Response of CsI[Na] to Nuclear Recoils: Impact on Coherent Elastic Neutrino-Nucleus Scattering (CE$ν$NS)

Authors:
  • JCJ. I. Collar
    J. I. Collar
  • AKA. R. L. Kavner
    A. R. L. Kavner
  • CLC. M. Lewis
    C. M. Lewis
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Abstract
A new measurement of the quenching factor for low-energy nuclear recoils in CsI[Na] is presented. Past measurements are revisited, identifying and correcting several systematic effects. The resulting global data are well-described by a physics-based model for the generation of scintillation by ions in this material, in agreement with phenomenological considerations. The uncertainty in the new model is reduced by a factor of four with respect to an energy-independent quenching factor initially adopted as a compromise by the COHERENT collaboration. A significantly improved agreement with Standard Model predictions for the first measurement of CE$\nu$NS is generated. We emphasize the critical impact of the quenching factor on the search for new physics via CE$\nu$NS experiments.