Parametrizing the Nuclear Recoil Variance of Cryogenic Dark Matter Detectors

Understanding the quenching of the ionization signal from nuclear recoil (NR) events relative to that of electron recoils has significant implications for direct-detection dark-matter-search experiments. Significant attention has been devoted to measuring the quenching factor down to low recoil energy. A relatively unexplored area is the NR variance of the response which directly affects the expected signal shape from weakly interacting massive particle (WIMP) scatters in a detector. Previous work has suggested that the NR variance is higher than expected. This presentation describes parameterizing the variance in SuperCDMS Soudan data including application of a Markov Chain Monte Carlo analysis to quantify parameter uncertainties.