Alpha quenching in liquid scintillator neutrino detectors

Liquid scintillator has been widely used in neutrino detectors. Understanding its energy response is critical for the success of current and future neutrino observatories like SNO+, JUNO, Theia, etc. Conventional modeling of alpha particle signals in liquid scintillator is based on the Birks' law, which uses a single Birks' constant to describe the quenching of scintillation light from alpha particles. Here we present a study with the SNO+ scintillator phase data using an energy-dependent Birks' parameterization to improve the model. The uranium and thorium decay chains have multiple alphas with quenched energies ranging from ~ 0.4 to ~ 1.2 MeV, providing a range of energies to fit with the improved model.