Long-lived Sterile Neutrino Searches at Future Muon Colliders

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 ${\mathrm{U}(1)}_{L_{\mu }-L_{\tau }}$ 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 ${\mathrm{U}(1)}_{L_{\mu }-L_{\tau }}$ 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 ${\theta }_{\nu L}\in [10^{-13},10^{-6}]$.

Comments: 22 pages, 6 figures