Fat Jet Signature of a Heavy Neutrino at Lepton Collider

TL;DR

This paper investigates the potential to discover very heavy neutrinos at future electron-positron colliders, utilizing fat-jet signatures from boosted decay products, and demonstrates significant sensitivity improvements over the LHC.

Contribution

It introduces a detailed analysis of heavy neutrino detection via fat-jet signatures at $e^+e^-$ colliders, including both cut-based and multivariate methods, for masses up to 2700 GeV.

Findings

Heavy neutrinos with masses 600-2700 GeV can be detected at 5σ significance.

Sensitivity at $e^+e^-$ colliders exceeds that of the LHC by an order of magnitude.

The analysis employs boosted fat-jet techniques and advanced multivariate analysis methods.

Abstract

We explore the discovery prospect of a very heavy neutrino at the proposed $e^+e^-$ collider for two different c.m.energies $\sqrt{s}=1.4$ TeV and 3 TeV. We consider production of heavy neutrino via $s$ and $t$-channel processes, and its subsequent prompt decays leading to semi-leptonic final states, along with significant missing energy. For our choice of masses, the gauge boson produced from heavy neutrino decay is highly boosted, leading to a fat-jet. We carry out a detail signal and background analysis for $e^{\pm}+j_{\rm{fat}}+\cancel{E}_{T}$ final state using both cut based and multivariate techniques. We show that a heavy neutrino of mass $600-2700$ GeV and active-sterile mixing $|V_{eN}|^2 \sim 10^{-5}$ can be probed with $5\sigma$ significance at $e^{+}e^{-}$ collider after collecting $\mathcal{L}=500$ $\rm{fb}^{-1}$ of data. We find the sensitivity reach at $e^{+}e^{-}$ collider is order of magnitude enhanced as compared to LHC.