arXiv subjects

Lakhwinder Singh

Publications and source records attributed to Lakhwinder Singh.

18 recordsLinked to original sources

arXiv2026

Many-body atomic response functions of xenon and germanium for leading-order sub-GeV dark matter-electron interactions in effective field theory

Direct searches of dark matter candidates with mass energies less than 1 GeV is an active research field. The energy depositions are comparable to the scale of atomic, molecular, or condensed matter systems, therefore many-body physics plays an important role in understanding the detector's response in dark matter scattering. We present in this work a comprehensive data set of atomic response functions for xenon and germanium with 12.2 and 80 eV energy thresholds, respectively, using the (multiconfiguration) relativistic random phase approximation. This approach takes into account the relativistic, exchange, and correlation effects in one self-consistent framework, and is benchmarked successfully by photoabsorption data from thresholds to 30 keV with $\lesssim5\%$ errors. Comparisons with our previous and some other independent particle approaches in literature are made. It is also found that the spin-dependent (SD) response has significant difference from the spin-independent (SI) one such that the dark matter SD and SI interactions with electrons can be distinguished in unpolarized scattering, which is typical for direct search detectors. Finally, the exclusion limits set by current experiments are updated with our new results.

astro-ph.CO↗

arXiv2026

Unified framework for precise background modeling to enhance rare event detection at the Kuo-Sheng nuclear reactor laboratory

A comprehensive GEANT4 simulation framework was developed to model the background of the TEXONO experiment, including contributions from radioactive isotopes in detector components and the surrounding environment. The HPGe detector front-end electronics (pre-amplifier) were modeled with trace amounts of naturally occurring radionuclides 238U, 232Th, and 235U from manufacturing materials. Results show that the 238U and 232Th decay chains dominate the background below 400 keV, each contributing O(1) counts kg^-1 keV^-1 day^-1. Trace impurities were also introduced into the anti-Compton veto (ACV) detectors to represent realistic materials: 40K in the NaI(Tl) crystal and 137Cs in the CsI(Tl) detector. Simulations identified measurable background contributions from both isotopes, with the residual spectrum dominated by 40K gamma-rays and smaller contributions from 137Cs. The 40K background rate is about 0.1 counts kg^-1 keV^-1 day^-1, nearly 10 times larger than that from 137Cs below 400 keV. Environmental radioactivity was modeled using 60Co, 54Mn, and 135Xe distributed in the air gap between the copper end-cap and the NaI(Tl) ACV detector, representing airborne and surface contamination. These sources contribute minor background components below 100 keV, at levels of about 10^-2, 10^-2, and 0.1 counts kg^-1 keV^-1 day^-1 for 135Xe, 54Mn, and 60Co, respectively. Comparison of simulated and measured spectra shows good overall agreement, with only minor deviations at specific gamma-lines, validating the background model and demonstrating the robustness of the simulation framework for detector and shielding design.

hep-ex↗

arXiv2024

Exploring Non-Isotropic Lorentz Invariance Violation Through Sidereal Effect at DUNE

Lorentz Invariance Violation (LIV) presents an intriguing opportunity to investigate fundamental symmetries, with neutrinos serving as a particularly effective probe for this phenomenon. Long-baseline neutrino experiments, such as the Deep Underground Neutrino Experiment (DUNE), excel at exploring non-isotropic LIV, especially through the observation of sidereal effects. This study comprehensively examines the full parameter space of non-isotropic, non-diagonal LIV parameters with sidereal dependence, focusing on two distinct flux scenarios: a low-energy flux and a tau-optimized flux. Through this analysis, we derive more stringent constraints on LIV parameters. Our results indicate that DUNE may achieve enhanced sensitivity for some LIV parameters, exceeding all previously established limits and marking a significant advancement in the investigation of LIV.

hep-ph↗

arXiv2024

Octant Ambiguity in the Presence of Non-isotropic Lorentz Invariance Violation

Global analyses of neutrino data suggest that the mixing angle $θ_{23}$ is likely to be nonmaximal with two closely matched solutions emerging: one representing a smaller angle ($θ_{23}$ < $π/4$) and the other a larger angle ($θ_{23}$ > $π/4$). This ambiguity, known as the octant ambiguity of $θ_{23}$, presents a significant challenge in neutrino research and is a primary objective of future long-baseline experiments. In this study, for the first time, we explore how non-isotropic Lorentz violation affects measurements of mixing angle $θ_{23}$, with a particular emphasis on sidereal effects in the Deep Underground Neutrino Experiment. Our findings reveal that ability of DUNE to resolve the octant ambiguity is significantly compromised in the presence of the $c^{xy}_{e τ}$ parameter. Furthermore, we demonstrate that LIV exacerbates the degeneracy between the Dirac CP-phase $δ_{cp}$ and $θ_{23}$.

hep-ph↗

arXiv2024

Investigating Lorentz Invariance Violation Effects on CP Violation and Mass Hierarchy sensitivity at DUNE

One of the current goals of neutrino experiments is to precisely determine standard unknown oscillation parameters such as the leptonic CP phase and mass hierarchy. Lorentz invariance violation represents a potential physics factor that could influence the experiment's ability to achieve these precise determinations. This study investigates the influence of Lorentz invariance violation (LIV) on oscillation dynamics, particularly through non-isotropic CPT-violating ($a^{X}_{eμ}$, $a^{X}_{eτ}$, $a^{X}_{μτ}$) and CPT-conserving ($c^{XY}_{eμ}$, $c^{XY}_{e τ}$, $c^{XY}_{μτ}$) parameters within the Deep Underground Neutrino Experiment (DUNE). We analyze the impact of these parameters on the mass hierarchy (MH) and Dirac CP phase sensitivity measurements. Our findings indicate that while MH sensitivity remains relatively unaffected, only the presence of $c^{XY}_{μτ}$ significantly deteriorates MH sensitivity, albeit remaining above the $5 σ$ threshold. Additionally, we observe a substantial compromise in CP sensitivity due to the $c^{XY}_{e μ}$ and $c^{XY}_{e τ}$ parameters.

hep-ph↗

arXiv2023

Search for Lorentz-violation through sidereal effect at NOνA Experiment

Long-baseline neutrino oscillation experiments offer a unique laboratory to test the fundamental Lorentz symmetry, which is heart of both the standard model of particle and general relativity theory. Deviations from the standard neutrino oscillation or the sidereal modulation in neutrino events will smoking-gun experimental signature of Lorentz and CPT violation. In this study, we investigate the impact of the sidereal effect on standard neutrino oscillation measurements within the context of the NOνA experiment. Additionally, we assess the sensitivity of the NOνA experiment to detect Lorentz-violating interactions, taking into account the sidereal effect. Furthermore, we highlight potential of the NOνA experiment to set the new constraints on anisotropic Lorentz-violating parameters.

hep-ph↗

arXiv2021

Constraints from a many-body method on spin-independent dark matter scattering off electrons using data from germanium and xenon detectors

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.

hep-ph↗

arXiv2021

Spin-dependent dark matter-electron interactions

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: $σ_e^{\textrm{(SD)}}<10^{-41}-10^{-40}\,\textrm{cm}^2$ are comparable to the ones drawn on DM-neutron and DM-proton at slightly bigger DM masses. The detector's responses to the LO SD and SI interactions are analyzed. In nonrelativistic limit, a constant ratio between them leads to an indistinguishability of the SD and SI recoil energy spectra. Relativistic calculations however show the scaling starts to break down at a few hundreds of eV, where spin-orbit effects become sizable. We discuss the prospects of disentangling the SI and SD components in DM-electron interactions via spectral shape measurements, as well as having spin-sensitive experimental signatures without SI background.

hep-ph↗

arXiv2019

Discovery potential of multi-ton xenon detectors in neutrino electromagnetic properties

Next-generation xenon detectors with multi-ton-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-arts atomic many-body method--relativistic random phase approximation (RRPA). 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 milli-charge constraint by a factor two. With LZ and DARWIN, the projected improvement on the solar neutrino effective milli-charge(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 milli-charge(magnetic moment) is about 10(3) times smaller than the current bound.

hep-ph↗

arXiv2019

Constraints on Bosonic Dark Matter with Low Threshold Germanium Detector at Kuo-Sheng Reactor Neutrino Laboratory

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.

hep-ex↗

arXiv2018

Required sensitivity to search the neutrinoless double beta decay in $^{124}Sn$

\textbf{T}he \textbf{IN}dia's \textbf{TIN} (TIN.TIN) detector is under development in the search for neutrinoless double-$β$ decay (0$νββ$) using 90\% enriched $^{124}$Sn isotope as the target mass. This detector will be housed in the upcoming underground facility of the \textbf{I}ndia based \textbf{N}eutrino \textbf{O}bservatory. 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 (2$νββ$) decay background is studied at various energy resolutions. The most optimistic and pessimistic scenario to probe the neutrino mass hierarchy at 3$σ$ sensitivity level and 90\% C.L. is also discussed.

hep-ph↗

arXiv2017

The first result on 76Ge neutrinoless double beta decay from CDEX-1 experiment

We report the first result on Ge-76 neutrinoless double beta decay from CDEX-1 experiment at China Jinping Underground Laboratory. A mass of 994 g p-type point-contact high purity germanium detector has been installed to search the neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg*day has been analyzed. The wideband spectrum from 500 keV to 3 MeV was obtained and the average event rate at the 2.039 MeV energy range is about 0.012 count per keV per kg per day. The half-life of Ge-76 neutrinoless double beta decay has been derived based on this result as: T 1/2 > 6.4*10^22 yr (90% C.L.). An upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved. The possible methods to further decrease the background level have been discussed and will be pursued in the next stage of CDEX experiment.

hep-ex↗

arXiv2016

Atomic ionization by sterile-to-active neutrino conversion and constraints on dark matter sterile neutrinos with germanium detectors

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.

hep-ph↗

arXiv2014

Constraining neutrino electromagnetic properties by germanium detectors

The electromagnetic properties of neutrinos, which are either trivial or negligible in the context of the Standard Model, can probe new physics and have significant implications in astrophysics and cosmology. The current best direct limits on the neutrino millicharges and magnetic moments are both derived from data taken with germanium detectors with low thresholds at keV levels. In this paper, we discuss in detail a robust, ab initio method: the multiconfiguration relativistic random phase approximation, that enables us to reliably understand the germanium detector response at the sub-keV level, where atomic many-body physics matters. Using existing data with sub-keV thresholds, limits on reactor antineutrino's millicharge, magnetic moment, and charge radius squared are derived. The projected sensitivities for next generation experiments are also given and discussed.

hep-ph↗

arXiv2014

Constraints on millicharged neutrinos via analysis of data from atomic ionizations with germanium detectors at sub-keV sensitivities

With the advent of detectors with sub-keV sensitivities, atomic ionization has been identified as a promising avenue to probe possible neutrino electromagnetic properties. The interaction cross-sections induced by millicharged neutrinos are evaluated with the ab-initio multi-configuration relativistic random-phase approximation. There is significant enhancement at atomic binding energies compared to that when the electrons are taken as free particles. Positive signals would distinctly manifest as peaks at specific energies with known intensity ratios. Selected reactor neutrino data with germanium detectors at analysis threshold as low as 300 eV are studied. No such signatures are observed, and a combined limit on the neutrino charge fraction of | \numq | < 1.0 X 10^{-12} at 90% confidence level is derived.

hep-ph↗

arXiv2014

Study of the material photon and electron background and the liquid argon detector veto efficiency of the CDEX-10 experiment

The China Dark Matter Experiment (CDEX) is located at the China Jinping underground laboratory (CJPL) and aims to directly detect the WIMP flux with high sensitivity in the low mass region. Here we present a study of the predicted photon and electron backgrounds including the background contribution of the structure materials of the germanium detector, the passive shielding materials, and the intrinsic radioactivity of the liquid argon that serves as an anti-Compton active shielding detector. A detailed geometry is modeled and the background contribution has been simulated based on the measured radioactivities of all possible components within the GEANT4 program. Then the photon and electron background level in the energy region of interest (<10^-2 events kg-1 day-1 keV-1 (cpkkd)) is predicted based on Monte Carlo simulations. The simulated result is consistent with the design goal of CDEX-10 experiment, 0.1 cpkkd, which shows that the active and passive shield design of CDEX-10 is effective and feasible.

physics.ins-det↗

arXiv2013

Atomic ionization of germanium due to neutrino magnetic moments

An ab initio calculation of atomic ionization of germanium (Ge) by neutrinos was carried out in the framework of multiconfiguration relativistic random phase approximation. The main goal is to provide a more accurate cross section formula than the conventional one, which is based on the free electron approximation, for searches of neutrino magnetic moments with Ge detectors whose threshold is reaching down to the sub-keV regime. Limits derived with both methods are compared, using reactor neutrino data taken with low threshold germanium detectors.

hep-ph↗

arXiv2013

The CDEX-1 1 kg Point-Contact Germanium Detector for Low Mass Dark Matter Searches

The CDEX Collaboration has been established for direct detection of light dark matter particles, using ultra-low energy threshold p-type point-contact germanium detectors, in China JinPing underground Laboratory (CJPL). The first 1 kg point-contact germanium detector with a sub-keV energy threshold has been tested in a passive shielding system located in CJPL. The outputs from both the point-contact p+ electrode and the outside n+ electrode make it possible to scan the lower energy range of less than 1 keV and at the same time to detect the higher energy range up to 3 MeV. The outputs from both p+ and n+ electrode may also provide a more powerful method for signal discrimination for dark matter experiment. Some key parameters, including energy resolution, dead time, decay times of internal X-rays, and system stability, have been tested and measured. The results show that the 1 kg point-contact germanium detector, together with its shielding system and electronics, can run smoothly with good performances. This detector system will be deployed for dark matter search experiments.

physics.ins-det↗