Two-neutrino double electron capture is a process allowed in the Standard Model of Particle Physics. This rare decay has been observed in \(^{78}\)Kr, \(^{130}\)Ba and more recently in \(^{124}\)Xe. ...In this publication we report on the search for this process in \(^{124}\)Xe and \(^{126}\)Xe using the full exposure of the Large Underground Xenon (LUX) experiment, in a total of of 27769.5~kg-days. No evidence of a signal was observed, allowing us to set 90\% C.L. lower limits for the half-lives of these decays of \(2.0\times10^{21}\)~years for \(^{124}\)Xe and \(1.9\times10^{21}\)~years for \(^{126}\)Xe.
The Large Underground Xenon (LUX) dark matter search was a 250-kg active mass dual-phase time projection chamber that operated by detecting light and ionization signals from particles incident on a ...xenon target. In December 2015, LUX reported a minimum 90% upper C.L. of 6e-46 cm^2 on the spin-independent WIMP-nucleon elastic scattering cross section based on a 1.4e4 kg*day exposure in its first science run. Tension between experiments and the absence of a definitive positive detection suggest it would be prudent to search for WIMPs outside the standard spin-independent/spin-dependent paradigm. Recent theoretical work has identified a complete basis of 14 independent effective field theory (EFT) operators to describe WIMP-nucleon interactions. In addition to spin-independent and spin-dependent nuclear responses, these operators can produce novel responses such as angular-momentum-dependent and spin-orbit couplings. Here we report on a search for all 14 of these EFT couplings with data from LUX's first science run. Limits are placed on each coupling as a function of WIMP mass.
We present the results of a direct detection search for mirror dark matter interactions, using data collected from the Large Underground Xenon experiment during 2013, with an exposure of 95 live-days ...\(\times\) 118 kg. Here, the calculations of the mirror electron scattering rate in liquid xenon take into account the shielding effects from mirror dark matter captured within the Earth. Annual and diurnal modulation of the dark matter flux and atomic shell effects in xenon are also accounted for. Having found no evidence for an electron recoil signal induced by mirror dark matter interactions we place an upper limit on the kinetic mixing parameter over a range of local mirror electron temperatures between 0.1 and 0.6 keV. This limit shows significant improvement over the previous experimental constraint from orthopositronium decays and significantly reduces the allowed parameter space for the model. We exclude mirror electron temperatures above 0.3 keV at a 90% confidence level, for this model, and constrain the kinetic mixing below this temperature.
We present a novel analysis technique for liquid xenon time projection chambers that allows for a lower threshold by relying on events with a prompt scintillation signal consisting of single detected ...photons. The energy threshold of the LUX dark matter experiment is primarily determined by the smallest scintillation response detectable, which previously required a 2-fold coincidence signal in its photomultiplier arrays, enforced in data analysis. The technique presented here exploits the double photoelectron emission effect observed in some photomultiplier models at vacuum ultraviolet wavelengths. We demonstrate this analysis using an electron recoil calibration dataset and place new constraints on the spin-independent scattering cross section of weakly interacting massive particles (WIMPs) down to 2.5 GeV/c\(^2\) WIMP mass using the 2013 LUX dataset. This new technique is promising to enhance light WIMP and astrophysical neutrino searches in next-generation liquid xenon experiments.
Phys. Rev. C 102, 014602 (2020) The LUX-ZEPLIN (LZ) experiment will enable a neutrinoless double beta decay
search in parallel to the main science goal of discovering dark matter particle
...interactions. We report the expected LZ sensitivity to $^{136}$Xe neutrinoless
double beta decay, taking advantage of the significant ($>$600 kg) $^{136}$Xe
mass contained within the active volume of LZ without isotopic enrichment.
After 1000 live-days, the median exclusion sensitivity to the half-life of
$^{136}$Xe is projected to be 1.06$\times$10$^{26}$ years (90% confidence
level), similar to existing constraints. We also report the expected
sensitivity of a possible subsequent dedicated exposure using 90% enrichment
with $^{136}$Xe at 1.06$\times$10$^{27}$ years.
Journal of Instrumentation, Volume 15, February 2020 We report here methods and techniques for creating and improving a model that
reproduces the scintillation and ionization response of a dual-phase ...liquid and
gaseous xenon time-projection chamber. Starting with the recent release of the
Noble Element Simulation Technique (NEST v2.0), electronic recoil data from the
$\beta$ decays of ^3$H and ^{14}$C in the Large Underground Xenon (LUX)
detector were used to tune the model, in addition to external data sets that
allow for extrapolation beyond the LUX data-taking conditions. This paper also
presents techniques used for modeling complicated temporal and spatial detector
pathologies that can adversely affect data using a simplified model framework.
The methods outlined in this report show an example of the robust applications
possible with NEST v2.0, while also providing the final electronic recoil model
and detector parameters that will used in the new analysis package, the LUX
Legacy Analysis Monte Carlo Application (LLAMA), for accurate reproduction of
the LUX data. As accurate background reproduction is crucial for the success of
rare-event searches, such as dark matter direct detection experiments, the
techniques outlined here can be used in other single-phase and dual-phase xenon
detectors to assist with accurate ER background reproduction.
We report results from an extensive set of measurements of the \b{eta}-decay response in liquid xenon.These measurements are derived from high-statistics calibration data from injected sources of ...both \(^{3}\)H and \(^{14}\)C in the LUX detector. The mean light-to-charge ratio is reported for 13 electric field values ranging from 43 to 491 V/cm, and for energies ranging from 1.5 to 145 keV.
The scattering of dark matter (DM) particles with sub-GeV masses off nuclei is difficult to detect using liquid xenon-based DM search instruments because the energy transfer during nuclear recoils is ...smaller than the typical detector threshold. However, the tree-level DM-nucleus scattering diagram can be accompanied by simultaneous emission of a Bremsstrahlung photon or a so-called "Migdal" electron. These provide an electron recoil component to the experimental signature at higher energies than the corresponding nuclear recoil. The presence of this signature allows liquid xenon detectors to use both the scintillation and the ionization signals in the analysis where the nuclear recoil signal would not be otherwise visible. We report constraints on spin-independent DM-nucleon scattering for DM particles with masses of 0.4-5 GeV/c\(^2\) using 1.4\(\times10^4\) kg\(\cdot\)day of search exposure from the 2013 data from the Large Underground Xenon (LUX) experiment for four different classes of mediators. This analysis extends the reach of liquid xenon-based DM search instruments to lower DM masses than has been achieved previously.
This article addresses pigmentary disorders relevant to India. Many of these disorders are easily spotted because of the Indians' darker complexion. The authors examine hypopigmentary and ...hyperpigmentary disorders, defining the main characteristics of each and their relevance to the people of India, including social as well as physical ramifications. The authors propose the treatments available to Indians exhibiting these skin disorders.
Various dark matter models predict annual and diurnal modulations of dark matter interaction rates in Earth-based experiments as a result of the Earth's motion in the halo. Observation of such ...features can provide generic evidence for detection of dark matter interactions. This paper reports a search for both annual and diurnal rate modulations in the LUX dark matter experiment using over 20 calendar months of data acquired between 2013 and 2016. This search focuses on electron recoil events at low energies, where leptophilic dark matter interactions are expected to occur and where the DAMA experiment has observed a strong rate modulation for over two decades. By using the innermost volume of the LUX detector and developing robust cuts and corrections, we obtained a stable event rate of 2.3\(\pm\)0.2~cpd/keV\(_{\text{ee}}\)/tonne, which is among the lowest in all dark matter experiments. No statistically significant annual modulation was observed in energy windows up to 26~keV\(_{\text{ee}}\). Between 2 and 6~keV\(_{\text{ee}}\), this analysis demonstrates the most sensitive annual modulation search up to date, with 9.2\(\sigma\) tension with the DAMA/LIBRA result. We also report no observation of diurnal modulations above 0.2~cpd/keV\(_{\text{ee}}\)/tonne amplitude between 2 and 6~keV\(_{\text{ee}}\).
