Pulse-shape discrimination between electron and nuclear recoils in a NaI(Tl) crystal
H. S. Lee, G. Adhikari, P. Adhikari, S. Choi, I. S. Hahn, E. J. Jeon, H. W. Joo, W. G. Kang, G. B. Kim, H. J. Kim, H. O. Kim, K. W. Kim, N. Y. Kim, S. K. Kim, Y… 展开作者
H. S. Lee, G. Adhikari, P. Adhikari, S. Choi, I. S. Hahn, E. J. Jeon, H. W. Joo, W. G. Kang, G. B. Kim, H. J. Kim, H. O. Kim, K. W. Kim, N. Y. Kim, S. K. Kim, Y. D. Kim, Y. H. Kim, J. H. Lee, M. H. Lee, D. S. Leonard, J. Li, S. Y. Oh, S. L. Olsen, H. K. Park, H. S. Park, K. S. Park, J. H. Shim, J. H. So
本文报道了高光输出NaI（Tl）晶体对Am-Be源中子引起的核反冲的响应，并与对$^{137}$ Cs源康普顿散射662 keV $γ$ -射线产生的电子反冲的响应进行了比较。由于NaI（Tl）探测器的高光输出，NaI（Tl）晶体的脉冲形状鉴别（PSD）功率得到了显著提高。用品质因数量化PSD功率，估计了大质量弱相互作用粒子（WIMPs）与核子相互作用率的灵敏度，并与DAMA/LIBRA实验观测到的年调制幅度进行了比较.利用标准晕模型，利用模拟实验，估算了基于100 kg $\cdot$年的NaI探测器数据的自旋无关WIMP-核子相互作用灵敏度.
英文摘要：
We report on the response of a high light-output NaI(Tl) crystal to nuclear recoils induced by neutrons from an Am-Be source and compare the results with the response to electron recoils produced by Compton scattered 662 keV $γ$-rays from a $^{137}$Cs source. The measured pulse-shape discrimination (PSD) power of the NaI(Tl) crystal is found to be significantly improved because of the high light output of the NaI(Tl) detector. We quantify the PSD power with a quality factor and estimate the sensitivity to the interaction rate for weakly interacting massive particles (WIMPs) with nucleons, and the result is compared with the annual modulation amplitude observed by the DAMA/LIBRA experiment. The sensitivity to spin-independent WIMP-nucleon interactions based on 100 kg$\cdot$year of data from NaI detectors is estimated with simulated experiments, using the standard halo model.
MIMAC low energy electron-recoil discrimination measured with fast neutrons
MIMAC（MIcro-TPC MATERIAL of Chambers）是一个定向WIMP暗物质探测器项目。直接的暗物质实验需要高水平的电子/反冲鉴别来寻找由WIMP-核弹性散射产生的核反冲。在本文中，我们提出了一个原始的方法，电子事件拒绝的基础上，应用于实验数据采集单色中子场的多元分析。该分析表明，$10^5$抑制功率对于电子/反冲辨别是可达到的。此外，通过蒙特卡罗模拟估计效率，表明在考虑全能量范围的情况下，利用$86.49\pm 0.17$ \%的核反冲效率达到105电子排斥功率，并且在考虑5 keV的低阈值的情况下，利用$94.67\pm0.19$ \%的核反冲效率达到105电子排斥功率。
The ArDM experiment completed a single-phase commissioning run in 2015 with an active liquid argon target of nearly one tonne in mass. The analysis of the data and comparison to simulations allowed for a test of the crucial detector properties and confirmed the low background performance of the setup. The statistical rejection power for electron recoil events using the pulse shape discrimination method was estimated using data from a Cf-252 neutron calibration source. Electron and nuclear recoil band profiles were found to be well described by Gaussian distributions. Employing such a model we …
Low-Mass WIMP Sensitivity and Statistical Discrimination of Electron and Nuclear Recoils by Varying Luke-Neganov Phonon Gain in Semiconductor Detectors
在半导体暗物质探测器中放大声子信号可以通过在高电压偏置下操作并将静电势能转换成Luke-Neganov声子来实现。这种放大方法已经在高达|E| = 40 V/cm的电压下得到验证，在CDMS II Ge探测器中不会产生泄漏，允许对质量= 8 GeV和截面为1.8 e-42 cm ^2的基准WIMP的灵敏度，假设在阈值附近的电子反冲背景是平坦的。此外，我们第一次表明，核和电子反冲的Luke-Neganov增益的差异可以用来区分低能量背景和假设的WIMP信号之间的统计操作在两个不同的电压偏置。具体来说，对于一个模拟的20千克-天的实验，99%的事件的p值<1 e-8，其中基准WIMP信号的质量= 8 GeV，截面= 3.3 e-41 cm ^2。
It has been known that decays of daughter elements of $^{222}$Rn on the surface of a detector cause significant background at energies below 10 keV. In particular $^{210}$Pb and $^{210}$Po decays on the crystal surface result in significant background for dark matter search experiments with NaI(Tl) crystals. In this report, measurement of $^{210}$Pb and $^{210}$Po decays on surfaces are obtained by using a $^{222}$Rn contaminated crystal. Alpha decay events of $^{210}$Po on the surface are measured by coincidence requirements of two attached crystals. Due to recoiling of $^{206}$Pb, rapid nucl…
We report on the response of liquid xenon to low energy electronic recoils below 15 keV from beta decays of tritium at drift fields of 92 V/cm, 154 V/cm and 366 V/cm using the XENON100 detector. A data-to-simulation fitting method based on Markov Chain Monte Carlo is used to extract the photon yields and recombination fluctuations from the experimental data. The photon yields measured at the two lower fields are in agreement with those from literature; additional measurements at a higher field of 366 V/cm are presented. The electronic and nuclear recoil discrimination as well as its dependence…
Bulk NaI(Tl) scintillation low energy events selection with the ANAIS-0 module
从一些目标核散射的暗物质粒子预计以核反冲的形式沉积非常小的能量（低于100 keV）。由于核反冲与电子反冲的闪烁效率低，在寻找暗物质时考虑的大多数闪烁目标中，低于10 keVee的区域集中了大部分预期的暗物质信号。为此，需要非常低的能量阈值（等于或低于2keVee）和非常低的背景。ANAIS（Annual Modulation with NaI Scintillators）实验。对真实闪烁事件的探测器响应函数的良好了解，对在该能量范围内起作用的其他异常或噪声事件群体的良好表征，以及对后者的方便的滤波程序的开发是强制性的，以在如此低的能量下实现所需的低背景。在这项工作中，我们将提出具体的协议，选择散装闪烁事件在碘化钠（铊），其应用程序获得的数据与ANAIS-0原型。预期在NaI（Tl）中由核或电子反冲产生的闪烁脉冲中的时间常数略有差异，因此为了分析这些过滤程序在可归因于暗物质的反冲群体的情况下的效果，使用了中子校准的数据。
Superfluid $^4$He is a promising target material for direct detection of light ($<$ 1 GeV) dark matter. Possible signal channels available for readout in this medium include prompt photons, triplet excimers, and roton and phonon quasiparticles. The relative yield of these signals has implications for the sensitivity and discrimination power of a superfluid $^4$He dark matter detector. Using a 16~cm$^3$ volume of 1.75~K superfluid $^4$He read out by six immersed photomultiplier tubes, we measured the scintillation from electronic recoils ranging between 36.3 and 185 keV$_\mathrm{ee}$, yielding …
Testing the DAMA/LIBRA annual modulation result independently of dark matter particle and halo models has been a challenge for twenty years. Using the same target material, NaI(Tl), is required and presently two experiments, ANAIS-112 and COSINE-100, are running for such a goal. A precise knowledge of the detector response to nuclear recoils is mandatory because this is the most likely channel to find the dark matter signal. The light produced by nuclear recoils is quenched with respect to that produced by electrons by a factor that has to be measured experimentally. However, current quenching…
A technique using layered wavelength shifting, scintillating and non-scintillating films is presented to achieve discrimination of surface $α$ events from low-energy nuclear recoils in liquid argon detectors. A discrimination power greater than $10^{8}$, similar to the discrimination possible for electronic recoils in argon, can be achieved by adding a 50 micron layer of scintillator with a suitably slow decay time, approximately 300 ns or greater, to a wavelength-shifter coated surface. The technique would allow suppression of surface $α$ events in a very large next-generation argon dark matt…
Scintillating NaI(Tl) crystals are used for various rare decay experiments, such as dark matter searches. The hygroscopicity of NaI(Tl) crystal makes the construction of crystal detectors in these experiments challenging and requires a tight encapsulation to prevent from air contact. More importantly, in a low radioactivity measurement, identification of external radiations and surface contamination is crucial to characterize the origin of total crystal radioactivities. Studies for NaI(Tl) crystal encapsulation with active organic scintillator vetoes have been performed to mitigate the above-m…
Analysis of the 40K contamination in NaI(Tl) crystals from different providers in the frame of the ANAIS project
利用NaI（Tl）大晶体在探测器中的闪烁信号，通过探测器中目标核的弹性散射，寻找银河系中的暗物质粒子。然而，以核反冲形式沉积的能量很小，这增加了将该能量转换成闪烁的低效率，使得处于或非常接近能量阈值的事件，归因于放射性背景或伪噪声（非本体NaI（Tl）闪烁事件），可以损害这样的实验的灵敏度目标。DAMA/LIBRA实验，使用250公斤碘化钠（铊）目标，报告了第一个证据的存在，每年调制的检测率与预期的暗物质信号在6 keVee（电子当量能量）以下的区域兼容。在ANAIS（Annual modulation with NaI Scintillators）暗物质搜寻计划的框架内，为了理解大型碘化钠探测器中极低能量事件的起源，并开发方便的滤波器以滤除那些与大块NaI（Tl）晶体中的闪烁无关的事件，进行了大量而长期的努力。40 K可能是NaI（Tl）探测器中最相关的放射性污染物，因为它在非常低的能量下对本底有重要的贡献。ANAIS的目标是达到或低于20 ppb的天然钾水平。在本文中，我们将报告我们的努力，以确定40 K污染的几个NaI（Tl）晶体之间的符合测量，其中两个（或更多）。本文将比较不同供应商的晶体40 K含量的结果，并简要回顾ANAIS暗物质搜索实验的前景。
We propose a new method for the discrimination of sub-micron nuclear recoil tracks from an instrumental background in fine-grain nuclear emulsions used in the directional dark matter search. The proposed method uses a 3D Convolutional Neural Network, whose parameters are optimised by Bayesian search. Unlike previous studies focused on extracting the directional information, we focus on the signal/background separation exploiting the polarisation dependence of the Localised Surface Plasmon Resonance phenomenon. Comparing the proposed method with the conventional cut-based approach shows a signi…
