The scintillation efficiency of carbon and hydrogen recoils in an organic liquid scintillator for dark matter searches

Dark matter candidates such as the weakly interacting massive particles can be detected through elastic scatterings with a nucleus. The scintillation efficiency of carbon and hydrogen nuclear recoils in an organic liquid scintillator was measured for such a possible dark matter detector. The recoil energies from 50 keV to ∼1 MeV were explored for both nuclei. The carbon recoil efficiency, of particular interest for a dark matter detector, was observed to increase from 0.8+0.09−0.11% of the electron recoil efficiency at 500 keV to 4.8+0.85−2.99% at 46 keV. Such an enhancement is very encouraging for the purpose of dark matter searches as well as other similar low-energy experiments, and the results are well described by a modified Birksʹ light yield formula.