Improved Limits on Scattering of Weakly Interacting Massive Particles from Reanalysis of 2013 LUX data (1512.03506v3)

Abstract: We present constraints on weakly interacting massive particles (WIMP)-nucleus scattering from the 2013 data of the Large Underground Xenon dark matter experiment, including $1.4\times10^{4}\;\mathrm{kg\; day}$ of search exposure. This new analysis incorporates several advances: single-photon calibration at the scintillation wavelength, improved event-reconstruction algorithms, a revised background model including events originating on the detector walls in an enlarged fiducial volume, and new calibrations from decays of an injected tritium $\beta$ source and from kinematically constrained nuclear recoils down to 1.1 keV. Sensitivity, especially to low-mass WIMPs, is enhanced compared to our previous results which modeled the signal only above a 3 keV minimum energy. Under standard dark matter halo assumptions and in the mass range above 4 $\mathrm{GeV}\,c^{-2}$, these new results give the most stringent direct limits on the spin-independent WIMP-nucleon cross section. The 90% C.L. upper limit has a minimum of 0.6 zb at 33 $\mathrm{GeV}\,c^{-2}$ WIMP mass.

• The paper refines WIMP-nucleon scattering limits by reanalyzing 2013 LUX data using enhanced calibration and event-reconstruction techniques.
• It lowers the detection threshold from 3 keV to 1.1 keV, expanding the fiducial volume and improving background discrimination.
• The analysis achieves a 90% confidence limit of 0.6 zb at 33 GeV/c², setting the most stringent constraints for WIMPs above 4 GeV/c².

Improved Limits on Scattering of Weakly Interacting Massive Particles from Reanalysis of 2013 LUX Data

The presented paper reevaluates the 2013 dataset from the Large Underground Xenon (LUX) experiment, providing enhanced limits on the scattering cross sections of Weakly Interacting Massive Particles (WIMPs). This reassessment is marked by methodological advancements and new calibration techniques which significantly refine the sensitivity to low-mass WIMPs.

The LUX experiment, a dual-phase xenon time-projection chamber (TPC), remains a prominent player in the direct detection of dark matter candidates, specifically WIMPs. The focal point of this paper is the reanalysis of the 1.4×10^4 kg day of exposure data initially reported in 2013. The original analysis set stringent upper limits on the spin-independent WIMP-nucleon cross section by assuming zero efficiency below 3 keV for nuclear recoil events, which limited the sensitivity to low-energy interactions.

Methodological Advancements

Several significant enhancements characterize this updated analysis:

1. Calibration Enhancements: The paper details improved single-photon calibration at the scintillation wavelength and advancements in event-reconstruction algorithms. The background model has been revised to incorporate wall-originated events within an expanded fiducial volume.
2. In Situ Calibration: Utilizing kinematically constrained nuclear recoils and tritium beta decays, the sensitivity threshold has been reduced to 1.1 keV. This marks a notable improvement over the previous 3 keV threshold.
3. Improvements in Background Mitigation: Addressing systematic uncertainties, the analysis incorporates a refined model for backgrounds, especially those emanating from the detector's sidewalls. This refinement allows for a more accurate discrimination against actual WIMP signals.

Results and Implications

The results substantiate more stringent constraints on WIMP interactions with nucleons in the mass range above 4 GeV/c². The analysis reports a 90% confidence limit with a minimum spin-independent cross section of 0.6 zb at a WIMP mass of 33 GeV/c². This represents the most stringent limits in this mass range over previous analyses, affirming that improvements in calorimetric methods and data processing directly enhance dark matter detection sensitivities. The implications for low-mass WIMP searches are particularly noteworthy as they explore a previously uncharted parameter space.

Future Prospects

While the paper primarily elucidates advancements in analysis techniques, it inherently points toward the potential for further developments in the field. Modifications to these methodologies can inform future experiments, such as LUX-ZEPLIN, which aims to enhance detection sensitivity with a larger target mass and improved background suppression techniques.

Ultimately, this reanalysis of the LUX data signifies an essential methodological step in the ongoing search for dark matter. The specific enhancements in detector calibration and data processing techniques are likely to become indispensable in interpreting results as the field pushes toward greater sensitivities in low-mass WIMP detection.