Is the resonance at 125 GeV the Higgs boson?

TL;DR

The paper tests whether the 125 GeV resonance is the Standard Model Higgs by performing model‑independent fits to collider data, allowing deviations in tree‑level Higgs couplings, loop‑level processes, and an invisible width. Using a global rate‑based framework with m_h fixed to the best‑fit value, the authors find that W/Z couplings are broadly SM‑like while the γγ channel shows a persistent excess that can be accommodated by modified Yukawa couplings or new loop contributions. They explore scenarios including dilaton/radion mixing and a Type II two‑Higgs‑doublet model, showing current data already place meaningful constraints on these possibilities. The study demonstrates how rate fits across channels constrain Higgs properties and guide future measurements to identify potential new physics in the Higgs sector.

Abstract

The recently discovered resonance at 125 GeV has properties remarkably close to those of the Standard Model Higgs boson. We perform model-independent fits of all presently available data. The non- standard best-fits found in our previous analyses remain favored with respect to the SM fit, mainly but not only because the γγ rate remains above the SM prediction.

Figures (7)

• Figure 1: Left: assuming $m_h=125.5\,{\rm GeV},$ 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. Right: The Higgs boson rate favored at $1\sigma$ (dark blue) and $2\sigma$ (light blue) in a global SM fit as function of the Higgs boson mass.
• Figure 2: Left: determination of SM Higgs boson production cross-sections compared with SM theoretical uncertainties (smaller gray ellipses). Right: fit as function of the Higgs/dilaton mixing (0 corresponds to pure Higgs boson, and 1 to pure dilaton).
• Figure 3: Predictions for the Higgs boson rates in different scenarios: SM, free branching ratios of loop processes, free couplings, dilaton.
• Figure 4: Left: fit for the Higgs boson branching fraction to photons and gluons. The red dashed curve shows the possible effect of extra top partners, such as the stops. Right: fits for the invisible Higgs boson branching fraction (see section \ref{['inv']} for the model assumptions).
• Figure 5: Left: fit of the Higgs boson couplings assuming common rescaling factors $a$ and $c$ with respect to the SM prediction for couplings to 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 point marked as 'SM' is the Standard Model; the point marked as 'FP' is the fermiophobic case, and '0t' denotes the top-phobic case.