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Projected sensitivity of the LUX-ZEPLIN experiment to the 0νββ decay of Xe 136
The LUX-ZEPLIN (LZ) experiment will enable a neutrinoless double β decay search in parallel to the main science goal of discovering dark matter particle interactions. We report the expected LZ sensitivity to Xe136 neutrinoless double β decay, taking advantage of the significant (>600 kg) Xe136 mass contained within the active volume of LZ without isotopic enrichment. After 1000 live-days, the median exclusion sensitivity to the half-life of Xe136 is projected to be 1.06×1026 years (90% confidence level), similar to existing constraints. We also report the expected sensitivity of a possible subsequent dedicated exposure using 90% enrichment with Xe136 at 1.06×1027 years
Simulations of events for the LUX-ZEPLIN (LZ) dark matter experiment
The LUX-ZEPLIN dark matter search aims to achieve a sensitivity to the WIMP-nucleon spin-independent cross-section down to (1–2)×10−12 pb at a WIMP mass of 40 GeV/c2. This paper describes the simulations framework that, along with radioactivity measurements, was used to support this projection, and also to provide mock data for validating reconstruction and analysis software. Of particular note are the event generators, which allow us to model the background radiation, and the detector response physics used in the production of raw signals, which can be converted into digitized waveforms similar to data from the operational detector. Inclusion of the detector response allows us to process simulated data using the same analysis routines as developed to process the experimental data
Extending light WIMP searches to single scintillation photons in LUX
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 twofold 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/c2 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
A search for new physics in low-energy electron recoils from the first LZ exposure
The LUX-ZEPLIN (LZ) experiment is a dark matter detector centered on a
dual-phase xenon time projection chamber. We report searches for new physics
appearing through few-keV-scale electron recoils, using the experiment's first
exposure of 60 live days and a fiducial mass of 5.5t. The data are found to be
consistent with a background-only hypothesis, and limits are set on models for
new physics including solar axion electron coupling, solar neutrino magnetic
moment and millicharge, and electron couplings to galactic axion-like particles
and hidden photons. Similar limits are set on weakly interacting massive
particle (WIMP) dark matter producing signals through ionized atomic states
from the Migdal effect.Comment: 13 pages, 10 figures. See https://tinyurl.com/LZDataReleaseRun1ER for
a data release related to this pape
Fast and Flexible Analysis of Direct Dark Matter Search Data with Machine Learning
We present the results from combining machine learning with the profile
likelihood fit procedure, using data from the Large Underground Xenon (LUX)
dark matter experiment. This approach demonstrates reduction in computation
time by a factor of 30 when compared with the previous approach, without loss
of performance on real data. We establish its flexibility to capture non-linear
correlations between variables (such as smearing in light and charge signals
due to position variation) by achieving equal performance using pulse areas
with and without position-corrections applied. Its efficiency and scalability
furthermore enables searching for dark matter using additional variables
without significant computational burden. We demonstrate this by including a
light signal pulse shape variable alongside more traditional inputs such as
light and charge signal strengths. This technique can be exploited by future
dark matter experiments to make use of additional information, reduce
computational resources needed for signal searches and simulations, and make
inclusion of physical nuisance parameters in fits tractable
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