Off-shell effects in Higgs decays to heavy gauge bosons and signal-background interference in Higgs decays to photons at a linear collider

Abstract

We discuss off-shell contributions in Higgs decays to heavy gauge bosons $H\to V{V}^{(\ast )}$ with $V\in \{Z,W\}$ for a standard model (SM) Higgs boson for both dominant production processes $e^{+}{e}^{-}\to ZH\to ZV{V}^{(\ast )}$ and $e^{+}{e}^{-}\to \nu \bar{\nu }H\to \nu \bar{\nu }V{V}^{(\ast )}$ at a (linear) $e^{+}{e}^{-}$ collider. Dependent on the centre-of-mass energy off-shell effects are sizable and important for the understanding of the electroweak symmetry breaking mechanism. Moreover we shortly investigate the effects of the signal-background interference in $H\to \gamma \gamma$ decays for the Higgsstrahlung initiated process $e^{+}{e}^{-}\to Z\gamma \gamma$, where we report a similar shift in the invariant mass peak of the two photons as found for the LHC. For both effects we discuss the sensitivity to the total Higgs width.

Comments: 11 pages, 9 figures, talk presented at the International Workshop on Future Linear Colliders (LCWS14), Belgrade, Serbia, 6-10 October 2014