Lepton-Number-Charged Scalars and Neutrino Beamstrahlung

TL;DR

This paper investigates the theoretical implications and experimental signatures of lepton-number-charged scalars (LeNCS) that couple to neutrinos, potentially detectable through neutrino beamstrahlung in current and future experiments.

Contribution

It introduces the concept of LeNCS with specific $B-L$ charge, explores their interactions, and discusses how neutrino experiments can search for these new particles.

Findings

LeNCS can be produced in neutrino experiments via beamstrahlung.

Existing constraints limit LeNCS properties but allow detectable signals.

Future experiments like DUNE could observe LeNCS signatures.

Abstract

Experimentally, baryon number minus lepton number, $B-L$, appears to be a good global symmetry of nature. We explore the consequences of the existence of gauge-singlet scalar fields charged under $B-L$ -- dubbed lepton-number-charged scalars, LeNCS -- and postulate that these couple to the standard model degrees of freedom in such a way that $B-L$ is conserved even at the non-renormalizable level. In this framework, neutrinos are Dirac fermions. Including only the lowest mass-dimension effective operators, some of the LeNCS couple predominantly to neutrinos and may be produced in terrestrial neutrino experiments. We examine several existing constraints from particle physics, astrophysics, and cosmology to the existence of a LeNCS carrying $B-L$ charge equal to two, and discuss the emission of LeNCS's via "neutrino beamstrahlung," which occurs every once in a while when neutrinos scatter off of ordinary matter. We identify regions of the parameter space where existing and future neutrino experiments, including the Deep Underground Neutrino Experiment, are at the frontier of searches for such new phenomena.