Flavoured searches for type-III seesaw at the LHC

TL;DR

This paper reinterprets CMS LHC searches for type-III seesaw lepton triplets, revealing significant sensitivity to tau couplings and providing a flexible way to present limits for various masses and flavor mixings.

Contribution

It demonstrates that existing searches are effective for triplets with tau couplings and introduces a method to present limits without simplifying flavor assumptions.

Findings

Good sensitivity to tau-dominated triplets in trilepton final states

Limits can be generalized for arbitrary masses and flavor mixings

Common assumptions about flavor couplings are unnecessary and should be reconsidered.

Abstract

We present a reinterpretation of CMS searches for type-III seesaw lepton triplets at the LHC, both for the normal and the inverse seesaw. We find that, in contrast with previous expectations, these searches in the trilepton final state have a good sensitivity to triplets with predominant coupling to the tau lepton. We also show that the limits resulting from direct searches can be neatly presented for arbitrary masses and general flavour mixings. Thus, it turns out that the common (and often unrealistic) simplifying assumptions about the flavour couplings of the triplets used by experimental collaborations to present their results are unnecessary and should be dropped.