How well do we need to measure Higgs boson couplings?

TL;DR

This paper explores the precision needed in measuring Higgs boson couplings to distinguish between the Standard Model and various new physics scenarios, providing target accuracy levels for future experiments.

Contribution

It defines what measurement precision is necessary for Higgs couplings to effectively test different beyond Standard Model theories.

Findings

Maximum allowed deviations depend on the new physics scenario.

Target measurement accuracies range from below 1% to 10% for vector bosons.

Fermion coupling deviations can be tens of percent.

Abstract

Most of the discussion regarding the Higgs boson couplings to Standard Model vector bosons and fermions is presented with respect to what present and future collider detectors will be able to measure. Here, we ask the more physics-based question of how well do we need to measure the Higgs boson couplings? We first present a reasonable definition of "need" and then investigate the answer in the context of various highly motivated new physics scenarios: supersymmetry, mixed-in hidden sector Higgs bosons, and a composite Higgs boson. We find the largest coupling deviations away from the SM Higgs couplings that are possible if no other state related to EWSB is directly accessible at the LHC. Depending on the physics scenario under consideration, we find targets that range from less than 1% to 10% for vector bosons, and from a few percent to tens of percent for couplings to fermions.