Singlet model interference effects with high scale UV physics

One of the simplest extensions of the Standard Model (SM) is the addition of a scalar gauge singlet, $S$. If $S$ is not forbidden by a symmetry from mixing with the Standard Model Higgs boson, the mixing will generate non-SM rates for Higgs production and decays. In general, there could also be unknown high energy physics that generates additional effective low energy interactions. We show that interference effects between the scalar resonance of the singlet model and the effective field theory (EFT) operators can have significant effects in the Higgs sector. We examine a non-$Z_2$ symmetric scalar singlet model and demonstrate that a fit to the 125 GeV Higgs boson couplings and to limits on high mass resonances, $S$, exhibit an interesting structure and possible large cancellations of effects between the resonance contribution and the new EFT interactions, that invalidate conclusions based on the renormalizable singlet model alone.

Figure 1

Regions allowed by the requirement that the electroweak minimum be a global minimum for $\cos \theta =0.94$, $b_4=1$ and $m_2=400$, 600, and 750 GeV [9].

Figure 2

Allowed decay widths for $h_2\to h_1{h}_1$ assuming the parameters correspond to a global minimum of the potential for $b_4=1$, $\cos \theta =0.94$, and $m_2=400$, 600 and 750 GeV.

Figure 3

Branching ratio for (left-hand side) $h_1\to WW$, and (right-hand side) $h_1\to ZZ$ for representative values of the parameters.

Figure 4

Branching ratios for (left-hand side) $h_1\to \gamma \gamma$, and (right-hand side) $h_1\to Z\gamma$ for representative values of the parameters.

Figure 5

95% confidence level allowed regions using the gluon fusion signal strength for $h_1$ production (red) and allowed regions derived from fits to the signal strengths given in Eq. (21) (black) [15] with $\mathrm{\Lambda }=2\mathrm{TeV}$. Only the linear terms in the EFT expansion are included.

Figure 6

95% confidence level allowed regions obtained by varying $c_{gg}$, $c_{WW}$, $c_{BB}$, $\cos \theta$, along with $b_1$, $b_3$ and $a_2$, allowed by the 8 TeV and 13 TeV resonance searches of Tables 1 and 2.

Figure 7

Allowed regions combining $h_1$ and $h_2$ data and a narrow width $\mathrm{\Gamma }(h_2)/m_2<0.05$ restriction. The new physics scale is set $\mathrm{\Lambda }=2\mathrm{TeV}$, and $c_{WW}$, $c_{BB}$ are scanned over.