Implications of the LHC two-photon signal for two-Higgs-doublet models

Abstract

We study the implications for Two Higgs Doublet Models of the recent announcement at the LHC giving a tantalizing hint for a Higgs boson of mass 125 GeV decaying into two photons. We require that the experimental result be within a factor of two of the theoretical Standard Model prediction, and analyze the type I and type II models as well as the lepton-specific and flipped models, subject to this requirement. It is assumed that there is no new physics other than two Higgs doublets. In all of the models, we display the allowed region of parameter space taking the recent LHC announcement at face value, and we analyze the $W^+W^-$, $ZZ$, $\bar{b}b$ and $τ^+τ^-$ expectations in these allowed regions. Throughout the entire range of parameter space allowed by the $γγ$ constraint, the number of events for Higgs decays into $WW$, $ZZ$ and $b \bar b$ are not changed from the Standard Model by more than a factor of two. In contrast, in the Lepton Specific model, decays to $τ^+ τ^- $ are very sensitive across the entire $γγ$-allowed region.

Figures (4)

• Figure 1: For each of the four models discussed in the text, we plot the ratio $\frac{N_{2HDM}}{N_{SM}}$ in the ($\tan\beta,\sin\alpha$) plane for the $h\rightarrow\gamma\gamma$ signal. Along the red lines, the ratio is $1.0$, along the blue lines, it is $0.5$, and along the gold lines it is $2.0$. Requiring that the signal be between half and twice that of the SM restricts the parameter space to be between the gold and blue lines.
• Figure 2: For the type I and type II models discussed in the text, we plot the ratio $\frac{N_{2HDM}}{N_{SM}}$ in the ($\tan\beta,\sin\alpha$) plane for $h\rightarrow VV$, where $V=W,Z$. The result for the lepton-specific (flipped) models are very similar to those for type I (type II) models. Along the red lines, the ratio is $1.0$, along the blue lines, it is $0.5$, and along the gold lines it is $2.0$.
• Figure 3: For the type I and type II models discussed in the text, we plot the ratio $\frac{N_{2HDM}}{N_{SM}}$ in the ($\tan\beta,\sin\alpha$) plane for $h\rightarrow \bar{b}b$. The result for the lepton-specific (flipped) models are very similar to those for type I (type II) models. Along the red lines, the ratio is $1.0$, along the blue lines, it is $0.5$, and along the gold lines it is $2.0$. In the type I case, the ratio is less than $1.0$ for virtually all of the parameter space.
• Figure 4: For lepton-specific model, we plot the ratio $\frac{N_{2HDM}}{N_{SM}}$ in the ($\tan\beta,\sin\alpha$) plane for $h\rightarrow \tau^+ \tau^-$. Along the red lines, the ratio is $1.0$, along the blue lines, it is $0.5$, and along the gold lines it is $2.0$.