Probing the nature of the Higgs-like Boson via h -> VF decays

TL;DR

Addresses how to determine the nature of the Higgs-like scalar by examining off-shell vector boson decays to general final states. Introduces a general amplitude decomposition into Lorentz structures and an EFT parameterization to connect observables to Wilson coefficients. Demonstrates that differential spectra, especially in h to V F leptonic channels and rare h to VP decays, offer complementary information beyond global signal-strength fits and can reveal CP properties and custodial-symmetry patterns. The framework provides a pathway to constrain independent EFT operators and to illuminate the Higgs sector and vacuum structure.

Abstract

We give a general decomposition of the h -> VF amplitude where V={W,Z} and F is a generic leptonic or hadronic final state, in the standard model (SM), and in the context of a general effective field theory. The differential distributions for F=l^+l^-, l nu (l =e, mu) are reported, and we show how such distributions can be used to determine modified Higgs couplings that cannot be directly extracted from a global fit to Higgs signal strengths. We also demonstrate how rare h -> VP decays, where P is a single hadron, with SM rates in the 10^{-5} range, can be used to provide complementary information on the couplings of the newly discovered Higgs-like scalar and are an interesting probe of the vacuum structure of the theory.

Figures (1)

• Figure 1: ${\rm d} \Gamma/{\rm d} {q}^2$ and ${\rm d}\Gamma/{\rm d} y_1$ spectra (arbitrary units) for different values of EFT parameters chosen to leave the total rate unchanged. The plots are for $V=Z$, and in both plots the black (full) curve corresponds to the SM, $c_i=(1,0,0)$, the red (dotted) curve is for $c_i=(0.82,-0.8,0.8)$, the green (dashed) curve for $c_i=(1.18,0.5,-0.6)$, and the blue (dash-dotted) curve for $c_i=( 1.30, 1.5, -1.5)$. The curves in the upper plot accidentally pass through a common point, for our choice of parameters. The values of $c_i$ have been chosen for illustrative purposes, and are a bit larger than expected from EFT power counting. NDA Manohar:1983md indicates that $c_{2,3} \sim \mathcal{O}(v^2/\Lambda^2)$ and $c_1 - 1 \sim \mathcal{O}(v^2/\Lambda^2)$. The left plots are for $m_V=m_Z$, and the right plots are convoluted with a Breit-Wigner distribution of width $\Gamma_Z$ over the mass range $m_Z \pm 10$ GeV.