Preasymptotic effects in beauty decays

Large preasymptotic effects in beauty decays have been found using heavy-quark and SU(3) symmetry, as well as experimental data on charmed hyperons. Contrary to rather uniform beauty-meson lifetimes, a much larger spread of beauty-baryon lifetimes is predicted. However, it is highly unlikely that, theoretically, the $\tau ({\mathrm{\Lambda }}_b)\mathrm{/}\tau (B_d^0)$ ratio, which at present deviates more than $1\sigma$ from the experimental result, can be lowered below 0.9.