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abstract: 'We perform a detailed investigation of total lifetimes for the doubly heavy baryons $\Xi_{QQ''}$, $\Omega_{QQ''}$ 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.'
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[**Lifetimes of doubly heavy baryons**]{}\
A.K. Likhoded$^{a)}$, A.I. Onishchenko$^{b)}$\
\
[*Protvino, Moscow region, 142284 Russia*]{}\
[b) Institute for Theoretical and Experimental Physics]{}\
[*Moscow, B. Cheremushkinskaja, 25, 117259 Russia\
Fax: 7 (095) 123-65-84*]{}

Introduction
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At present a number of powerful techniques based on Operator Product Expansion (OPE) and effective field theories have been developed. These tools allow one consistently to include into consideration various nonperturbative contributions, written in terms of a few number of universal quantities. The coefficients (Wilson coefficients) in front of these operators are generally expanded in series over the QCD coupling constant, inverse heavy quark mass and/or relative velocity of heavy quarks inside the hadron. The accuracy, obtained in such calculations, can be systematically improved, and it is limited only by the convergence properties of the mentioned series. The described approach have been already widely used for making the precise 