A search for light dark matter in XENON10 data (1104.3088v4)

Abstract: We report results of a search for light (<10 GeV) particle dark matter with the XENON10 detector. The event trigger was sensitive to a single electron, with the analysis threshold of 5 electrons corresponding to 1.4 keV nuclear recoil energy. Considering spin-independent dark matter-nucleon scattering, we exclude cross sections \sigma_n>3.5x10^{-42} cm^2, for a dark matter particle mass m_{\chi}=8 GeV. We find that our data strongly constrain recent elastic dark matter interpretations of excess low-energy events observed by CoGeNT and CRESST-II, as well as the DAMA annual modulation signal.

• The paper demonstrates that using the S2 signal in XENON10 lowers the energy threshold to 1.4 keV, enhancing sensitivity to dark matter below 10 GeV.
• It constrains spin-independent scattering cross-sections above 7×10⁻⁴² cm² at 7 GeV, challenging earlier results from CoGeNT, CRESST-II, and DAMA.
• The innovative methodology paves the way for future liquid xenon detectors with improved electron extraction and lower energy detection capabilities.

Analysis of Light Dark Matter Search in XENON10 Data

The paper presents an analysis of the XENON10 experiment's capability to detect light dark matter particles, specifically those with masses less than 10 GeV. The XENON10 detector, a liquid xenon time-projection chamber (TPC), was primarily designed to identify dark matter particles via nuclear recoils. The focus of this paper is the examination of the light dark matter candidate particles through the unique use of the S2 (electron) signal, enabling a lower energy detection threshold.

The research emphasizes a sensitivity to spin-independent (SI) scattering cross-sections on the order of $\sigma_n>7\times10^{-42}$ cm$^2$ for a particle mass $m_\chi=7$ GeV, achieved by leveraging the XENON10 detector to observe very low-energy nuclear recoil events. The innovative approach of utilizing the electron signal provided by the detector expands the range of detectable dark matter interactions, while previously, the primary focus was on scintillation light (S1).

Key Methodological Innovations

The methodology distinguishes itself by enhancing the sensitivity to lighter dark matter particles. This is accomplished by:

• Lower Energy Threshold: The analysis successfully reduces the energy threshold to approximately 1.4 keV, down from the 5 keV threshold used in previous XENON10 analyses. This lower threshold is achieved by relying on the S2 signal which, in this experiment, required a minimum of five electrons.
• Single-Electron Sensitivity: The setup was sensitive to events as minimal as a single electron, exploiting robust S2 signals, allowing for considerable improvement of energy resolution concerning lower-mass dark matter candidates.

Exclusion Limits and Interpretation

The experiment effectively constrains a variety of theoretical models which posit that light dark matter causes low-energy excesses observed in other dark matter experiments, such as CoGeNT and CRESST-II, and notably contradicts the results from DAMA's annual modulation signal. The data analysis used robust statistical methods to extend the parameter space for $m_\chi$ and $\sigma_n$, eliminating cross-section interpretations suggested by these prior results.

Implications and Future Prospects

The findings contribute significantly to the ongoing discourse in astrophysical and particle physics regarding dark matter properties. From a practical point of view, the experiment showcases the capability of liquid xenon TPCs to explore the low-mass regime of dark matter searches, paving the way for upcoming experiments with similar technology, potentially improved in size and electron extraction efficiency.

Theoretical implications of these results suggest a reassessment of light dark matter models, especially those proposing interpretations based on existing low-energy signals in other experiments. As a speculative note, further research can try to enhance discrimination abilities, potentially calking up the aforementioned sensitivity limitations, which could make such setups even more viable for future dark matter exploration endeavors.

In conclusion, the paper effectively demonstrates the utility of using an electron signal-based approach in a liquid xenon detector for probing the elusive region of light dark matter, while articulating a strong exclusion profile against certain claims of its detection through alternative experimental setups. Future developments might focus on refining electron yield models and enhancing background rejection to further increase sensitivity and accuracy in detecting potential dark matter interactions.