Measurement of the scintillation resolution in liquid xenon and its impact for future segmented calorimeters

We report on a new measurement of the energy resolution that can be attained in liquid xenon when recording only the scintillation light. Our setup is optimized to maximize light collection, and uses state-of-the-art, high-PDE, VUV-sensitive silicon photomultipliers. We find a value of 3.7 $\pm$ 0.4% at 511 keV, once saturation effects are corrected for, a result close to the Poissonian resolution that we expect in our setup (2.8 $\pm$ 0.4% $\sigma$ at 511 keV). Our results in the intrinsic resolution (2.3 $\pm$ 0.8 %) are compatible, within errors, at 511 keV, with those found by theoretical estimations which have been standing for the last twenty years, 1.8%. Our work opens new possibilities for apparatus based on liquid xenon and using scintillation only. In particular it suggests that modular scintillation detectors using liquid xenon can be very competitive as building blocks in segmented calorimeters, with applications to Positron Emission Tomography technology.