A 125 GeV SM-like Higgs in the MSSM and the $γγ$ rate

TL;DR

The paper analyzes whether the MSSM can yield a SM-like Higgs around 125 GeV with a di-photon rate comparable to or above the SM prediction. It shows that achieving mh ≈ 125 GeV typically requires stops with substantial mixing (A_t) or a split stop spectrum, and discusses how Higgs mixing and loops from light charged states affect the γγ rate. While heavy stops generally keep the di-photon rate near or below the SM value, light staus with large mixing at high tanβ and μ can significantly enhance h→γγ without strongly altering gg→h. The findings highlight a viable MSSM path to the observed Higgs properties, with light staus as a particularly impactful possibility under certain parameter conditions.

Abstract

We consider the possibility of a Standard Model (SM)-like Higgs in the context of the Minimal Supersymmetric Standard Model (MSSM), with a mass of about 125 GeV and with a production times decay rate into two photons which is similar or somewhat larger than the SM one. The relatively large value of the SM-like Higgs mass demands stops in the several hundred GeV mass range with somewhat large mixing, or a large hierarchy between the two stop masses in the case that one of the two stops is light. We find that, in general, if the heaviest stop mass is smaller than a few TeV, the rate of gluon fusion production of Higgs bosons decaying into two photons tends to be somewhat suppressed with respect to the SM one in this region of parameters. However, we show that an enhancement of the photon decay rate may be obtained for light third generation sleptons with large mixing, which can be naturally obtained for large values of $\tanβ$ and sizable values of the Higgsino mass parameter.

Figures (4)

• Figure 1: Contour plots of the Higgs mass in the $m_{Q_3}$--$m_{u_3}$ plane, for different values of $A_t$ and $\tan\beta$. The stau soft masses have been fixed at $m_{L_3}^2 = m_{e_3}^2 = (350 \; {\rm GeV})^2$, while $\mu = 1030$ GeV and $A_\tau = 500$ GeV, leading to a lightest stau mass of about 135 GeV for $\tan\beta = 60$. The lightest stop masses are overlaid in dashed black lines.
• Figure 2: Contour plots of the Higgs mass in the plane of soft supersymmetry breaking parameters in the stop sector. In (a), we show the Higgs masses for $A_t=2.5$ TeV for three different values of $\tan\beta$, $\tan\beta = 5$ (dotted lines, green (grey) labels), $\tan\beta = 10$ (dashed lines, black labels) and $\tan\beta = 60$ (solid lines, green (grey) labels). The masses for $\tan\beta = 60$ shown are smaller than the ones for $\tan\beta = 10$ mostly due to the negative effects from the staus (see Eq. \ref{['eq:mhstau']}), and closer to the $\tan\beta = 5$ ones. In (b), the Higgs mass contours are shown for $m_{Q_3} = m_{u_3}$, varying the stop mixing parameter $A_t$. The stau supersymmetry breaking parameters have been kept at $m_{L_3}^2 = m_{e_3}^2 = (350 {\rm GeV})^2$ and $A_\tau = 500$ GeV, while $\mu = 1030$ GeV.
• Figure 3: Contour plots of the ratio of the $\sigma(gg \to h) \times$ BR($h \to \gamma \gamma$) to its SM value, in the $m_{Q_3}$--$m_{u_3}$ plane, for $\mu = 1030$ GeV.
• Figure 4: Contour plots of the ratio of the $\sigma(gg \to h) \times$ BR($h \to \gamma \gamma$) to its SM value, in the $m_{e_3}$--$m_{L_3}$ plane, for $\mu = 1030$ GeV, as well as in the $\mu$ --$m_{L_{3}}$ plane, for $m_{e_3} = m_{L_3}$, and $\tan\beta = 10$ (above) and $\tan\beta = 60$ (below). The red dashed lines are the contours at equal lightest stau masses. The yellow shaded area is the area satisfying the LEP bound on the lightest stau mass. Enhanced branching ratios are obtained for values of $\mu$ for which the stau mixing becomes relevant and the lightest stau mass is close to its experimental limit, of about 100 GeV.