Baryons with two heavy quarks

Basic physical characteristics of doubly heavy baryons are examined, including spectroscopy (which is treated in the potential approach and within the QCD sum rules framework), production mechanisms for various interactions (the fragmentation model with preasymptotic twist corrections of higher order in the baryon transverse momentum), inclusive decays and lifetimes (operator expansion in the inverse powers of the heavy quark masses), and exclusive decays (in the QCD sum rules framework). The effective theory of heavy quarks is extended to systems with two heavy quarks and one light quark. The masses, decay widths and yields of doubly heavy baryons are calculated for the experimental facilities now being operated or planned. Prospects for the detection and observation of such baryons are discussed. The most interesting physical effects involving hadrons are analyzed and their impact on the theory of heavy quark dynamics is considered.