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The state χ c0 (3915) has recently been demoted by the Particle Data Group from its previous status as the conventional c¯ c 2 3 P0 state, largely due to the absence of expected D ¯ D decays. We propose that χ c0 (3915) is actually the lightest c¯ cs¯ s state, and calculate the spectrum of such states using the diquark model, identifying many of the… (More)

- Carl E. Carlson, Christopher D. Carone, Richard F. Lebed
- 2001

Jurčo, Möller, Schraml, Schupp, and Wess have shown how to construct noncommutative SU(N) gauge theories from a consistency relation. Within this framework, we present the Feynman rules for noncommutative QCD and compute explicitly the most dangerous Lorentz-violating operator generated through radiative corrections. We find that interesting effects appear… (More)

- Richard F. Lebed
- 1998

These lectures are designed to introduce the methods and results of large N c QCD in a presentation intended for nuclear and particle physicists alike. Beginning with definitions and motivations of the approach, we demonstrate that all quark and gluon Feynman diagrams are organized into classes based on powers of 1/N c. We then show that this result can be… (More)

We present precision corrections to dispersion relation bounds on form factors in bottom hadron semileptonic decays and analyze their effects on parameterizations derived from these bounds. We incorporate QCD two-loop and nonperturbative corrections to the two-point correlator, consider form factors whose contribution to decay rates is suppressed by lepton… (More)

- Richard F. Lebed
- 1997

We compute the nonleptonic weak decay width of a heavy-light meson in 1+1 spacetime dimensions with a large number of QCD colors (the 't Hooft model) as a function of the heavy quark mass. In this limit, QCD is exactly soluble, and decay modes are dominated by two-particle final states. We compare the results to the tree-level partonic decay width of the… (More)

We use rigorous QCD dispersion relations to derive model-independent bounds on the B → πlν, D → πlν and D → K lν form factors. These bounds are particularly restrictive when the value of the observable form factor at one or more kinematic points is assumed. With reasonable assumptions we find f B ≤ 195 MeV and that the shape of the form factor becomes… (More)

A new measurement of the Ξ 0 mass verifies the accuracy of the Coleman-Glashow relation at the level predicted by the 1/N c expansion. Values for other baryon isospin mass splittings are updated, and continue to agree with the 1/N c hierarchy.

- Richard F. Lebed
- 1996

We present the complete flavor SU(3) decomposition of decay amplitudes for decays of the triplet (B + u , B 0 d , B 0 s) of B mesons nonleptonically into two pseudoscalar mesons. This analysis holds for arbitrarily broken SU(3) and can be used to generate amplitude relations when physical arguments permit one to neglect or relate any of the reduced… (More)

- Carl E. Carlson, Christopher D. Carone, José L. Goity, Richard F. Lebed
- 1998

We consider in detail the mass operator analysis for the nonstrange ℓ = 1 excited baryons in large N c QCD. We present a straightforward procedure for constructing the large N c baryon wavefunctions, and provide complete analytic expressions for the matrix elements of all the independent isosin-glet mass operators. We discuss the relationship between the… (More)

We analyze the baryon mass differences up to second order in chiral perturbation theory, including the effects of decuplet intermediate states. We show that the Coleman–Glashow relation has computable corrections of order (m d − m u)m s. These corrections are numerically small, and in agreement with the data. We also show that corrections to the Σ… (More)