Heavy Neutral Leptons at the Electron-Ion Collider

TL;DR

The paper explores the potential of the Electron-Ion Collider to detect heavy neutral leptons across a broad mass range, offering new insights into physics beyond the Standard Model and neutrino mass mechanisms.

Contribution

It provides the first detailed analysis of EIC's sensitivity to HNLs, including prompt, displaced, and invisible decay modes, across a wide mass and mixing angle spectrum.

Findings

EIC can probe HNL masses from 1 to 100 GeV.

Sensitivity to mixing angles as low as 10^{-6} for displaced decays.

Complementary to other experimental searches for HNLs.

Abstract

The future Electron-Ion Collider (EIC) at Brookhaven National Laboratory, along with its primary capacity to elucidate the nuclear structure, will offer new opportunities to probe physics beyond the Standard Model coupled to the electroweak sector. Among the best motivated examples of such new physics are new heavy neutral leptons (HNLs), which are likely to play a key role in neutrino mass generation and lepton number violation. We study the capability of the EIC to search for HNLs, which can be produced in electron-proton collisions through charged current interactions as a consequence of their mixing with light neutrinos. We find that, with the EIC design energy and integrated luminosity, one is able to probe HNLs in the mass range of 1 GeV$-100$ GeV with mixing angles down to the order of $10^{-4} - 10^{-3}$ through the prompt decay, and $10^{-6} - 10^{-4}$ via the displaced decay signatures. We also consider the invisible mode where an HNL is undetected or decaying to dark sector particles. One could potentially probe heavy HNLs for mixing angles in the window $10^{-3}-10^{-2}$, provided SM background systematics can be brought under control. These searches are complementary to other probes of HNLs, such as neutrino-less double-$\beta$ decay, meson decay, fixed-target, and high-energy collider experiments.