Abstract
Recent measurements of the germanium quenching factor deviate significantly from the predictions of the standard Lindhard model for nuclear recoil energies below a keV. This departure may be explained by the Migdal effect in neutron scattering on germanium. We show that the Migdal effect on the quenching factor can mimic the signal of a light Z' or light scalar mediator in coherent elastic neutrino nucleus scattering experiments with reactor antineutrinos. It is imperative that the quenching factor of nuclei with low recoil energy thresholds be precisely measured close to threshold to avoid such confusion. This will also help in experimental searches of light dark matter.
Highlights
Coherent elastic neutrino-nucleus scattering ðCEνNSÞ is a standard model (SM) process in which low-energy neutrinos scatter off the atomic nucleus as a whole via the neutral-current of SM weak interactions [1]
We compare the spectra of two scenarios: (i) the light Z0 or scalar mediator with the standard Lindhard model for the quenching factor; (ii) the SM with the Migdal effect on the quenching factor parametrized by Migdal parameters
We find that the Migdal effect on the quenching factor can be mimicked by a light
Summary
Coherent elastic neutrino-nucleus scattering ðCEνNSÞ is a standard model (SM) process in which low-energy neutrinos scatter off the atomic nucleus as a whole via the neutral-current of SM weak interactions [1]. CEνNS was first observed by the COHERENT experiment in 2017 with a cesium-iodide (CsI) detector using neutrinos produced by stopped pion decay at the Spallation Neutron Source at the Oak Ridge National Laboratory [2]. The observation of CEνNS opens a new window to probe new physics beyond the SM at low energies [3]. CEνNS has been measured in an argon detector by the COHERENT collaboration at more than 3σ significance [4]. The CONNIE [5] and CONUS [6] experiments have constrained CEνNS with reactor antineutrinos in a silicon and germanium detector, respectively. More data from the CEνNS experiments will enable a precision test of the SM at the low energy frontier
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