Higgs Decay Branching Ratios

The total decay rate of the Higgs boson is given by the sum of the partial decay rates (into various final states), ${\Gamma }_h={\sum }_f\Gamma (h\to f)$. But this assumption holds only approximately since, e.g., the states $b\bar{b}$ and $c\bar{c}$ are both characterised by total angular momentum $J=0$, vanishing beauty and charm $B=0=C$, and vanishing baryon number. The amplitudes for the mixing $b\bar{b}\to c\bar{c}$ are QCD-induced and therefore very small at high scales such as $M_h$.

The branching ratio of the Higgs boson is defined as $\mathcal{B}(h\to f)=\frac{\Gamma (h\to f)}{{\Gamma }_h}$.