New Higgs interactions and recent data from the LHC and the Tevatron

TL;DR

This work performs a broad, model-independent global fit to Higgs data from ATLAS, CMS, and the Tevatron to quantify how much the observed scalar can deviate from SM expectations. By allowing independent up-type and down-type fermion couplings, separate $HWW$ and $HZZ$ couplings, and loop-induced modifications via $x_g$ and $x_\gamma$, plus a phase in the top sector and an invisible width, the authors map the viable parameter space using a seven-parameter $\\chi^2$ analysis. The results show that 95% CL departures from the SM are still compatible, with notable implications when a nonzero top-quark phase is included and when custodial symmetry is relaxed, including a potentially sizeable invisible width. The study provides a framework for interpreting Higgs data that remains applicable as more data accumulate, highlighting regions where new physics could lurk in Higgs couplings and loop processes.

Abstract

We perform a multi-parameter global analysis of all data available till date from the ATLAS, CMS and Tevatron experiments, on the signals of a Higgs boson, to investigate how much scope exists for departure from the standard model prediction. We adopt a very general and model-independent scenario, where separate deviations from standard model values are possible for couplings of the observed scalar with up-and down-type fermions, W-and Z-boson pairs, as well as gluon and photon pair effective interactions. An arbitrary phase in the coupling with the top-pair, and the provision for an invisible decay width for the scalar are also introduced. After performing a global fit with seven parameters, we find that their values at 95% confidence level can be considerably different from standard model expectations. Moreover, rather striking implications of the phase in top-quark coupling are noticed. We also note that the invisible branching ratio can be sizeable, especially when the couplings of the Higgs to W-and Z-pairs are allowed to be different.

Figures (4)

• Figure 1: Two-dimensional contour plots for $68\%$ and $95\%$ confidence intervals, for case A, with rest of the parameters fixed at their best-fit values. The best-fit point is also marked separately by a '$*$'. In this case $\delta$ has been fixed at $0$, whereas $0\leq \beta_W,\beta_Z\leq2.0$, and $\beta_W \neq \beta_Z$.
• Figure 2: Two-dimensional contour plots for $68\%$ and $95\%$ confidence intervals, for case B, with rest of the parameters fixed at their best-fit values. The best-fit point is also marked separately by a '$*$'. In this case $\delta$ has been varied in the range $\{0,\pi\}$, whereas $0.92\leq \beta\leq 1.18$, with $\beta \equiv \beta_W =\beta_Z$.
• Figure 3: Variation of the $\chi^2$ function with the invisible branching fraction of $H$ ($\epsilon$) in cases A (left panel) and B (right panel). In case A, $\delta=0$ and $\beta_W \ne \beta_Z$, whereas in case B, $\delta$ has been varied in the range $\{0,\pi\}$ and $0.92\leq \beta\leq 1.18$, with $\beta \equiv \beta_W =\beta_Z$.
• Figure 4: Variation of the $\chi^2$ function with the phase in the up-type quark Yukawa coupling, $\delta$, in case B. In this case $\delta$ has been varied in the range $\{0,\pi\}$, whereas $0.92\leq \beta\leq 1.18$, with $\beta \equiv \beta_W =\beta_Z$.