Search

Detectors with low thresholds for electron recoil open a new window to direct searches of sub-GeV dark matter (DM) candidates. In the past decade, many strong limits on DM-electron interactions have been set, but most on the one which is spin-independent (SI) of both dark matter and electron spins. In this work, we study DM-atom scattering through a spin-dependent (SD) interaction at leading order (LO), using well-benchmarked, state-of-the-art atomic many-body calculations. Exclusion limits on the SD DM-electron cross section are derived with data taken from experiments with xenon and germanium detectors at leading sensitivities. In the DM mass range of 0.1 - 10 GeV, the best limits set by the XENON1T experiment: $\sigma_e^{\textrm{(SD)}}, Comment: Data files and README are provided in the ancillary folder

This paper presents a statistical model to accurately estimate post-FEC BER for high-speed wireline links using standard linear block codes, such as the RS(544,514,15) KP4 and RS(528,514,7) KR4 codes. A hierarchical approach is adopted to analyze the propagation of PAM-symbol and FEC-symbol errors through a two-layer Markov model. A series of techniques including state aggregation, time aggregation, state reduction, and dynamic programming are introduced making the time complexity to compute post-FEC BER below 10−15 reasonable. Error bounds associated with each method are found. The efficiency of the proposed model allows it to handle a larger state space, more DFE taps, and more sophisticated linear block codes than prior work. A 4-PAM 60 Gb/s wireline transceiver fabricated in a 7 nm FinFET technology is used as a test vehicle to validate this model. Measured data with two different channels reveals that the statistical model can properly predict the post-FEC error floor with standard FEC codes. While this paper demonstrates the method for capturing DFE error propagation, the method is general and can be applied to model other communication systems having memory effects. Moreover, our proposed model can be easily extended to higher-level PAM schemes and other advanced equalizer architectures to assist in making architectural choices for wireline transceivers.

Sensor calibration is a prerequisite for autonomous driving and is vital for accurate perception, ensuring precise planning and control of the autonomous vehicle. The modern self-driving car considers data inputs from multiple sensors to construct an understanding of its surroundings. These sensors are inherently susceptible to errors arising from measurement uncertainty, and the risk is multiplied under sensor fusion, a critical function for vehicle localization and object detection. Existing works in this field of study largely focus on offline sensor calibration methods where the vehicle is assumed to have undergone the calibration process prior to vehicle operation on the road, typically using a known calibration target such as a checkerboard pattern target. This paper proposes a sensor calibration method for the LiDAR and the inertial navigation system (INS) using high definition (HD) maps as a readily available source of ground truth, giving potential to an online approach to calibration. To match the data between the LiDAR and the INS system, the trajectory from LiDAR odometry based on the normal distributions transform (NDT) and the trajectory from the INS are utilized. The HD map acts as an online calibration target and provides real positional coordinates which can correct for errors inherent to the sensor outputs and enhance the trajectory estimations. Upon the detection of miscalibration, the algorithm finds the optimum transformation matrix that aligns the LiDAR with the INS. Real-world data was used to verify the proposed approach and can be applied to find the correct extrinsic transformation matrix.

The INdia’s TIN (TIN.TIN) detector is under development in the search of neutrinoless double-β decay (0νββ) using 90% enriched 124Sn isotope as the target mass. This detector will be housed in the upcoming underground facility of the India-based Neutrino Observatory. We present the most important experimental parameters that would be used in the study of required sensitivity for the TIN.TIN experiment to probe the neutrino mass hierarchy. The sensitivity of the TIN.TIN detector in the presence of sole two neutrino double-β decay (2νββ) background is studied at various energy resolutions. The most optimistic and pessimistic scenario to probe the neutrino mass hierarchy at 3σ sensitivity level and 90% CL are discussed.

Forward-error-correction (FEC) codes have become an integral part of high-speed wireline links. Signal-to-noise ratio, minimum mean-squared error, and pre-FEC BER are common performance metrics used to design and optimize link parameters, such as the tap coefficients in feed-forward and decision-feedback equalizers. This paper shows that the equalizer parameters found by conventional methods do not necessarily minimize post-FEC BER due to the unaccounted-for negative impact of DFE error propagation on FEC performance. However, the introduction of 1/(1+D) pre-coding eliminates long error bursts so that both pre-FEC and post-FEC BER are minimized with the same equalizer coefficients. These observations may have implications on the architecture and optimization of wireline transceivers.

DSP-based transceivers above 100Gb/s have demonstrated the ability to handle up to 38dB insertion loss (IL) with low-to-moderate crosstalk –[2]. At same time, power scaling techniques [3] have closed the energy efficiency gap compared with analog/mixed-signal transceivers on shorter links. Notwithstanding advances in materials and connectors, in large repeater-less backplanes, transceivers are required to operate reliably at 100Gb/s with more than 40dB IL. Furthermore, next generation computing and AI applications require 50Gb/s rates per lane on channels with more than 45dB loss but without the latency of forward error correction (FEC). In this paper we demonstrate a reconfigurable ADC-DSP SerDes capable of operating with BER $\le 1E-05$ at 112Gb/s in PAM-4 or Duo-PAM-4 across a 45dB loss channel, and 58Gb/s PAM-2 at $\lt 1E-15$ over a 52dB loss channel without FEC, while achieving a power efficiency better than 6pJ/b. The SerDes architecture is shown in Fig. 8.4.1 and features extensive power scaling capability.

Low energy neutrinos play important role in nuclear and astrophysical processes. Such neutrinos with energy below $\sim$100 MeV are able to scatter off the nucleus via elastic scattering. Neutrino-nucleus elastic scattering ($\nu A_{el}$) provides a unique laboratory to study the quantum mechanical coherency effects in electroweak interactions. We present the detailed study and formulation of coherency effects, relate this to nuclear form factors and experimental cross-section ratios. The parameters chosen to quantify the coherency are universally applicable to different neutrino sources and target nuclei. We characterize how the energy dependence of the coherence factor leads to complementary among measurements at various neutrino sources with different targets. We also provide the constraints on coherency for the first generation discovery measurements of $\nu A_{el}$ with CsI target and theoretical expectations from Argon and Germanium target.

Scattering of light dark matter (LDM) particles with atomic electrons is studied in the context of effective field theory. Contact and long-range interactions between dark matter and an electron are both considered. A state-of-the-art many-body method is used to evaluate the spin-independent atomic ionization cross sections of LDM-electron scattering, with an estimated error about 20%. New upper limits are derived on parameter space spanned by LDM mass and effective coupling strengths using data from the CDMSlite, XENON10, XENON100, and XENON1T experiments. Comparison with existing calculations shows the importance of atomic structure. Two aspects particularly important are relativistic effect for inner-shell ionization and final-state free electron wave function which sensitively depends on the underlying atomic approaches., Comment: Update to the final publication version, largely expanded with new data analyzed and improved physics discussions. Data files and README are provided in the ancillary folder

With the rapid development of automated vehicles (AVs), more and more demands are proposed towards environmental perception. Among the commonly used sensors, MMW radar plays an important role due to its low cost, adaptability In different weather, and motion detection capability. Radar can provide different data types to satisfy requirements for various levels of autonomous driving. The objective of this study is to present an overview of the state-of-the-art radar-based technologies applied In AVs. Although several published research papers focus on MMW Radars for intelligent vehicles, no general survey on deep learning applied In radar data for autonomous vehicles exists. Therefore, we try to provide related survey In this paper. First, we introduce models and representations from millimeter-wave (MMW) radar data. Secondly, we present radar-based applications used on AVs. For low-level automated driving, radar data have been widely used In advanced driving-assistance systems (ADAS). For high-level automated driving, radar data is used In object detection, object tracking, motion prediction, and self-localization. Finally, we discuss the remaining challenges and future development direction of related studies.

We report constraints on the dark photon effective kinetic mixing parameter (${\kappa}$) with data taken from two ${p}$-type point-contact germanium detectors of the CDEX-10 experiment at the China Jinping Underground Laboratory. The 90\% confidence level upper limits on ${\kappa}$ of solar dark photon from 205.4 kg-day exposure are derived, probing new parameter space with masses (${m_V}$) from 10 to 300 eV/${c^2}$ in direct detection experiments. Considering dark photon as the cosmological dark matter, limits at 90\% confidence level with ${m_V}$ from 0.1 to 4.0 keV/${c^2}$ are set from 449.6 kg-day data, with a minimum of ${\rm{\kappa=1.3 \times 10^{-15}}}$ at ${\rm{m_V=200\ eV/c^2}}$., Comment: 5 pages, 6 figures

We present weakly interacting massive particles (WIMPs) search results performed using two approaches of effective field theory from the China Dark Matter Experiment (CDEX), based on the data from both CDEX-1B and CDEX-10 stages. In the nonrelativistic effective field theory approach, both time-integrated and annual modulation analyses were used to set new limits for the coupling of WIMP-nucleon effective operators at 90% confidence level (C.L.) and improve over the current bounds in the low $m_{\chi}$ region. In the chiral effective field theory approach, data from CDEX-10 were used to set an upper limit on WIMP-pion coupling at 90% C.L. We for the first time extended the limit to the $m_{\chi}, Comment: version accepted by Science China-PMA, 8 pages, 8 figures

Neutrino-electron scattering is a purely leptonic fundamental interaction and therefore provides an important channel to test the Standard Model (SM), especially at the low energy-momentum transfer regime [1, 2]. In this study Data on v ¯ e − e and ve − e scattering from the TEXONO and LSND experiments, respectively, are used and constraints on neutrino Non-Stardard-Interactions (NSI) couplings depending on model-independent approaches, which are described by a four-Fermi point like interaction and depending on several beyond-Standard-Model-physics scenarios, mediated by massive intermediate particles including (1) an extra Z-prime gauge boson, (2) a new light spin-1 boson (NLS1B), (3) Dark Photon (DP), and (4) a charged Higgs boson (CHB), are placed via the neutrino-electron scattering channel to test the SM at a low energy-momentum transfer regime. The relevant parameter spaces are extended by allowing light mediators.

Neutrino-nucleus elastic scattering ($\nu {\rm A}_{el}$) provides a unique laboratory to study the quantum-mechanical (QM) coherency effects in electroweak interactions. The deviations of the cross-sections from those of completely coherent systems can be quantitatively characterized through a coherency parameter $\alpha ( q^2 )$. The relations between $\alpha$ and the underlying nuclear physics in terms of nuclear form factors are derived. The dependence of cross-section on $\alpha ( q^2 )$ for the various neutrino sources is presented. The $\alpha ( q^2 )$-values are evaluated from the measured data of the COHERENT CsI and Ar experiments. Complete coherency and decoherency conditions are excluded by the CsI data with $p {=} 0.004$ at $q^2 {=} 3.1 {\times} 10^{3} ~ {\rm MeV^2}$ and with $p {=} 0.016$ at $q^2 {=} 2.3 {\times} 10^{3} ~ {\rm MeV^2}$, respectively, verifying that both QM superpositions and nuclear many-body effects contribute to $\nu {\rm A}_{el}$ interactions., Comment: V2 Published Version, 10 pages, 10 figures

We report the performance and characterization of a custom-built hybrid neutron detector (HND). The HND consists of BC501A liquid and BC702 phosphor powder scintillation neutron detectors, which is sensitive for the fast and thermal neutrons, respectively. Software analysis packages are developed to derive the energy spectra and compare with measured ones. Position variation of the Compton edge, the maximum probability and the location of the half-maximum intensity for the different γ-peaks of various sources (i.e., 22Na, 60Co, 137Cs) used in this study is presented.

We report on the measurements of the fluxes and spectra of the environmental fast neutron background at the China Jinping Underground Laboratory (CJPL) with a rock overburden of about 6700 meters water equivalent, using a liquid scintillator detector doped with 0.5% gadolinium. The signature of a prompt nuclear recoil followed by a delayed high energy $\gamma$-ray cascade is used to identify neutron events. The large energy deposition of the delayed $\gamma$-rays from the $(n, \gamma)$ reaction on gadolinium, together with the excellent n-$\gamma$ discrimination capability provides a powerful background suppression which allows the measurement of a low intensity neutron flux. The neutron flux of $(1.51\pm0.03(stat.)\pm0.10(syst.))\times10^{-7}$ cm$^{-2}$s$^{-1}$ in the energy range of 1 -- 10 MeV in the Hall A of CJPL was measured based on 356 days of data. In the same energy region, measurement with the same detector placed in a one meter thick polyethylene room gives a significantly lower flux of $(4.9\pm0.9(stat.)\pm0.5(syst.))\times10^{-9}$ cm$^{-2}$s$^{-1}$ with 174 days of data. This represents a measurement of the lowest environmental fast neutron background among the underground laboratories in the world, prior to additional experiment-specific attenuation. Additionally, the fast neutron spectra both in the Hall A and the polyethylene room were reconstructed with the help of GEANT4 simulation., Comment: 11 pages, 11 figures, 3 tables, Submitted to NIM-A

Status of search of coherent elastic neutrino-nucleus scattering (CEνNS) for reactor neutrino flux at Kuo-Sheng nuclear laboratory is discussed. Different detector candidates being used for CEνNS detection across the globe while Germanium detector with its well matured technology and sub-keV threshold, seem to open unseen experimental approach to CEνNS is widely discussed. Reactor neutrinos having energy below 10 MeV are ideal source for the study of CEνNS interaction. We studied about the possible CEνNS signals with associated uncertainties and limit on percentage of channeled nuclei in germanium crystal is quoted. Detection of flavourless CEνNS interaction can play a key role to open the new window on understanding of some unknown processes of the nature.

The p-type point-contact germanium detectors have been adopted for light dark matter WIMP searches and the studies of low energy neutrino physics. These detectors exhibit anomalous behavior to events located at the surface layer. The previous spectral shape method to identify these surface events from the bulk signals relies on spectral shape assumptions and the use of external calibration sources. We report an improved method in separating them by taking the ratios among different categories of in situ event samples as calibration sources. Data from CDEX-1 and TEXONO experiments are re-examined using the ratio method. Results are shown to be consistent with the spectral shape method., Comment: 29 pages, 16 figures

Germanium ionization detectors having sensitivities as low as 100 eV open new windows for the studies of neutrino and dark matter physics. This novel detector demands overcoming several challenges at both hardware and software levels. The amplitude of physics signals is comparable to those due to fluctuations of the pedestal electronic noise in low energy range. Therefore, it is important to study the low energy calibration properly. In this article, we focus on the optimization of the calibration scheme.

The China Jinping Underground Laboratory, inaugurated in 2010, is an underground research facility with the deepest rock overburden and largest space by volume in the world. The first-generation science programs include dark matter searches conducted by the CDEX and PandaX experiments. These activities are complemented by measurements of ambient radioactivity and installation of low-background counting systems. Phase II of the facility is being constructed, and its potential research projects are being formulated. In this review, we discuss the history, key features, results, and status of this facility and its experimental programs, as well as their future evolution and plans., 19 pages, 11 figures

To observe the neutrino–nucleus coherent scattering as well as for dark matter search, a detection system with ultra-low energy high purity germanium detector has been set up by the TEXONO Collaboration in Kuo-Sheng Nuclear Power Plant. Owing to the weak nature and small recoil energy of these rare events, understanding of background sources and their contribution to the energy spectrum are the key factors in this experiment. In this report, we will focus in detail on the different sources of backgrounds in the TEXONO experiment and the techniques used to reject/minimize them.

We present the improved constraints on couplings of solar axions and more generic bosonic dark matter particles using 737.1 kg-days of data from the CDEX-1B experiment. The CDEX-1B experiment, located at the China Jinping Underground Laboratory, primarily aims at the direct detection of weakly interacting massive particles using a p-type point-contact germanium detector. We adopt the profile likelihood ratio method for analysis of data in the presence of backgrounds. An energy threshold of 160 eV was achieved, much better than the 475 eV of CDEX-1A with an exposure of 335.6 kg-days. This significantly improves the sensitivity for the bosonic dark matter below 0.8 keV among germanium detectors. Limits are also placed on the coupling $g_{Ae} < 2.48 \times 10^{-11}$ from Compton, bremsstrahlung, atomic-recombination and de-excitation channels and $g^{eff}_{AN} \times g_{Ae} < 4.14 \times 10^{-17}$ from a $^{57}$Fe M1 transition at 90\% confidence level., version accepted by PRD, 9 pages, 11 figures

Next-generation xenon detectors with multiton-year exposure are powerful direct probes of dark matter candidates, in particular the favorite weakly interacting massive particles. Coupled with the features of low thresholds and backgrounds, they are also excellent telescopes of solar neutrinos. In this paper, we study the discovery potential of ton-scale xenon detectors in electromagnetic moments of solar neutrinos. Relevant neutrino-atom scattering processes are calculated by applying a state-of-the-art atomic many-body method—relativistic random phase approximation. Limits on these moments are derived from existing data and estimated with future experiment specifications. With one ton-year exposure, XENON-1T can improve the effective millicharge constraint by a factor of 2. With LZ and DARWIN, the projected improvement on the solar neutrino effective millicharge (magnetic moment) is around 7 (2) times smaller than the current bound. If LZ can keep the same background level and push the electron recoil threshold to 0.5 keV, the projected improvement on the millicharge (magnetic moment) is about 10 (3) times smaller than the current bound. An unconventional setup of placing a strong Cr51 neutrino source by a ton-scale xenon detector is also considered.

We report results on the searches of weakly interacting massive particles (WIMPs) with sub-GeV masses ($m_{\chi}$) via WIMP-nucleus spin-independent scattering with Migdal effect incorporated. Analysis on time-integrated (TI) and annual modulation (AM) effects on CDEX-1B data are performed, with 737.1 kg$\cdot$day exposure and 160 eVee threshold for TI analysis, and 1107.5 kg$\cdot$day exposure and 250 eVee threshold for AM analysis. The sensitive windows in $m_{\chi}$ are expanded by an order of magnitude to lower DM masses with Migdal effect incorporated. New limits on $\sigma_{\chi N}^{\rm SI}$ at 90\% confidence level are derived as $2\times$10$^{-32}\sim7\times$10$^{-35}$ $\rm cm^2$ for TI analysis at $m_{\chi}\sim$ 50$-$180 MeV/$c^2$, and $3\times$10$^{-32}\sim9\times$10$^{-38}$ $\rm cm^2$ for AM analysis at $m_{\chi}\sim$75 MeV/$c^2-$3.0 GeV/$c^2$., Comment: 5 pages, 4 figures

With the introduction of PAM-4 signaling at 56Gb/s and the decreased benefits of CMOS scaling for high-speed mixed-signal designs, SerDes designers and system architects are faced with severe performance versus power budget constraints. Power management and energy efficiency have become the main drivers for system design. However, industry standards such as EEE have failed to keep up with efficiency demands. In this context the choice between a so-called analog mixed signal (AMS) SerDes architecture vs. an ADC-DSP-based one has been debated at length. AMS provides significantly lower maximum power [2, 4] while ADC-DSP provides higher link margin [1] thus avoiding expensive and power hungry repeater ICs that largely negate the power advantage of AMS SerDes in a system. AMS provides an easier and cheaper approach to implement multi-tap DFEs [3] compared to DSP where it is typically very expensive to implement more than a 1-tap DFE. This paper will show an ADC-DSP SerDes transceiver with a 2-tap DFE is capable of operating error-free over a 38dB link yet having an overall power budget similar to AMS. The same basic SerDes architecture is implemented (Fig. 6.2.1) with minor differences in 16nm and 7nm FinFET, however, power scaling is incorporated into the 7nm version only.

Tremendous efforts are required to scale the summit of observing neutrinoless double beta decay ($0 \nu \beta \beta$). This article quantitatively explores the interplay between exposure (target mass X data taking time) and background levels in $0 \nu \beta \beta$ experiments. In particular, background reduction can substantially alleviate the necessity of unrealistic large exposure as the normal mass hierarchy (NH) is probed. The non-degenerate (ND)-NH can be covered with an exposure of O(100) ton-year, which is only an order of magnitude larger than those planned for next generation projects - provided that the background could be reduced by 0($10^{-6}$) relative to the current best levels. It follows that background suppression will be playing increasingly important and investment-effective, if not determining, roles in future $0 \nu \beta \beta$ experiments with sensitivity goals of approaching and covering ND-NH., Comment: V2 Published Version: 10 pages, 9 figures, 4 tables

Germanium detectors with sub-keV sensitivities can probe low-mass WIMP Dark Matter. This experimental approach is pursued at Kuo-Sheng Neutrino Laboratory (KSNL) in Taiwan and at China Jinping Underground Laboratory (CJPL) in China via TEXONO and CDEX programs, respectively. The highlights of R&D efforts on point contact germanium detectors and in particular the differentiation of surface and bulk events by pulse shape analysis are described. The latest results on WIMP-nucleon scattering cross-sections are also presented. Some of the allowed parameter space implied by other experiments are probed and excluded.

Elastic scattering of neutrino with nucleus (v Ael ) is the well defined weak interaction processes in the Standard Model. The TEXONO collaboration adopt electro-cooled point contact Germanium detector technology with sub-keV sensitivities for the detection of v Ael with reactor neutrinos. The detection of v Ael cross-section is beneficial in studies of irreducible background in dark matter experiments, study of Solar and Supernova processes, etc. It also provides the probe the quantum mechanical coherence effects in electroweak interactions. We defined a parameter α to measure degree of coherency in v Ael . Reactor neutrinos are found to be one of the best candidates to probe v Ael with high coherency. The divergence from full coherence leads to the study of neutron density distribution and to constrain the sensitivities in probing physics beyond the Standard Model.

Germanium detectors with point contact configuration is an exciting detector technology which provides sub-keV sensitivities as low as 100 eVee with kg-scale detector mass. This detector technique offers a unique opportunity to realize experiments on dark matter, to enhance the sensitivity of electromagnetic properties of neutrino and coherent elastic scattering of neutrino nucleus with reactor neutrino source. The TEXONO collaboration have been pursuing this research program at the Kuo-Sheng Neutrino Laboratory (KSNL) in Taiwan. We will highlight our results on neutrino electromagnetic properties, search of sterile neutrinos, as well as studies towards observation of neutrino-nucleus coherent scattering. The detector R&D programs which allow us to experimentally probe this new energy window will be discussed. The efforts set the stage and complement the CDEX dark matter experiment at the new China Jinping Underground Laboratory (CJPL) in China.

We report in situ neutron background measurements at the Kuo-Sheng Reactor Neutrino Laboratory (KSNL) by a hybrid neutron detector (HND) with a data size of 33.8 days under identical shielding configurations as during the neutrino physics data taking. The HND consists of BC-501A liquid and BC-702 phosphor powder scintillation neutron detectors, which is sensitive to both fast and thermal neutrons, respectively. Neutron-induced events for the two channels are identified and differentiated by pulse shape analysis, such that background of both are simultaneously measured. The fast neutron fluxes are derived by an iterative unfolding algorithm. Neutron induced background in the germanium detector under the same fluxes, both due to cosmic-rays and ambient radioactivity, are derived and compared with the measurements. The results are valuable to background understanding of the neutrino data at the KSNL. In particular, neutron-induced background events due to ambient radioactivity as well as from reactor operation are negligible compared to intrinsic cosmogenic activity and ambient $\gamma$-activity. The detector concept and analysis procedures are applicable to neutron background characterization in similar rare-event experiments., Comment: 12 pages, 29 figures

We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8×10^{-42} and 3×10^{-36} cm^{2} at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (m_{χ}) of 5 GeV/c^{2} are achieved. The lower reach of m_{χ} is extended to 2 GeV/c^{2}.

A study on cosmogenic activation in germanium was carried out to evaluate the cosmogenic background level of natural and $^{70}$Ge depleted germanium detectors. The production rates of long-lived radionuclides were calculated with Geant4 and CRY. Results were validated by comparing the simulated and experimental spectra of CDEX-1B detector. Based on the validated codes, the cosmogenic background level was predicted for further tonne-scale CDEX experiment. The suppression of cosmogenic background level could be achieved by underground germanium crystal growth and high-purity germanium detector fabrication to reach the sensitivity requirement for direct detection of dark matter. With the low cosmogenic background, new physics channels, such as solar neutrino research and neutrinoless double-beta decay experiments, were opened and the corresponding simulations and evaluations were carried out., Version accepted by SCPMA; 10 pages, 13 figures, 7 tables

We report results from searches of pseudoscalar and vector bosonic super-weakly interacting massive particles (super-WIMP) in the TEXONO experiment at the Kuo-Sheng Nuclear Power Station, using 314.15 kg days of data from $n$-type Point-Contact Germanium detector. The super-WIMPs are absorbed and deposit total energy in the detector, such that the experimental signatures are spectral peaks corresponding to the super-WIMP mass. Measured data are compatible with the background model, and no significant excess of super-WIMP signals are observed. We derived new upper limits on couplings of electrons with the pseudoscalar and vector bosonic super-WIMPs in the sub-keV mass region, assuming they are the dominant contributions to the dark matter density of our galaxy., Comment: 23 pages, 17 figures

Point-Contact Germanium detectors (PCGe) are novel techniques which offer sub-keV sensitivities radiation senors with kg-scale mass. The TEXONO and CDEX Collaborations have been pursuing research program on neutrino properties at the Kuo-Sheng Neutrino Laboratory (KSNL) in Taiwan and on WIMP dark matter in the China Jinping Underground Laboratory (CJPL) in China, respectively. We present highlights of our physics program on the studies of electromagnetic interactions neutrino at KSNL.

We report the performance and characterization of a custom-built hybrid detector consisting of BC501A liquid scintillator for fast neutrons and BC702 scintillator for thermal neutrons. The calibration and the resolution of the BC501A liquid scintillator detector are performed. The event identification via Pulse Shape Discrimination (PSD) technique is developed in order to distinguish gamma, fast and thermal neutrons. Monte Carlo simulation packages are developed in GEANT4 to obtain actual neutron energy spectrum from the measured recoil spectrum. The developed methods are tested by reconstruction of 241AmBe(\alpha, n) neutron spectrum., Comment: 12 pages, 32 figures

Constraints on couplings of several Beyond Standard Model Physics scenarios, mediated by massive intermediate particles including (1) Extra Z-prime, (2) New Light Spin-1 Boson, and (3) Charged Higgs Boson, are placed via neutrino-electron scattering channel to test Standard Model at low energy-momentum transfer regime. Data on $\bar{\nu}_{e}-e$ and $\nu_{e}-e$ scattering from the TEXONO and LSND Experiments, respectively, are used. Upper bounds to coupling constants of Flavor Conserving and Flavor Violating New Light Spin-1 Boson and Charged Higgs Boson with respect to different mediator masses are determined. The relevant parameter spaces are extended by allowing light mediators. New lower mass limits for extra Z-prime gauge boson models are also placed., Comment: 14 pages, 29 figures

We report the results of searches for solar axions and galactic dark matter axions or axion-like particles with CDEX-1 experiment at the China Jinping Underground Laboratory, using 335.6 kg-days of data from a p-type point-contact germanium detector. The data are compatible with the background model and no excess signals are observed. Limits of solar axions on the model independent coupling $g_{Ae}

Neutrino-electron scattering is a purely leptonic fundamental interaction and therefore provides an important channel to test the Standard Model, especially at the low energy-momentum transfer regime. We derived constraints on neutrino nonstardard interaction couplings depending on model-independent approaches which are described by a four-Fermi pointlike interaction and unparticle physics model with tensorial components. Data on $\bar{\nu}_{e}-e$ and $\nu_{e}-e$ scattering from the TEXONO and LSND experiments, respectively, are used. The upper limits and the allowed regions of scalar, pseudoscalar, and tensorial nonstandard interaction couplings of neutrinos are derived at 90\% confidence level in both one-parameter and two-parameter analysis. New upper limits for tensorial unparticle physics coupling constants and mass parameters are also placed., Comment: 9 pages, 10 figures

Germanium detectors with sub-keV sensitivities open a window to study neutrino physics to search for light weakly interacting massive particle (WIMP) dark matter. We summarize the recent results on spin-independent couplings of light WIMPs from the TEXONO experiment at the Kuo-Sheng Reactor Neutrino Laboratory. Highlights of the physics motivation, our R&D programme, as well as the status and plans are presented.

Germanium detectors with sub-keV sensitivities open a window to search for low-mass WIMP dark matter. The latest limit on spin-independent couplings from the TEXONO experiment at the Kuo-Sheng Reactor Neutrino Laboratory is reported. Highlights of our R&D program, as well as the status and plans are discussed.

The characteristics of the surface inactive layer of a 1-kg-mass p-type point-contact germanium detector were studied. The thickness of the inactive layer and its uniformity on the top and lateral surfaces were measured. A charge collection efficiency function was developed according to the Monte Carlo simulation to describe the charge collection capacity along the depth within this inactive layer. In the energy range below 18 keV, the surface, bulk, and total spectra of 57 Co, 133 Ba, 137 Cs, and 60 Co from simulations based on the charge collection efficiency function were well consistent with those from experiments.

The China Jinping Underground Laboratory (CJPL) is a new facility for conducting low event-rate experiments. We present an overview of CJPL and the CDEX Dark Matter program based on germanium detectors with sub-keV sensitivities. The achieved results, status as well as the R&D and technology acquisition efforts towards a ton-scale experiment are reported., 6 pages, 5 figures; Contributions to Proceedings of TAUP-2015 Conference

The transition magnetic moment of a sterile-to-active neutrino conversion gives rise to not only radiative decay of a sterile neutrino, but also its non-standard interaction (NSI) with matter. For sterile neutrinos of keV-mass as dark matter candidates, their decay signals are actively searched for in cosmic X-ray spectra. In this work, we consider the NSI that leads to atomic ionization, which can be detected by direct dark matter experiments. It is found that this inelastic scattering process for a nonrelativistic sterile neutrino has a pronounced enhancement in the differential cross section at energy transfer about half of its mass, manifesting experimentally as peaks in the measurable energy spectra. The enhancement effects gradually smear out as the sterile neutrino becomes relativistic. Using data taken with germanium detectors that have fine energy resolution in keV and sub-keV regimes, constraints on sterile neutrino mass and its transition magnetic moment are derived and compared with those from astrophysical observations.

Neutrino-nucleus elastic scattering provides a unique laboratory to study the quantum mechanical coherency effects in electroweak interactions, towards which several experimental programs are being actively pursued. We report results of our quantitative studies on the transitions towards decoherency. A parameter ($\alpha$) is identified to describe the degree of coherency, and its variations with incoming neutrino energy, detector threshold and target nucleus are studied. The ranges of $\alpha$ which can be probed with realistic neutrino experiments are derived, indicating complementarity between projects with different sources and targets. Uncertainties in nuclear physics and in $\alpha$ would constrain sensitivities in probing physics beyond the standard model. The maximum neutrino energies corresponding to $\alpha$>0.95 are derived., Comment: 5 pages, 4 figures, 3 tables. V2 -- Published Version

A 994g mass p-type PCGe detector was deployed by the first phase of the China Dark matter EXperiment aiming at the direct searches of light weakly interacting massive particles. Measuring the thickness of the dead layer of a p-type germanium detector is an issue of major importance since it determines the fiducial mass of the detector. This work reports a method using an uncollimated 133Ba source to determine the dead layer thickness. The experimental design, data analysis and Monte Carlo simulation processes, as well as the statistical and systematic errors are described. An agreement between the experimental data and simulation results was achieved to derive the thickness of the dead layer of 1.02 mm., Comment: 7 pages, 9 figures

The TEXONO-CDEX Collaboration (Taiwan experiment on neutrino–China dark matter experiment) explores high-purity germanium (HPGe) detection technology to develop a sub-keV threshold detector for pursuing studies on low mass weakly interacting massive particles (WIMPs), properties of neutrino and the possibilities of neutrino-nucleus coherent scattering observation. This article will introduce the facilities of newly established China Jing-Ping Underground Laboratory (CJPL), preliminary result of cosmic ray background studies at CJPL, the dark matter studies pursued at Kuo-Sheng Neutrino Laboratory (KSNL) and research efforts to accomplish our physics goals.

The article describes the research program towards an experiment to observe coherent scattering between neutrinos and the nucleus at the power reactor. The motivations of studying this process are surveyed. In particular, a threshold of 100–200 eV has been achieved with an ultra-low-energy germanium detector prototype. This detection capability at low energy can also be adapted for searches of Cold Dark Matter in the low-mass region as well as to enhance the sensitivities in the study of neutrino magnetic moments.

The theme of the TEXONO-CDEX research program is on the studies of low energy neutrino and dark matter physics at Kuo-Sheng Reactor Neutrino Laboratory and China Jin-Ping Underground Laboratory. The current goal is to open the "sub-keV" detector window with germanium detectors. The three main scientific subjects are neutrino magnetic moments, neutrino-nucleus coherent scattering, and dark matter searches. We highlight the status, results and plans in this article.