Mass Reconstruction of Heavy Neutral Leptons from Stopped Mesons

TL;DR

This paper demonstrates that the ICARUS LArTPC detector can reconstruct the mass of heavy neutral leptons produced in stopped meson decays, enabling exploration of new parameter space in the 70-190 MeV range.

Contribution

It introduces a robust mass reconstruction method for HNLs using two-body kinematics and detector resolution, applicable to current and future LArTPC experiments.

Findings

ICARUS can reconstruct HNL mass in 70-190 MeV range.

The method is robust under realistic detector resolutions.

Potential synergy with DUNE and PIP-II to probe HNLs.

Abstract

Heavy neutral leptons (HNLs), depending on their mass and mixing, can be efficiently produced in meson decays from the target or absorber in short- to medium-baseline accelerator neutrino experiments, leaving detectable signals through their decays inside the neutrino detectors. We show that the currently running ICARUS experiment at Fermilab can reconstruct the HNL mass and explore new HNL parameter space in the mass range of 70-190 MeV. The mass reconstruction is enabled by two ingredients: (i) simple two-body kinematics of HNL production from stopped kaon decays at the NuMI absorber, followed by HNL decay into a charged-lepton pair and neutrino at the detector, and (ii) high resolution of Liquid Argon Time Projection Chamber (LArTPC) detectors in reconstructing final state particles. Our mass reconstruction method is robust under realistic energy resolution and angular smearing of the charged leptons, and is applicable to any LArTPC detector. We also discuss the synergy between ICARUS and future facilities like DUNE near detector and PIP-II beam dump in probing the HNL parameter space.