of order of $45\%$ in the case of doubly charmed baryons and less then $5\%$ in the case of $(bbq)$ - baryons.

to 1.5cm to 17.5cm

to 1.5cm to 17.5cm

to 1.5cm to 17.5cm

to 1.5cm to 17.5cm

to 1.5cm to 17.5cm

to 1.5cm to 17.5cm

to 1.5cm to 17.5cm

to 1.5cm to 17.5cm

to 1.5cm to 17.5cm

Conclusion
==========

In the present paper we have performed a detail investigation and numerical estimates for the lifetimes of doubly heavy baryons. The used approach is based on OPE expansion of total widths for the corresponding hadrons, and it is combined with the formalism of effective fields theories developed previously. In this way, we have accounted for the both perturbative QCD and mass corrections to the Wilson coefficients of operators. The nonspectator effects, presented by Pauli interference and weak scattering, and their influence on the total lifetimes are considered. The obtained results show the significant role played by them in the description of lifetimes of doubly heavy baryons.

The authors thank V.V.Kiselev for fruitful discussions and remarks concerning the presentation of results.

This work is in part supported by the Russian Foundation for Basic Research, grants 96-02-18216 and 96-15-96575. The work of 