Chi-Yee Cheung

Mesonic form factors and the Isgur-Wise function on the light front

Within the light-front framework, form factors for P{r_arrow}P and P{r_arrow}V transitions (P denotes a pseudoscalar meson, V a vector meson) due to the valence-quark configuration are calculated directly in the entire physical range of momentum transfer. The behavior of the form factors in the infinite quark mass limit are examined to see if the requirements of heavy-quark symmetry are satisfied. We find that the Bauer-Stech-Wirbel-type light-front wave function fails to give a correct normalization for the Isgur-Wise function at zero recoil in P{r_arrow}V transition. Some of the P{r_arrow}V form factors are found to depend on the recoiling direction of the daughter mesons relative to their parents. Thus the inclusion of the nonvalence contribution arising from quark-pair creation is mandatory in order to ensure that the physical form factors are independent of the recoiling direction. The main feature of the nonvalence contribution is discussed. {copyright} {ital 1997} {ital The American Physical Society}

Corrections to chiral dynamics of heavy hadrons: 1/M correction.

In earlier publications we have analyzed the strong and radiative decays of heavy hadrons in a formalism which incorporates both heavy-quark and chiral symmetries. In particular, we have derived a heavy-hadron chiral Lagrangian whose coupling constants are related by the heavy-quark flavor-spin symmetry arising from the QCD Lagrangian with infinitely massive quarks. In this paper, we reexamine the structure of the above chiral Lagrangian by including the effects of 1/{ital m}{sub {ital Q}} corrections in the heavy-quark effective theory. The relations among the coupling constants, originally derived in the heavy-quark limit, are modified by heavy-quark symmetry-breaking interactions in QCD. Some of the implications are discussed.

Light-Front Heavy Quark Effective Theory and Heavy Meson Bound States

The heavy-quark effective theory is developed on the light front. Based on this effective theory, a light-front heavy-meson bound state with definite spin and parity is constructed. Within the effective theory, the Isgur-Wise function is derived in terms of the asymptotic light-front bound state amplitudes in the limit {ital m}{sub {ital Q}}{r_arrow}{infinity}; the result is a general expression for arbitrary recoil velocities. With the asymptotic form of the BSW amplitudes, the Isgur-Wise function is given by {xi}({ital v}{center_dot}{ital v}{prime})=1/{ital v}{center_dot}{ital v}{prime}. The slope at the zero-recoil point is {rho}{sup 2}={minus}{xi}{prime}(1)=1, in excellent agreement with the recent CLEO result of {rho}{sup 2}=1.01{plus_minus}0.15{plus_minus}0.09.

Heavy-Flavor-Conserving Hadronic Weak Decays of Heavy Baryons

A bstractMore than two decades ago, we studied heavy-flavor-conserving weak decays of heavy baryons within the framework that incorporates both heavy-quark and chiral symmetries. In view of the first observation of Ξb− → Λb0π− by LHCb recently, we have reexamined these decays and presented updated predictions. The predicted rates for Ξb− → Λb0π− in the MIT bag and diquark models are consistent with experiment. The major theoretical uncertainty stems from the evaluation of baryon matrix elements. The branching fraction of Ξc → Λcπ is predicted to be of order 10−4. It is suppressed relative to ℬΞb→Λbπ

TOWARD THE UNDERSTANDING OF K→3π DECAYS IN CHIRAL PERTURBATION THEORY

\mathrm{\mathcal{B}}\left({\Xi}_b\to {\Lambda}_b\pi \right)

Heavy quark and chiral symmetry predictions for semileptonic decays B-bar-->D(D*) pi l nu -bar.

owing to the shorter lifetime of Ξc relative to Ξb and the destructive nonspectator W-exchange contribution. The kinematically accessible weak decays of the sextet heavy baryon ΩQ are ΩQ → ΞQπ. Due to the absence of the ℬ6−ℬ3−

B → πlΝ form factors calculated on the light-front

{\mathrm{\mathcal{B}}}_6-{\mathrm{\mathcal{B}}}_{{}_3^{-}}