Abstract
Sterile neutrinos with keV-MeV masses and non-zero transition magnetic moments can be probed through low-energy nuclear or electron recoil measurements. Here we determine the sensitivities of current and future searches, showing how they can probe a previously unexplored parameter region. Future coherent elastic neutrino-nucleus scattering (CEνNS) or elastic neutrino-electron scattering (EνES) experiments using a monochromatic 51Cr source can fully probe the region indicated by the recent XENON1T excess.
Highlights
Solar neutrino data from the KamLAND experiment, one gets constraints on the Majorana neutrino transition magnetic moments (TMMs) and solar magnetic fields [21, 22]
Neutrino experiments looking for coherent elastic neutrino-nucleus scattering (CEνNS) or elastic neutrino-electron scattering (EνES) events have been proven to be a valuable tool for investigating neutrino oscillations beyond the standard three-neutrino picture, such as deviations from lepton unitarity [29,30,31], or the presence of light sterile neutrinos [32]
The recent XENON1T excess is shown in the top left panel of figure 1, where we present our results assuming the case of a νμ with the indicated benchmark value of effective neutrino magnetic moment and sterile neutrino mass
Summary
For the case of Majorana particles, the electromagnetic interaction Hamiltonian in the mass basis is given by [16]. For short-baseline experiments, and assuming very small mixing between active and sterile states, one can just assume at detectors the presence of pure νe and νμ beams In this case, the full analytical expressions for the effective neutrino magnetic moments for νe and νμ in the mass basis are lengthy. For the case of νμ → νs or νμ → νs transitions, we get μM νμ→νs 2 = |λ14|2 c224 sin 2θ12s13c23s23 cos δ + s212c223 + c212s213s223 + c12c13s14 sin 2θ24 [s12c23 cos δ14 + c12s13s23 cos (δ − δ14)] + s224 c212c213s214 + c214 + |λ24|2 c224 − sin 2θ12s13c23s23 cos δ + c212c223 + s212s213s223. Assuming a small active-sterile neutrino mixing, sin θi4 ≤ 0.01, the last two expressions simplify considerably and read μM νe→νs μM νμ→νs. As shown in ref. [44], for the case of n Majorana neutrinos the number of physical phases is n(n − 2), we have in general 8 physical phases expected in the present study (see tables 1 and 2)
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