Measurement of ER Fluctuations in Liquid Xenon with the LUX Detector Using a Tritium Calibration Source

The LUX WIMP search limit was aided by an internal tritium source resulting in an unprecedented calibration and understanding of the electronic recoil background. The source allows for a check of energy scale calibration and the extraction of fundamental properties of electron recoils in liquid xenon. Recombination probability and its fluctuation have been measured from 1 to 1000 keV, using betas from tritium and Compton scatters from an external $^{137}$Cs source.