Off-shell Higgs coupling measurements in BSM scenarios

Abstract

Proposals of measuring the off-shell Higgs contributions and first measurements at the LHC have electrified the Higgs phenomenology community for two reasons: firstly, probing interactions at high invariant masses and momentum transfers is intrinsically sensitive to new physics beyond the Standard Model, irrespective of a resonant or non-resonant character of a particular BSM scenario. Secondly, under specific assumptions a class of models exists for which the off-shell coupling measurement together with a measurement of the on-shell signal strength can be re-interpreted in terms of a bound on the total Higgs boson width. In this paper, we provide a first step towards a classification of the models for which a total width measurement is viable and we discuss examples of BSM models for which the off-shell coupling measurement can be important in either constraining or even discovering new physics in the upcoming LHC runs. Specifically, we discuss the quantitative impact of the presence of dimension six operators on the (de)correlation of Higgs on-and off-shell regions keeping track of all interference effects. We furthermore investigate off-shell measurements in a wider context of new (non-)resonant physics in Higgs portal scenarios and the MSSM.

The Higgs legacy of the LHC Run I

“…Finally, we include off-shell measurements of Higgs production [31][32][33] in the SFitter analysis and estimate their current impact. While it has been established that off-shell measurements will not serve as model-independent measurements of the Higgs width [34][35][36][37][38], we can establish their role in hypothesis-based Higgs studies.…”

“…Note that ∆ g in this representation shows a non-trivial momentum dependence, limiting the model-independent features of the width measurement [34][35][36][37][38]. If the Higgs propagator in the interference is probed far above the mass shell, it behaves like 1/s.…”

Probing the top-quark width through ratios of resonance contributions of e + e − → W + W − b b ¯ $$ {\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mathrm{W}}^{+}{\mathrm{W}}^{-}\mathrm{b}\overline{\mathrm{b}} $$

“…1 The latter relation can be severely affected by Beyond-the-Standard Model (BSM) physics as discussed in refs. [41][42][43][44] for the LHC and in ref. [36] for a linear collider.…”

Interference effects in heavy Higgs production via gluon fusion in the singlet extension of the Standard Model

“…This phenomenon has already been noticed in ref. [27] where however it was dismissed as numerically irrelevant.…”