Longer-Lived Mediators from Charged Mesons and Photons at Neutrino Experiments

TL;DR

This paper investigates the potential of neutrino experiments to detect longer-lived mediators, such as scalars produced from meson decays and photons, which could explain anomalies like the muon g-2 discrepancy.

Contribution

It evaluates the sensitivity of current and upcoming neutrino experiments to flavor-specific scalar mediators, highlighting their ability to explore new parameter spaces.

Findings

Charged meson decays enhance scalar production, especially muonphilic scalars.

Neutrino experiments can probe unexplored regions relevant to muon g-2.

Bethe-Heitler scattering can detect flavor-specific leptonic final states.

Abstract

Since many of the dark-sector particles interact with Standard Model (SM) particles in multiple ways, they can appear in experimental facilities where SM particles appear in abundance. In this study, we explore a particular class of longer-lived mediators that are produced from photons, charged mesons, neutral mesons, and $e^\pm$ that arise in proton-beam fixed-target-type neutrino experiments. This class of mediators encompasses light scalars that appear in theories like extended Higgs sectors, muon(electro)philic scalars, etc. We evaluate the sensitivities of these mediators at beam-based neutrino experiments such as the finished ArgoNeuT, ongoing MicroBooNE, SBND, ICARUS, and the upcoming DUNE experiment. We realize that scalars are more enhanced while produced from three-body decay of charged mesons, especially if they are muonphilic in nature. For scenarios that contain muonphilic scalars, these experiments can probe unexplored regions of parameter space that can explain the current discrepancy in the anomalous magnetic moment of muons. The sensitivity of electrophilic scalars at the DUNE Near Detector can explore new regions. We also show that Bethe-Heitler scattering processes can be used to probe flavor-specific lepton final states even for the mediator masses below twice the lepton mass.