从北京谱仪到未来CEPC上的高能实验

 1989年4月，北京谱仪探测器（BEijing Spectrometer，BES）忠实地记录了北京正负电子对撞机（Beijing Electron Positron Collider，BEPC）的历史性的第一个物理事例，宣告中国高能加速器物理实验的肇端。转眼之间已经整整30年。这30年，中国的经济发展实现了腾飞，同时是科学技术飞速发展的30年，尤其是基础科学取得了长足进步，一些领域已经跻身国际先进行列，一些领域与国际先进水平的差距已大大缩小。     

直接测到暗物质了吗？

正20年前DAMA/LIBRA实验组展示了暗物质测量的直接证据,但一直未被肯定。如今,一个类似的实验也不支持测到了暗物质粒子。20年前,意大利DAMA/LIBRA实验组声称直接测到了暗物质粒子,此后一直被物理学家所关注。最近西班牙地下实验组ANAIS也采用NaI(Tl)闪烁体来测量,且分析了近3年的数据。     

DAMA暗物质实验本底问题的研究

文章介绍中意合作DAMA组100kgNaI(Tl)晶体阵列实验结果,重点探讨了可能影响探测实验结果的多种因素.通过蒙特卡罗模拟计算,北京组得到了探测晶体阵列内部的放射性杂质的本底贡献,它们与本底的实验结果一致.另外,模拟计算结果表明,快中子、太阳中微子等对本底的贡献很小,这样也排除了由它们引起DAMA实验结果的可能性.     

用于CBM-TOF超级模块质量评估的SoC数据读出方法

在高压缩重子物质（Compressed Baryonic Matter,CBM）实验中,多气隙电阻板室（Multi-gap Resistive Plate Chamber,MRPC）探测器被用于构建飞行时间（Time of Flight,TOF）谱仪。根据CBM实验需求,TOF谱仪被设计成由6种不同类型的超级模块构成的探测器墙。每个模块最多包含5块MRPC探测器,能提供320路电子学通道,单个模块的数据率高达6 Gbps。为了评估CBM-TOF超级模块的性能,本文提出了一种基于TCP/IP千兆以太网技术的数据读出方法。考虑到TCP/IP协议的复杂性,该方法利用AlteraSoC FPGA从前端电子学接受数字化的时间数据,并通过千兆以太网并行地发送数据到DAQ软件。实验室测试结果表明,单个读出扣板全链路读出速率达到550 Mbps,能够用于CBM-TOF MRPC探测器质量评估。     

3.8μm激光破坏三元PC型HgCdTe探测器系统的实验研究

 对3.8μm激光破坏三元PC型HgCdTe探测器系统的实验结果进行定性分析。实验结果表明：当辐照在探测器系统上的激光功率密度达411W/cm²时，系统内各部件（Ge窗口、滤光片及探测器）已严重损坏，探测器系统永久失效。分析认为：实验中引起探测器系统破坏的主要原因是温度升高引起的烧蚀热。     

绝对辐射功率计

绝对辐射功率计周曼（南京林业大学２１００３７）现有的光探测器大致分成两类，利用光辐射热效应的热敏探测器和基于光电效应的光电探测器．本文介绍利用热敏探测器的物理思想制做的绝对辐射功率计，用以测量黑体炉、红外灯等辐射源的辐射功率，以加深对辐射体的认识．一...     

液氩探测器在稀有事例探测中的应用和发展

稀有事例探测是近几年热门的粒子物理前沿课题,如暗物质、无中微子双贝塔衰变、中微子-核子相干弹性散射等实验都在逐渐被规划和实施.进行稀有事例探测要求探测器有极佳的性能,同时对环境本底有很高的要求,因此探测器和相关材料的选择是稀有事例探测的一个重要课题.液氩因为成本低、闪烁性能好、体积限制较小等优势成为稀有事例探测器的一种重要介质.经过几十年的发展,单相液氩闪烁体探测器和两相氩时间投影室成为两种常见的液氩探测器类型,并开始被国内外各实验组应用于稀有事例探测实验中.本文首先对两种常见的液氩探测器的原理和特性进行介绍,然后详细介绍国内外相关稀有事例探测实验组对液氩探测器的研究和应用现状以及未来规划,最后讨论未来液氩探测器在稀有事例探测中的应用前景和优化方向.     

利用快响应金刚石（Ⅱa型）光导探测器测量X射线

文中介绍了金刚石光导探测器的工作原理呼简化模型以及这种探测器所具有的独特的优点，并在激光－金（Ａｕ）平面靶实验中用来测量Ｘ射线，根据文献中灵敏度标定值给出激发辐照Ａｕ平面靶Ｘ光转换率为２７％左右，与目前公认的结果相一致。     

“多普勒效应”实验的教学内容及仪器配备的优化探讨

“多普勒效应”实验的教学内容及仪器配备的优化探讨陆雨时，叶善专，孙晓玲（东南大学物理系南京２１００１８）前去多普勒效应随着科学技术的发展，已成为近０工程、军事、天文和生物等领域中常用的基础理评之一．国家教委工科物理课程指导委员会实验组，将“多普勒效应...     

DAMPE-PSD探测单元模块大动态范围读出方案的实验验证

暗物质粒子探测卫星（Dark Matter Particle Explorer,DAMPE）的塑闪阵列探测器（Plastic Scintillator Detector,PSD）需要实现高能e/γ粒子的鉴别功能以及对Z=1~20的宇宙线重离子的电荷测量功能。它使用光电倍增管作为读出器件,并从打拿极5和打拿极8同时引出信号来增大读出动态范围。基于该设计方案的探测单元模块在兰州重离子加速器冷却储存环（HIRFL-CSR）上的外靶终端（ETF）进行了束流测试实验。实验得到了PSD单元条在中能轻核区（Z≤8）的能量响应,并证明了单元条的衰减长度与入射粒子种类无关。通过将实验结果外推至高能重核区,同时结合衰减长度、入射角度和能量涨落等因素,可以估算出PSD探测单元模块输出信号幅度的动态范围。结果显示,该范围在PSD前端电子学模块的线性工作区间内,从而验证了PSD大动态范围读出方案设计的合理性。The Plastic Scintillator Detector (PSD) of DArk Matter Particle Explorer (DAMPE) aims for high energy e/γ identification and charge measurement for cosmic-ray ions from Z=1~20. It adopts photomultiplier tube as the readout device and extracts signals from both dynode5 and dynode8 to enlarge the readout dynamic range. A beam test on a PSD detector unit based this design has been carried out at the External Target Facility (ETF) terminal of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou (HIRFL-CSR). The detector response to light nuclei (Z≤8) at the medium energy scale was extracted and the attenuation length was proved to be irrelevant with the impinging nuclei species. By extrapolating the result to heavy nuclei at the high energy scale and taking into account light attenuation, energy fluctuation and imping angle, the dynamic range of the output signal of PSD detector unit was estimated. The range is well within the linear range of the front-end electronics of PSD, thus verifies the large dynamic range readout design of PSD.     

Results from a low-energy analysis of the CDMS II germanium data

We report results from a reanalysis of data from the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory. Data taken between October 2006 and September 2008 using eight germanium detectors are reanalyzed with a lowered, 2 keV recoil-energy threshold, to give increased sensitivity to interactions from weakly interacting massive particles (WIMPs) with masses below ～10 GeV/c(2). This analysis provides stronger constraints than previous CDMS II results for WIMP masses below 9 GeV/c(2) and excludes parameter space associated with possible low-mass WIMP signals from the DAMA/LIBRA and CoGeNT experiments.     

Exclusion limits on the WIMP-nucleon cross section from the cryogenic dark matter search

The Cryogenic Dark Matter Search (CDMS) employs Ge and Si detectors to search for weakly interacting massive particles (WIMPs) via their elastic-scattering interactions with nuclei while discriminating against interactions of background particles. CDMS data, accounting for the neutron background, give limits on the spin-independent WIMP-nucleon elastic-scattering cross section that exclude unexplored parameter space above 10 GeV/c2 WIMP mass and, at >75% C.L., the entire 3sigma allowed region for the WIMP signal reported by the DAMA experiment.     

Results from DAMA/LIBRA at Gran Sasso

The DAMA project is an observatory for rare processes and it is operative deep underground at the Gran Sasso National Laboratory of the I.N.F.N. In particular, the DAMA/LIBRA (Large sodium Iodide Bulk for RAre processes) set-up consists of highly radiopure NaI(Tl) detectors for a total sensitive exposed mass of ?250 kg. Recent results, obtained by this set-up by exploiting the model independent annual modulation signature of Dark Matter (DM) particles, have confirmed and improved those obtained by the former DAMA/NaI experiment. A model independent evidence for the presence of Dark Matter particles in the galactic halo is cumulatively obtained at 8.2?σ C.L. No systematics or side reactions able to account for the measured modulation amplitude and to contemporaneously satisfy all the many specific requirements of the signature have been found or suggested by anyone over more than a decade. An example of one of the many possible model dependent corollary quests for the candidate particles and for the related astrophysical, nuclear and particle physics scenarios is presented considering the whole cumulative exposure. Future perspectives are shortly addressed.     

Particle dark matter in the galactic halo

The presence of Dark Matter (DM) particles in the galactic halo can be unambiguously pointed out in a model-independent way by exploiting the DM annual modulation signature with an apparatus of specific features placed deep underground. At present DAMA/LIBRA is running at the Gran Sasso National Laboratory of the I.N.F.N. and has presented so far the results obtained with the data collected in the first six annual cycles (exposure 0.87 ton × yr). When including the exposure of the former DAMA/NaI experiment (0.29 ton × yr), the total exposure is 1.17 ton × yr for 13 annual cycles, a value order of magnitude larger than those typically released in the field. These DAMA/LIBRA data have further confirmed the model-independent evidence of the presence of Dark Matter particles in the galactic halo on the basis of the exploited DM signature (8.9 σ C.L. for the cumulative exposure).     

New results from DAMA/LIBRA

DAMA/LIBRA is running at the Gran Sasso National Laboratory of the I.N.F.N. Here the results obtained with a further exposure of 0.34 ton × yr are presented. They refer to two further annual cycles collected one before and one after the first DAMA/LIBRA upgrade occurred on September/October 2008. The cumulative exposure with those previously released by the former DAMA/NaI and by DAMA/LIBRA is now 1.17 ton × yr, corresponding to 13 annual cycles. The data further confirm the previous positive results obtained investigating the presence of Dark Matter (DM) particles in the galactic halo by means of the model independent Dark Matter annual modulation signature; the confidence level is now 8.9 σ for the cumulative exposure. In particular, with the cumulative exposure the modulation amplitude of the single-hit events in the (2–6) keV energy interval measured in NaI(Tl) target is (0.0116±0.0013) cpd/kg/keV; the measured phase is (146±7) days and the measured period is (0.999±0.002) yr, values well in agreement with those expected for the DM particles.     

Direct dark matter investigation

Experimental efforts and theoretical developments support that most of the Universe is dark and a large fraction of it should be made of relic particles; many possibilities are open on their nature and interaction types. This motivates experimental efforts to investigate the direct detection of these particles with various techniques. In particular, experiments offering a model independent signature for the presence of Dark Matter (DM) particles in the Galactic halo are mandatory. In this paper some general arguments will be summarized and particular care will be given to the results obtained by the DAMA/LIBRA experiment (sensitive mass: ～250 kg) at the Gran Sasso National Laboratory of the I.N.F.N. by exploiting the model independent DM annual modulation signature with higly radiopure NaI(Tl) target-detectors. Cumulatively with the former DAMA/NaI (sensitive mass: ～100 kg) an exposure of 1.17 ton yr, collected over 13 annual cycles, has been released so far; a model independent evidence of the presence of DM particles in the galactic halo is supported at 8.9 ρ confidence level (C.L.). In addition, experimental and theoretical uncertainties and their implications in the interpretation and comparison of different kinds of results will be shortly addressed. Some perspectives will be mentioned.     

First results from DAMA/LIBRA and the combined results with DAMA/NaI

The highly radiopure ≃ 250 kg NaI(Tl) DAMA/LIBRA set-up is running at the Gran Sasso National Laboratory of the INFN. In this paper the first result obtained by exploiting the model independent annual modulation signature for Dark Matter (DM) particles is presented. It refers to an exposure of 0.53 ton×yr. The collected DAMA/LIBRA data satisfy all the many peculiarities of the DM annual modulation signature. Neither systematic effects nor side reactions able to account for the observed modulation amplitude and to contemporaneously satisfy all the several requirements of this DM signature are available. Considering the former DAMA/NaI and the present DAMA/LIBRA data all together (total exposure 0.82 ton×yr), the presence of Dark Matter particles in the galactic halo is supported, on the basis of the DM annual modulation signature, at 8.2 σ C.L.; in particular, in the energy interval (2–6) keV, the modulation amplitude is (0.0131±0.0016) cpd/kg/keV and the phase and the period are well compatible with June 2 ^nd and one year, respectively.     

The impossibility of heavy neutrino dark matter in the Littlest Higgs Model with T-parity: Constraints from direct search

We consider the Littlest Higgs Model with T-parity (LHT), in the parameter region where a heavy neutrino is the lightest T-odd particle (LTP). Having emphasized that this corresponds to a sizable region in the parameter space of the theory, we show that both the Cryogenic Dark Matter Search (CDMS) and Xenon10 experiments disallow the entire region where the masses of the new particles in LHT can lie within several TeV. Therefore, any observation of the signals of a heavy neutrino LTP is likely to seriously reopen the issue of cold dark matter in the universe.     

Review of dark matter direct detection experiments

Matter, as we know it, makes up less than 5% of the Universe. Various astrophysical observations have confirmed that one quarter of the Universe and most of the matter content in the Universe is made up of dark matter. The nature of dark matter is yet to be discovered and is one of the biggest questions in physics. Particle physics combined with astrophysical measurements of the abundance gives rise to a dark matter candidate called weakly interacting massive particle (WIMP). The low density of WIMPs in the galaxies and the extremely weak nature of the interaction with ordinary matter make detection of the WIMP an extraordinarily challenging task, with abundant fakes from various radioactive and cosmogenic backgrounds with much stronger electromagnetic interaction. The extremely weak nature of the WIMP interaction dictates detectors that have extremely low naturally occurring radioactive background, a large active volume (mass) of sensitive detector material to maximize statistics, a highly efficient detector-based rejection mechanism for the dominant electromagnetic background and sophisticated analysis techniques to reject any residual background. This paper reviews currently available major technologies being pursued by various collaborations, with special emphasis on the cryogenic Ge detector technology used by the Cryogenic Dark Matter Search Collaboration (CDMS).     

Dark matter search with the HDMS-experiment and the GENIUS project

We present a new Germanium Dark Matter Experiment. It consists of two HPGe-Detectors which are run in a unique configuration. The anticoincidence between the two detectors will further reduce the background that we achieve now in the Heidelberg-Moscow-Experiment and will allow to improve WIMP cross section limits to a level comparable to planned cryogenic experiments. This should also allow to test recently claimed positive evidence for dark matter by the DAMA experiment.We show first detector performances from the test period in the Heidelberg Low Level Laboratory and give a preliminary estimation for the background reduction efficiency. The HDMS experiment in being built up now in the Gran Sasso Underground Laboratory and will start taking data by the end of this year.For a substantial improvement of the WIMP-nucleon cross section limits, future dark matter experiments will have to be either massive direction-sensitive detectors or massive ton-scale detectors with almost zero background. A proposal for a high mass (1 ton) Ge experiment with a much further reduced background is the Heidelberg GENIUS experiment. GENIUS will be able to give a WIMP limit of the order 0.02 counts/day/kg and additionally to look for the annual modulation WIMP-signature by using raw data without subtraction.