Reconstructing Higgs boson properties from the LHC and Tevatron data

TL;DR

The paper performs a global phenomenological fit to Higgs boson data from ATLAS, CMS, CDF, and D0 after Moriond 2012, allowing all Higgs branching fractions, couplings, and an invisible width to vary. It finds that while the SM with a 125 GeV Higgs provides an acceptable fit, the data are better described by scenarios with suppressed loop-induced gg rates and enhanced gamma gamma rates, and with an upper bound on invisible decays around BR(inv) < 0.4. The analysis also explores fermiophobic and dysfermiophilic possibilities, supersymmetric implications, dark matter portal models, and a radion interpretation, showing that several beyond-SM scenarios can accommodate the observed pattern, though with varying degree of statistical preference. The results emphasize that more data are needed to confirm whether the observed anomalies are statistical fluctuations or genuine signs of new physics in the Higgs sector, and to distinguish between a Higgs-like boson and a radion.

Abstract

We perform a phenomenological fit to all ATLAS, CMS, CDF and D0 Higgs boson data available after Moriond 2012. We allow all Higgs boson branching fractions, its couplings to standard model particles, as well as to an hypothetical invisible sector to vary freely, and determine their current favourite values. The standard model Higgs boson with a mass 125 GeV correctly predicts the average observed rate and provides an acceptable global fit to data. However, better fits are obtained by non-standard scenarios that reproduce anomalies in the present data (more γγ and less WW signals than expected), such as modified rates of loop processes or partial fermiophobia. We find that present data disfavours Higgs boson invisible decays. We consider implications for the standard model, for supersymmetric and fermiophobic Higgs bosons, for dark matter models, for warped extra-dimensions.

Figures (5)

• Figure 1: Left: The Higgs boson rate favoured at $1\sigma$ (dark blue) and $2\sigma$ (light blue) in a global SM fit as function of the Higgs boson mass. Right: assuming $m_h=125\,{\rm GeV},$ we show the measured Higgs boson rates at ATLAS, CMS, CDF, D0 and their average (horizontal gray band at $\pm1\sigma$). Here 0 (red line) corresponds to no Higgs boson, 1 (green line) to the SM Higgs boson.
• Figure 2: Predictions for the Higgs boson rates in different scenarios: SM, free branching ratios of loop processes, free couplings, radion, top-phobic and fermiophobic, defined via eqs. (\ref{['allrates']},\ref{['simplerates']},\ref{['radionrate']}).
• Figure 3: Left: fit for the Higgs boson branching fraction to photons and gluons. In yellow with continuous contour-lines: global fit. In gray with dotted contour-lines: the fermiophobic Higgs boson searches are excluded from the data-set. Red dashed curve: the possible effect of extra top partners, such as the stops. Right: fits for the invisible Higgs boson branching fraction, under different model assumptions, as explained in section \ref{['inv']}.
• Figure 4: Left: fit of the Higgs boson couplings assuming common rescaling factors $a$ and $c$ with respect to the SM prediction for vector bosons and fermions, respectively. Right: fit to the $t$-quark and to $b$-quark and $\tau$-lepton Yukawa couplings assuming the SM couplings to gauge bosons. The best fit presently lies somehow away from the SM prediction, indicated in the figures as 'SM'. The point marked as 'FP' is the fermiophobic case, and '0t' denotes the top-phobic case. Negative values of the top Yukawa coupling are preferred because lead of an enhancement of $h\to \gamma\gamma$.
• Figure 5: Global fit for the Higgs boson couplings to vectors, to the $t$-quark, to the $b$-quark, to the $\tau$ lepton. All these couplings are freely varied and in each panel we show the $\chi^2$ as function of the parameters indicated on the axes, marginalised with respect to all other parameters. We again assume $m_h=125\,{\rm GeV}$ and find that the best fit presently lies somehow away from the SM prediction, indicated in the figures as 'SM'.