A sensitivity target for an impactful Higgs boson self coupling measurement

Abstract: We argue that a measurement of the Higgs boson self-coupling becomes particularly meaningful in a large and important class of theories when its sensitivity is within 40\% of its Standard Model value. This constitutes a target for a future impactful experimental achievement. It is derived from recently obtained results of how extreme the differences can be between effective field theory operator coefficients when their origins are from reasonable custodial-violating theories beyond the Standard Model.