Search for neutrinos from annihilation of captured low-mass dark matter particles in the Sun by Super-Kamiokande (1503.04858v1)

Abstract: Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/$c^2$ $\sim$ 200-GeV/$c^2$) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent (SD) WIMP-proton cross section for WIMP masses below 200 GeV/$c^2$ (at 10 GeV/$c^2$, 1.49$\times 10^{-39}$ cm$^2$ for $\chi\chi\rightarrow b \bar{b}$ and 1.31$\times 10^{-40}$ cm$^2$ for $\chi\chi\rightarrow\tau^+\tau^-$ annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent (SI) coupling in the few-GeV/$c^2$ mass range.

• The paper presents a comprehensive search for neutrino signals from low-mass dark matter annihilations in the Sun using 3903 days of Super-Kamiokande data.
• It employs detailed Monte Carlo simulations with WimpSim 3.01 and a least-squares fit to rigorously compare observed neutrino events against modeled expectations.
• The study establishes stringent upper limits on spin-dependent WIMP-proton cross sections, thereby significantly narrowing the parameter space for dark matter models.

Analysis of Neutrino Detection from Low-Mass Dark Matter Annihilations in the Sun via Super-Kamiokande

The Super-Kamiokande collaboration has undertaken a comprehensive investigation into the potential detection of neutrinos originating from the annihilation of weakly interacting massive particles (WIMPs) within the Sun. This work is specifically oriented towards identifying low-mass dark matter particles by scrutinizing neutrino signals produced through such annihilation events. Leveraging Super-Kamiokande's capabilities, this analysis integrates neutrino events within the detector's interaction vertices in addition to upward-going muon events produced in the surrounding rock, a methodological expansion from previous studies.

Methodological Framework

The Super-Kamiokande detector, a large water Cherenkov detector located in the Kamioka mine, Japan, provides an extensive platform for capturing high-energy neutrino data. This research utilizes 3903 days of data from the SK I-IV run periods, across various neutrino event categories, including Fully-Contained (FC), Partially-Contained (PC), and upward-going muon (up-$\mu$) events. These events are categorized based on energy and containment parameters, enhancing the potential detection of signals from WIMP interactions at masses ranging 4 GeV/$c^2$ to 200 GeV/$c^2$.

Analytical Approach

To account for the anticipated neutrino flux from WIMP interactions, the paper implements a meticulous Monte Carlo simulation strategy, particularly employing the WimpSim 3.01 to model neutrino fluxes from WIMP annihilation. Furthermore, the analysis constructs a least-squares fit to rigorously compare observed data to modeled expectations, incorporating a comprehensive range of systematic uncertainties spanning neutrino interactions, event detection, and atmospheric neutrino backgrounds.

Key Findings

The paper reports no discernible excess of neutrino signals above expected background levels, allowing for the derivation of upper limits on WIMP-nucleon elastic scattering cross sections. Notably, this research establishes some of the most stringent constraints on the spin-dependent WIMP-proton cross section for masses below 200 GeV/$c^2$. Specifically, the limits of 1.49×10⁻³⁹ cm² for the $b\overline{b}$ annihilation channel and 1.31×10⁻⁴⁰ cm² for the $\tau^+\tau^-$ channel for WIMP masses around 10 GeV/$c^2$ are presented as current upper benchmarks.

Implications and Future Considerations

The constraints provided by this paper enhance our understanding of WIMP properties, effectively narrowing the parameter space for low-mass dark matter detection. The focus on examining additional particle types and further refining the methods for interpreting neutrino data from terrestrial detectors marks a substantial contribution to ongoing dark matter research. Future endeavors could involve enhancements in detector sensitivity, cross-sectional models, and integration with multi-observational platforms.

The theoretical implications of these findings bolster the astrophysical models relating to dark matter density distribution and potential particle candidates within reach of detection. Continued interdisciplinary efforts and technological advancements will be necessary to extend these findings and further explore WIMP interactions in cosmological and local environments. The approach employed in this analysis may also be adapted to future projects seeking to deepen our understanding of dark matter and its elusive properties.