形成的各向同性中微子背景,称为超新星遗迹中微子。如果实验能发现这些中微子,将是中微子天文学的一个里程碑。文章将介绍目前和未来相关实验的主要探测原理、实验挑战和展望。