Resonances in $\bar\nu_e-e^-$ scattering below a TeV

Abstract

We consider the resonant production and detection of charged mesons in existing and near-future neutrino scattering experiments with $E_\nu \lesssim 1$ TeV, characteristic of high-energy atmospheric neutrinos or collider-sourced neutrino beams. The most promising candidate is the reaction $\bar{\nu}_e e^-\rightarrow \rho^-\rightarrow \pi^- \pi^0$. We discuss detection prospects at FASER$\nu$, the LHC's forward physics facility with nuclear emulsion (FASER$\nu$2) and liquid argon detectors (FLArE) and estimate the number of expected resonance-mediated events in the existing data set of IceCube. We also outline possible detection strategies for the different experimental environments. We predict dozens of events at the forward physics facility and identify cuts with order one signal efficiency that could potentially suppress backgrounds at FASER$\nu$, yielding a signal-to-background ratio larger than 1. Antineutrino-induced $s$-channel meson resonances are yet unobserved Standard Model scattering processes which offer a realistic target for near-term experiments.