We review the experimental and theoretical status of baryons containing one heavy quark. The charm and bottom baryon states are classified and their mass spectra are listed. The appropriate theoretical framework for the description of heavy baryons is the Heavy Quark Effective Theory, whose general ideas and methods are introduced and illustrated in specific examples. We present simple covariant expressions for the spin wave functions of heavy baryons including p--wave baryons. The covariant spin wave functions are used to determine the Heavy Quark Symmetry structure of flavour--changing current--induced transitions between heavy baryons as well as one--pion and one--photon transitions between heavy baryons of the same flavour. We discuss $1/m_Q$ corrections to the current--induced transitions as well as the structure of heavy to light baryon transitions. Whenever possible we attempt to present numbers to compare with experiment by making use of further model--dependent assumptions as e.g. the constituent picture for light quarks. We highlight recent advances in the theoretical understanding of the inclusive decays of hadrons containing one heavy quark including polarization. For exclusive semileptonic decays we discuss rates, angular decay distributions and polarization effects. We provide an update of the experimental and theoretical status of lifetimes of heavy baryons and of exclusive nonleptonic two body decays of charm baryons.Comment: 93 pages, 18 figures not included, latex, DESY 94-095, MZ-THEP-94-0

Namely, the qualitative features of the multipole structure of each resonance are governed by one coupling ratio each. The results of recent multipole analyses indicate that these coupling ratios are approximately the same 1n all three cases. Our analysis supports the contention made by some authors that the N -6 form factor falls with one power faster asymptotically than that corresponding to canonical dipole behaviour.

We derive QCD sum rules for heavy baryons at leading order in 1/m Q and at next-to-leading order in α S . The calculation involves the evaluation of four different perturbative three-loop diagrams which determine the α S -corrections to the Wilson coefficients of the leading term in the Operator Product Expansion (OPE). From the sum rules we obtain estimates for the masses and the residues of the heavy baryons Λ Q and Σ Q . The perturbative O(α S ) corrections to the leading order spectral function amount to about 100%, and they shift the calculated values for the baryon masses slightly upward. The residues are shifted upward by about 20 − 50%. For the bound state energyΛ given by the difference of the heavy baryon mass and the pole mass of the heavy quark m Q we obtain m Λ Q − m Q ∼ = 780 MeV and m Σ Q − m Q ∼ = 950 MeV . For the residues we find |F Λ | ∼ = 0.028 GeV 3 and |F Σ | ∼ = 0.039 GeV

We calculate the transition form factors that occur in heavy ⌳-type baryon semileptonic decays such as, e.g., in ⌳ b →⌳ c ϩ ϩl Ϫ ϩ l . We use Bauer-Stech-Wirbel-type infinite momentum frame wave functions for the heavy ⌳-type baryons which we assume to consist of a heavy quark and a light spin-isospin zero diquark system. The form factors at q 2 ϭ0 are calculated from the overlap integrals of the initial and final ⌳-type baryon states. To leading order in the heavy mass scale the structure of the form factors agrees with the HQET predictions including the normalization at zero recoil. The leading order dependence of the form factors is extracted by scaling arguments. By comparing the model form factors with the HQET predictions at O(1/m Q ) we obtain a consistent set of model form factors up to O(1/m Q ). With our preferred choice of parameter values we find that the contribution of the nonleading form factor is practically negligible. We use our form factor predictions to compute rates, spectra, and various asymmetry parameters for the semileptonic decay ⌳ b →⌳ c ϩ ϩl Ϫ ϩ l .

We analyze τ lepton decay observables, namely moments of the hadronic spectral density in the finite energy interval (0, M τ ), within finite order perturbation theory including α 4 s corrections. The start of the asymptotic growth of the perturbation theory series is found at this order in a scheme invariant manner. We establish the ultimate accuracy of finite order perturbation theory predictions and discuss the construction of optimal observables.