Correlation between the decays $h^0 \to \gamma \gamma/g g$ in the MSSM with quark flavour violation

Abstract

We study the loop-induced decays $h^0 \to \gamma \, \gamma$ and $h^0 \to g \, g$ in the Minimal Supersymmetric Standard Model (MSSM) with quark flavour violation (QFV), identifying $h^0$ with the Higgs boson with a mass of 125 GeV, where $\gamma$ and $g$ are photon and gluon, respectively. We perform a MSSM parameter scan and a detailed analysis around a fixed reference point respecting theoretical constraints from vacuum stability conditions and experimental constraints, such as those from B meson data and electroweak precision data, as well as recent limits on supersymmetric (SUSY) particle masses from LHC experiments. We find that (i) the relative deviation of the decay width $\Gamma(h^0 \to g \, g)$ from the Standard Model value, $DEV(g)$, can be large and negative, $\lesssim - 15\%$, (ii) the analogous deviation of $\Gamma(h^0 \to \gamma \, \gamma)$ is strongly correlated, $DEV(\gamma) \simeq -1/4\,DEV(g)$ for $DEV(g) \lesssim - 4\%$, (iii) the relative deviation of the width ratio $\Gamma(h^0 \to \gamma \, \gamma)/\Gamma(h^0 \to g \, g)$ from the SM value, $DEV(\gamma/g)$, can be large (up to $\sim$ 20\%), (iv) the deviations can be large due to the up-type squark loop contributions, (v) the SUSY QFV parameters can have a significant effect on these deviations. Such large deviations can be observed at a future $e^+e^-$ collider like ILC. Observation of the deviation patterns as shown in this study would favour the MSSM with flavour-violating squark mixings and encourage to perform further studies in this model.