Search for Boosted Dark Matter Interacting with Electrons in Super-Kamiokande

A search for boosted dark matter using 161.9 kt yr of Super-Kamiokande IV data is presented. We search for an excess of elastically scattered electrons above the atmospheric neutrino background, with a visible energy between 100 MeV and 1 TeV, pointing back to the Galactic center or the Sun. No such excess is observed. Limits on boosted dark matter event rates in multiple angular cones around the Galactic center and Sun are calculated. Limits are also calculated for a baseline model of boosted dark matter produced from cold dark matter annihilation or decay. This is the first experimental search for boosted dark matter from the Galactic center or the Sun interacting in a terrestrial detector.

Figure 1

Signal efficiency of the FCFV selection and analysis cuts as a function of the energy. Beginning with the FCFV selection (dashed-dotted blue curve), the addition of the one-ring (for $E_{\mathrm{vis}}<100\mathrm{GeV}$, dashed green curve), $e$-like (dotted red curve), and finally zero decay electrons and zero tagged neutrons cuts to arrive at the final efficiency (solid cyan curve) are shown. The efficiency of the zero decay electrons cut is $>99.99\%$, so that the drop from the dotted red line to the solid cyan line is due solely to the neutron tagging cut.

Figure 2

Neutron tagging cut systematic error estimation. Data and MC fits are to logarithmic function.

Figure 3

90% confidence interval upper limits for $m_B=200\mathrm{MeV}$, $m_{\gamma }^{\prime }=20\mathrm{MeV}$, and $g^{\prime }=0.5$, for boosted dark matter produced by annihilation (top) and decay (bottom).