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The state χc0(3915) has recently been demoted by the Particle Data Group from its previous status as the conventional cc̄ 2P0 state, largely due to the absence of expected DD̄ decays. We propose that χc0(3915) is actually the lightest cc̄ss̄ state, and calculate the spectrum of such states using the diquark model, identifying many of the observed… (More)

A new measurement of the Ξ mass verifies the accuracy of the ColemanGlashow relation at the level predicted by the 1/Nc expansion. Values for other baryon isospin mass splittings are updated, and continue to agree with the 1/Nc hierarchy. 11.15.Pg, 14.20.-c,13.40.Dk Typeset using REVTEX ejenkins@ucsd.edu lebed@jlab.org The recent measurement of the Ξ mass… (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)

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
- 1998

These lectures are designed to introduce the methods and results of large Nc 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/Nc. We then show that this result can be… (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 (md − mu)ms. These corrections are numerically small, and in agreement with the data. We also show that corrections to the Σ… (More)

- Stanley J Brodsky, Richard F Lebed
- Physical review letters
- 2009

The "true microonium" (micro+micro-) and "true tauonium" (tau+tau-) bound states are not only the heaviest, but also the most compact pure QED systems. The rapid weak decay of the tau makes the observation of true tauonium difficult. However, as we show, the production and study of true microonium is possible at modern electron-positron colliders.

We use both old and new theoretical developments in QCD dispersion relation constraints on the scalar form factor in the decay K → πlνl to obtain constraints on the strange quark mass. The perturbative QCD side of the calculation incorporates up to four-loop corrections, while the hadronic side uses a recently developed parameterization constructed… (More)

- Alfredo Aranda, Christopher D. Carone, Richard F. Lebed
- 1999

We present a model of fermion masses based on a minimal, non-Abelian discrete symmetry that reproduces the Yukawa matrices usually associated with U(2) theories of flavor. Mass and mixing angle relations that follow from the simple form of the quark and charged lepton Yukawa textures are therefore common to both theories. We show that the differing… (More)

- Richard F. Lebed
- 1994

We compute and tabulate the Clesbsch–Gordan coefficients of the SU(6) ⊃ SU(3) × SU(2) product 56 ⊗ 56, which are relevant to the nonrelativistic spin-flavor symmetry of the lightest baryons. Under the assumption that the largest representation in this product, the 2695, gives rise to operators in a chiral expansion that produce numerically small effects, we… (More)