Limitations and opportunities of off-shell coupling measurements

Abstract

Indirect constraints on the total Higgs width Γh from correlating Higgs signal strengths with cross-section measurements in the off-shell region for p(g)p(g)→4 production have received considerable attention recently, and the CMS Collaboration have published a first measurement. We revisit this analysis from a new physics and unitarity constraints perspective and conclude that limits on Γh obtained in this fashion are not reliable unless we make model-specific assumptions, which cannot be justified at the current stage of the LHC program. Relaxing the Γh interpretation, we discuss the merits of high invariant mass cross-section measurements in the context of Higgs CP analyses, higher-dimensional operator testing, and resolved new physics in the light of electroweak precision constraints beyond effective theory limitations. Furthermore, we show that a rather model-independent LHC constraint can be obtained from adapting the gg→4analysis to the weak boson fusion channels at lower statistical yield.