Abstract

Searches for neutrino magnetic moments/transitions in low energy neutrino scattering experiments are sensitive to effective couplings, which are an intricate function of the Hamiltonian parameters. We study the parameter space dependence of these couplings in the Majorana (transitions) and Dirac (moments) cases, as well as the impact of the current most stringent experimental upper limits on the fundamental parameters. In the Majorana case we find that for reactor, short-baseline, and solar neutrinos, $CP$ violation can be understood as a measurement of parameter space vectors misalignments. The presence of nonvanishing $CP$ phases opens a blind spot region where---regardless of how large the parameters are---no signal can be observed in either reactor or short-baseline experiments. Identification of these regions requires a combination of different datasets and allows for the determination of those $CP$ phases. We point out that stringent bounds not necessarily imply suppressed Hamiltonian couplings, thus allowing for regions where disparate upper limits can be simultaneously satisfied. In contrast, in the Dirac case stringent experimental upper limits necessarily translate into tight bounds on the fundamental couplings. In terms of parameter space vectors, we provide a straightforward mapping of experimental information into parameter space.

Highlights

  • Experimental signals of magnetic and electric dipole moments have been searched for in a large variety of environments

  • Searches for neutrino magnetic moments/transitions in low energy neutrino scattering experiments are sensitive to effective couplings, which are an intricate function of the Hamiltonian parameters

  • In the Majorana case we find that for reactor, short-baseline, and solar neutrinos, CP violation can be understood as a measurement of parameter space vectors misalignments

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Summary

INTRODUCTION

Experimental signals of magnetic and electric dipole moments have been searched for in a large variety of environments (for a review see Ref. [1]). The presence of these interactions may have deep implications for DM direct detection searches [34] Motivated by these experiments, in this paper we study the implications of measurements (or upper bounds, resulting from the absence of a signal) of neutrino magnetic and electric dipole moments/transitions [35,36,37,38,39,40] on parameter. In the Appendixes A and B we calculate the phase average for solar neutrinos and demonstrate the connection between blind spots and the unitarity of the lepton mixing matrix for the Majorana case

NEUTRINO MAGNETIC AND ELECTRIC DIPOLE MOMENT INTERACTIONS
C Hermitian Hermitian
SCATTERING PROCESSES INDUCED BY MAGNETIC AND ELECTRIC DIPOLE MOMENTS
10 MeV L eV2
Effective couplings in reactor and short baseline accelerator experiments
Effective couplings in solar neutrino experiments
DIRAC NEUTRINO MAGNETIC AND ELECTRIC DIPOLE MOMENTS
CONCLUSIONS
Methods
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