# Probing nonstandard lepton number violating interactions in neutrino oscillations

## TL;DR

This paper investigates nonstandard lepton number violating interactions in neutrino oscillations, deriving probabilities, comparing with standard models, and setting experimental bounds to enhance understanding of neutrino properties.

## Contribution

It introduces new expressions for lepton number violating oscillation probabilities and analyzes experimental bounds on these interactions within the effective field theory framework.

## Key findings

- Non-standard interactions can alleviate mass suppression in LNV processes.
- Bounds from MINOS and KamLAND constrain interaction strengths.
- Comparison with neutrinoless double beta decay limits the parameter space.

## Abstract

We discuss lepton number violating processes in the context of long-baseline neutrino oscillations. We summarise and compare neutrino flavour oscillations in quantum mechanics and quantum field theory, both for standard oscillations and for those that violate lepton number. When the active neutrinos are Majorana in nature, the required helicity reversal gives a strong suppression by the neutrino mass over the energy, $(m_{\nu}/E_{\nu})^{2}$. Instead, the presence of non-standard lepton number violating interactions incorporating right-handed lepton currents at production or detection alleviate the mass suppression while also factorising the oscillation probability from the total rate. Such interactions arise from dimension-six operators in the low energy effective field theory of the Standard Model. We derive general and simplified expressions for the lepton number violating oscillation probabilities and use limits from MINOS and KamLAND to place bounds on the interaction strength in interplay with the unknown Majorana phases in neutrino mixing. We compare the bounds with those from neutrinoless double beta decay and other microscopic lepton number violating processes and outline the requirements for future short- and long-baseline neutrino oscillation experiments to improve on the existing bounds.