Doubly heavy baryons in sum rules of NRQCD

The masses of baryons containing two heavy quarks and their couplings to th e corresponding quark currents are evaluated in the framework of NRQCD sum rules. The Coulomb-like corrections in the system of doubly heavy diquark a re taken into account, and the contribution of nonperturbative terms coming from the quark, gluon and mixed condensates as well as the product of quar k and gluon condensates, is analyzed. The higher condensates destroy the fa ctorization of baryon and diquark correlators and provide the convergency o f sum rule method. As a result the accuracy of estimates is improved. (C) 2 000 Elsevier Science B.V. All rights reserved.