Vectorlike leptons are an intriguing possibility for physics beyond the Standard Model. We study the reach for discovering (at $5\sigma$ significance) or excluding (at 95% confidence) models of charged vectorlike leptons that mix predominantly with the tau, using multilepton signatures at various future proton-proton collider options: a high-luminosity LHC with $\sqrt{s}=14\mathrm{TeV}$, a high-energy LHC with $\sqrt{s}=27\mathrm{TeV}$, and possible new longer-tunnel colliders with $\sqrt{s}=70$ or 100 TeV. For weak-isodoublet vectorlike leptons, we estimate that a 27 TeV high-energy LHC with $15{\mathrm{ab}}^{-1}$ could exclude masses up to about 2300 GeV, or discover them if the mass is less than about 1700 GeV, while a 100 TeV collider with $30{\mathrm{ab}}^{-1}$ could exclude masses up to about 5750 GeV or make a discovery if the mass is less than about 4000 GeV. However, we find that weak-isosinglet vectorlike leptons present a much more difficult challenge, with some reach for exclusion, but not for discovery at any of the collider options considered.

• Received 8 May 2019

DOI:https://doi.org/10.1103/PhysRevD.100.015033

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society