Displaced vertex signatures of doubly charged scalars in the type-II seesaw and its left-right extensions

Abstract

The type-II seesaw mechanism with an isospin-triplet scalar ΔL provides one of the most compelling explanations for the observed smallness of neutrino masses. The triplet contains a doubly-charged component HL±±, which dominantly decays to either same-sign dileptons or to a pair of W bosons, depending on the size of the triplet vacuum expectation value. However, there exists a range of Yukawa couplings fL of the triplet to the charged leptons, wherein a relatively light HL±± tends to be long-lived, giving rise to distinct displaced-vertex signatures at the high-energy colliders. We find that the displaced vertex signals from the leptonic decays HL±±→ℓα±ℓβ± could probe a broad parameter space with 10−10 ≲ |fL| ≲ 10−6 and 45.6GeV