Detectability of Light Dark Matter with Superfluid Helium.
We show that a two-excitation process in superfluid helium, combined with sensitivity to meV energy depositions, can probe dark matter down to the ∼keV warm dark matter mass limit. This mass reach is 3 orders of magnitude below what can be probed with ordinary nuclear recoils in helium at the same energy resolution. For dark matter lighter than ∼100  keV, the kinematics of the process requires the two athermal excitations to have nearly equal and opposite momentum, potentially providing a built-in coincidence mechanism for controlling backgrounds.
Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Berkeley Center for Theoretical Physics, University of California, Berkeley, California 94720, USA.
Katelin
K
Schutz
Theoretical Physics Group, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA and Berkeley Center for Theoretical Physics, University of California, Berkeley, California 94720, USA.
Kathryn M
KM
Zurek