The collider landscape: which collider for establishing the SM instability?

TL;DR

This paper discusses how future colliders could determine the Higgs potential's stability by precisely measuring the top quark mass and strong coupling, especially if no new physics is found.

Contribution

It proposes that low-energy colliders can accurately measure the top quark mass to assess the Standard Model's stability without assuming new physics.

Findings

Top quark mass can be measured precisely via $t ar t$ threshold scans.

Low-luminosity $e^+ e^-$ colliders can achieve necessary measurement accuracy.

Determining the Higgs potential instability scale is feasible with current collider technology.

Abstract

Capabilities of future colliders are usually discussed assuming specific hypothetical new physics. We consider the opposite possibility: that no new physics is accessible, and we want to learn if the unnatural Standard Model is part of a vast landscape. We argue that a main step in this direction would be establishing the possible instability scale of the Higgs potential. This primarily needs reducing the uncertainty on the strong coupling and on the top quark mass. We show that the top quark mass can be measured well enough via a $t \bar t$ threshold scan with low $10^{33}\,{\rm cm}^{-2}{\rm sec}^{-1}$ luminosity, that seems achievable at a `small' $e^+ e^-$ collider in the LEP tunnel, or at the first low-energy stage of a muon collider.