Scintillation yield from electronic and nuclear recoils in superfluid <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>He</mml:mi></mml:mrow><mml:mprescripts /><mml:none /><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>

Superfluid He4 is a promising target material for direct detection of light (<1 GeV) dark matter. Possible signal channels available readout in this medium include prompt photons, triplet excimers, and roton phonon quasiparticles. The relative yield these signals has implications the sensitivity discrimination power superfluid matter detector. Using 16 cm3 volume 1.75 K read out by six immersed photomultiplier tubes, we measured scintillation from electronic recoils ranging between 36.3 185 keVee, yielding mean size 1.25−0.03+0.03 phe/keVee, nuclear 53.2 to 1090 keVnr. We compare results our measurements an existing semiempirical model based on helium-helium electron-helium interaction cross sections. also study behavior delayed components as function recoil type energy, further avenue He4.12 MoreReceived 5 August 2021Accepted 21 March 2022DOI:https://doi.org/10.1103/PhysRevD.105.092005© 2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDark matterParticle astrophysicsParticle matterTechniquesDark detectorsNeutrino detectorsScintillatorsParticles & FieldsGravitation, Cosmology Astrophysics