Long-lived Sterile Neutrino Searches at Future Muon Colliders

TL;DR

This paper investigates the potential of future high-energy muon colliders to detect long-lived sterile neutrinos, introducing a model with a new gauge symmetry that enhances production and allows for displaced vertex searches.

Contribution

The study proposes a Dirac sterile neutrino model with ${ m U(1)}_{L_mu-L_ au}$ symmetry and analyzes the collider's sensitivity to sterile neutrino masses and mixing angles.

Findings

Muon colliders can probe sterile neutrino masses up to 5 TeV.

Displaced vertex method effectively detects long-lived neutrinos.

Enhanced production via ${ m U(1)}_{L_mu-L_ au}$ symmetry improves search prospects.

Abstract

We explore the potential of studying sterile neutrinos at a future high-energy muon collider, where these particles can generate small active neutrino masses via the seesaw mechanism and exhibit long-lived particle signatures. A Dirac sterile neutrino model with ${\rm U(1)}_{L_\mu-L_\tau}$ symmetry is introduced, where the heavy right-handed neutrino ($N_R$) produces tiny active neutrino masses, and the light left-handed neutrino ($N_L$) naturally behaves as a long-lived particle. The ${\rm U(1)}_{L_\mu-L_\tau}$ gauge symmetry also enhances sterile neutrino pair production at a future high-energy muon collider. Using the displaced vertex method, the muon collider can search for heavy sterile neutrino, especially for $m_L> m_W$. We find that a muon collider with $\sqrt{s} = 3~ (10)$ TeV and luminosity $L=1~(10)$ ab$^{-1}$ can probe $N_L$ masses of $m_L \in [100,~1500~(5000)]$ GeV and mixing angles $\theta_{\nu L} \in [10^{-13},~10^{-6}]$.