Measurements of the angular distribution of light reflected off PTFE in liquid xenon

IBEX is an experiment designed to measure the angular distribution of light reflected off of polytetrafluoroethylene (PTFE) submerged in liquid xenon, in order to investigate microphysical models of reflection in this context. This is valuable information for experiments employing PTFE in liquid xenon time projection chambers, such as the LUX-ZEPLIN dark matter direct detection experiment. Such detectors rely on the poorly understood high total reflectance of PTFE to xenon scintillation light to achieve excellent light collection efficiency. Since the energy thresholds of such experiments are strongly dependent on the light collection efficiency, a model of the reflectance behavior is desired. Furthermore, IBEX can be used to inform a more accurate simulation of the distribution of light in such detectors. We present the results of IBEX, including a discussion of the dependence on xenon temperature and pressure, the wavelength of light, the type of PTFE, and the surface finish of the sample.