Results from a search for dark matter in the complete LUX exposure

Abstract: We report constraints on spin-independent weakly interacting massive particle (WIMP)-nucleon scattering using a 3.35e4 kg-day exposure of the Large Underground Xenon (LUX) experiment. A dual-phase xenon time projection chamber with 250 kg of active mass is operated at the Sanford Underground Research Facility under Lead, South Dakota (USA). With roughly fourfold improvement in sensitivity for high WIMP masses relative to our previous results, this search yields no evidence of WIMP nuclear recoils. At a WIMP mass of 50 GeV/c^2, WIMP-nucleon spin-independent cross sections above 2.2e-46 cm^2 are excluded at the 90% confidence level. When combined with the previously reported LUX exposure, this exclusion strengthens to 1.1e-46 cm^2 at 50 GeV/c^2.

• The paper demonstrates a significant improvement in sensitivity by excluding WIMP-nucleon cross sections above 2.2×10⁻⁴⁶ cm² at 50 GeV/c² with 90% confidence.
• The paper employs advanced calibration techniques using neutron and tritium sources in a dual-phase xenon TPC to effectively distinguish nuclear from electronic recoils.
• The paper integrates a comprehensive 332 live-day dataset with prior results to robustly narrow the parameter space for supersymmetric dark matter models.

Evaluation of the LUX Experiment's Contradiction to WIMP-Nucleon Scattering

The paper reports on the significant findings obtained from the comprehensive LUX (Large Underground Xenon) experiment aimed at searching for interactions between dark matter constituents, specifically weakly interacting massive particles (WIMPs), and normal matter. This analysis is characterized by a notable depth in experimental technique and thoroughness in observation, offering critical insights into the elusive nature of dark matter.

The LUX experiment, leveraging a dual-phase xenon time projection chamber (TPC), operated with an active mass of 250 kg of liquid xenon at the Sanford Underground Research Facility (SURF). The substantial $3.35 \times 10^4$ kg-day exposure aimed at detecting WIMP-induced nuclear recoils. By following a methodology that effectively discriminates between electronic and nuclear recoils, the experiment significantly enhances sensitivity to potential WIMP interactions.

Noteworthy from the results is the marked improvement in detection sensitivity for high WIMP masses, achieving approximately four times the sensitivity compared to previous results. This advancement allows the setting of more stringent constraints on WIMP-nucleon cross sections. For example, at a WIMP mass of 50 GeV/$c^2$, cross sections exceeding $2.2 \times 10^{-46}$ cm$^2$ have been excluded with 90% confidence. This exclusion tightens to $1.1 \times 10^{-46}$ cm$^2$ upon integrating previous LUX data with the current exposure. These are remarkable numerical limits in the ongoing global search for dark matter.

The methodology applied in this research involved meticulous calibration efforts. These included novel calibrations using neutron sources and tritium decays to accurately reduce background noise and enhance the understanding of detector responses. This technique, coupled with the extensive 332 live-day data collection, inherently bolstered the experimental reliability and the robustness of the results against background interference.

From a theoretical standpoint, the implications are profound. By reinforcing null results at lower cross-section thresholds, the LUX experiment narrows the parameter space for WIMP models, particularly challenging some supersymmetric theories predicting interaction rates. Moreover, the ability to achieve an even stricter limit when combined with previous data suggests a continuous refinement in experimental approaches and technologies.

The practical implications of the LUX results extend into future dark matter research programs and instrumentation design. The methodologies validated here could directly influence next-generation detectors which aim to provide broader coverage and deeper sensitivity.

Looking ahead, the field is likely to focus on further minimizing background interference and increasing detector mass and sensitivity. Such advances may eventually lead to a detection or provide more restrictive constraints on WIMP-nucleon interactions, progressively closing the gap on one of modern physics' enduring questions: the true nature of dark matter.

In conclusion, the study is a substantive contribution to particle astrophysics, underscoring the continual refinement of experimental strategies in the search for dark matter. It serves both as a remarkable technical achievement in terms of what was measured and an essential stepping stone for future inquiries into cosmic dark matter.