A Minimal Flavor Violating 2HDM at the LHC

TL;DR

The paper analyzes a minimal flavor-violating two-Higgs-doublet model (MFV-2HDM) in which both Higgs doublets couple to up-type and down-type fermions with MFV-aligned Yukawas, allowing independent control of hbȳb and hττ while keeping gauge- and top-couplings close to the SM. It demonstrates that MFV-2HDM can accommodate the observed h→γγ enhancements via reduced total width or charged-Higgs-loop effects, while predicting correlated changes in h→bb and h→WW/ZZ rates; it also explores scenarios with one or two light Higgs bosons and analyzes heavy-Higgs phenomenology, including quasi-decoupling and potential discovery prospects up to M_H ≲ 350 GeV. The charged-Higgs sector in MFV is shown to be less constrained than in Type II, permitting sizable loop-induced h→γγ effects and a broader viable parameter space. Overall, MFV provides a flexible framework that fits current Higgs data and yields testable predictions for heavy Higgs searches and charged-Higgs contributions.

Abstract

We explore the phenomenology of a two Higgs doublet model where both Higgs doublets couple to up-type and down-type fermions with couplings determined by the minimal flavor violation ansatz. This 2HDM "Type MFV" generalizes 2HDM Types I-IV, where the decay rates of h --> bb and h --> tau+tau- are governed by MFV couplings independent of the Higgs couplings to gauge bosons or the top quark. To determine the implications of the present Higgs data on the model, we have performed global fits to all relevant data. Several surprisingly large effects on the light Higgs phenomenology can arise: (1) The modified couplings of the Higgs to fermions can enhance the h --> gamma gamma rate significantly in both VBF production (up to a factor of 3 or more) and the inclusive rate (up to a factor of 1.5 or more). (2) In the 2HDM Type MFV, the constraints on a light charged Higgs are milder than in 2HDM Types I-IV. Thus, there can be substantial charged Higgs loop contribution to the di-photon rate, allowing further enhancements of the di-photon rates. (3) The h --> tau+tau- rate can be (highly) suppressed, independently of the other decay channels. Furthermore, we studied the correlation between the light Higgs and the heavy Higgs phenomenology. We showed that even small deviations from the decoupling limit would imply good prospects for the detection of the heavy Higgs boson. In some regions of parameter space, a substantial range of M_H is already either ruled out or on the edge of detection. Finally we investigated the possibility that the heavy Higgs is close in mass to the light Higgs, providing additional h/H --> bb rate, as well as confounding the extraction of properties of the Higgs bosons.

Figures (7)

• Figure 1: Best fit regions in the $\xi_V^h$ -- $\xi_t^h$ (left), $\xi_b^h$ -- $\xi_t^h$ (middle), and $\xi_b^h$ -- $\xi_\tau^h$ (right) planes in a $\chi^2$ fit of the data to one Higgs boson at 125 GeV. The light green, green and dark green regions correspond to the $\Delta \chi^2 =$1, 4, and 9 regions. The red labeled contours in the left plot show constant values of $\tan\beta$. In the middle plot the region shaded in orange shows the parameter space that is accessible in a 2HDM Type II by varying $\xi_V^h$ within its $1\sigma$ range. The blue solid curves in the middle and right plot exemplarily show regions of parameter space that can be reached in the MFV 2HDM by varying $\xi_V^h$ within the $1\sigma$ range, while keeping the other parameters fixed to the indicated values (dotted lines correspond to $\xi_V^h$ outside the $1\sigma$ range). For the blue curves in the right plot we fix $\tan\beta = 0.78$ and $\epsilon_b = -1.52$ to the best fit values. The gray region in the left plot with $\xi_t^h < 0$ corresponds to a second minimum in the $\chi^2$, that is however excluded by searches for the heavy scalar $H$ (see text).
• Figure 2: Results for various Higgs rates normalized to the SM rates from a fit of the data to the 2HDM Type MFV with one light scalar boson at 125 GeV. For comparison results from an analogous fit in the 2HDM Type II and the experimental $1\sigma$ ranges are also shown. The black stars correspond to the best fit values. The circles indicate an example scenario with strongly enhanced VBF $h \to \gamma \gamma$ signal.
• Figure 3: Current 95% C.L. exclusion bounds normalized to the predicted cross sections for the heavy Higgs as function of the heavy Higgs mass $M_H$. Shown are $H \to ZZ \to 4\ell$ (light blue), $H \to ZZ \to \ell \ell \nu\nu$ (dark blue), $H \to WW \to \ell\nu \ell\nu$ (green), $H \to \tau^+\tau^-$ (dark red), and $H \to b\bar{b}$ (orange). The top (center) plot corresponds to the best fit values of the light Higgs couplings with $\xi_b^h >0$ ($\xi_b^h < 0$). In the bottom plot we allow for a larger $\xi_\tau^h$ coupling such that the inclusive $h\to\tau^+\tau^-$ rate is 50% of the corresponding SM rate.
• Figure 4: Best fit regions in the $\xi_V^h$ -- $\xi_t^h$ (left), $\xi_b^h$ -- $\xi_t^h$ (middle), and $\xi_b^h$ -- $\xi_\tau^h$ (right) planes in a $\chi^2$ fit of the data to two Higgs bosons at 125 GeV and 135 GeV, respectively. The dark green, green and light green regions correspond to the $\Delta \chi^2 =$1, 4, and 9 regions. The red labeled contours in the left plot show constant values of $\tan\beta$. In the middle plot the region shaded in orange shows the parameter space that is accessible in a 2HDM Type II by varying $\xi_V^h$ within its $1\sigma$ range. The blue solid curves in the middle and right plot exemplarily show regions of parameter space that can be reached in the MFV 2HDM by varying $\xi_V^h$ within the $1\sigma$ range, while keeping the other parameters fixed to the indicated values. For the blue curves in the right plot we fix $\tan\beta = 6.7$ and $\epsilon_b = -0.57$ to the best fit values.
• Figure 5: Results for various Higgs rates normalized to the SM rates from a fit of the data to the 2HDM Type MFV with two light scalar bosons at 125 GeV and 135 GeV. For comparison, results from an analogous fit in the 2HDM Type II and the experimental 1$\sigma$ ranges are also shown. The black stars correspond to the best fit values.