Novel signatures of heavy neutral lepton at muon collider

A

bstract

The Higgs-strahlung process ℓ ⁺ ℓ ⁻ → Zh is one of the most important production channels of the standard model Higgs boson h at the lepton colliders. The cross section reaches the maximum value slightly above the threshold

, and decreases as ∼ 1/ s at high energies. In the gauged extension models, the new gauge boson Z ^′ and heavy Higgs boson H exist after the symmetry breaking. The heavy Higgs-strahlung process ℓ ⁺ ℓ ⁻ → Z ^′ H would also reach the maximum cross section around the threshold

$$ \sqrt{s}\sim {m}_{Z^{\prime }}+{m}_H $$ s ~ m Z ′ + m H

. Therefore, the future high energy lepton colliders, such as the TeV scale muon collider, are promising to probe this new process. If heavy neutral lepton N is introduced to generate the tiny neutrino masses via seesaw mechanism, novel signatures could arise from μ ⁺ μ ⁻ → Z ^′ H → NN + NN → 4 μ ^± +4 J and μ ⁺ μ ⁻ → Z ^′ H → μ ⁺ μ ⁻ + NN → μ ^± + μ ^∓ + 2 J , where the fat-jets J come from the hadronic decay of W bosons. In this paper, we investigate the same-sign tetralepton signature 4 μ ^± + 4 J and the same-sign trilepton signature 3 μ ^± + μ ^∓ + 2 J at the 3 TeV and 10 TeV muon collider.