Neutrino Trident Scattering at Near Detectors

TL;DR

This paper provides a comprehensive calculation of neutrino trident scattering cross sections, clarifies the limitations of the Equivalent Photon Approximation, and estimates event rates at various near detectors, enhancing the understanding of this rare Standard Model process.

Contribution

It offers the first complete four-body phase space calculation for neutrino trident production across different targets, addressing previous inconsistencies and refining cross section estimates.

Findings

The Equivalent Photon Approximation is only valid for dimuon coherent scattering.

Complete phase space calculations improve cross section accuracy.

Many near detectors can feasibly measure neutrino trident events.

Abstract

Neutrino trident scattering is a rare Standard Model process where a charged-lepton pair is produced in neutrino-nucleus scattering. To date, only the dimuon final-state has been observed, with around 100 total events, while the other channels are as yet unexplored. In this work, we compute the trident production cross section by performing a complete four-body phase space calculation for different hadronic targets. This provides a correct estimate both of the coherent and the diffractive contributions to these cross sections, but also allows us to address certain inconsistencies in the literature related to the use of the Equivalent Photon Approximation in this context. We show that this approximation can give a reasonable estimate only for the production of dimuon final-states in coherent scattering, being inadmissible for all other cases considered. We provide estimates of the number and distribution of trident events at several current and future near detector facilities subjected to intense neutrino beams from accelerators: five liquid-argon detectors (SBND, $\mu$BooNE, ICARUS, DUNE and $\nu$STORM), the iron detector of T2K (INGRID) and three detectors made of composite material (MINOS, NO$\nu$A and MINER$\nu$A). We find that for many experiments, trident measurements are an attainable goal and a valuable addition to their near detector physics programme.