Lifetimes of doubly heavy baryons

We perform a detailed investigation of total lifetimes for the doubly heavy baryons ${\mathrm{\Xi }}_{Q{Q}^{\mathrm{\prime }}}$, ${\mathrm{\Omega }}_{Q{Q}^{\mathrm{\prime }}}$ in the framework of operator product expansion over the inverse heavy quark mass, whereas, to estimate matrix elements of operators obtained in OPE, approximations of nonrelativistic QCD are used.