New limits on spin-independent and spin-dependent couplings of low-mass WIMP dark matter with a germanium detector at a threshold of 220 eV

Understand

An energy threshold of (220+-10) eV was achieved at an efficiency of 50% with a four-channel ultra-low-energy germanium detector each with an active mass of 5 g.

• This provides a unique probe to WIMP dark matter with mass below 10 GeV.
• With a data acquisition live time of 0.338 kg-day at the Kuo-Sheng Laboratory, constraints on WIMPs in the galactic halo were derived.
• The limits improve over previous results on both the spin-independent WIMP-nucleon and the spin-dependent WIMP-neutron cross-sections for WIMP mass between 3-6 GeV.