The flavor and spin symmetry of the heavy quarks and the spontaneously broken approximate SU(3), X SU(3), chiral symmetry of the light quarks are exploited to formulate a theory describing the low-energy interactions of the heavy mesons (Qg bound states) and heavy baryons (Qq,qz bound states) with the Goldstone bosons a, K, and 7. The theory contains only three parameters independent of the number of heavy-quark species involved. They can be determined by the decays D*+D +a, Zc+Ac +a, and Z:+ZC +n-. Theoretically, these coupling constants are related, through partial conservation of axial-vector current, to the axial charges of the heavy mesons and the heavy baryons. They are all calculable in the nonrelativistic quark model by using the spin wave functions of these particles alone. The theory is applied to strong decays and semileptonic weak decays of the heavy mesons and baryons. The implications are also discussed.
Within the light-front framework, form factors for P→ P and P→V transitions ͑P denotes a pseudoscalar meson, V a vector meson͒ 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→V transition. Some of the P→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. ͓S0556-2821͑97͒06503-X͔
The radiative decays of heavy mesons and heavy baryons are studied in a formalism which incorporates both the heavy quark symmetry and the chiral symmetry. The chiral Lagrangians for the electromagnetic interactions of heavy hadrons consist of two pieces: one from gauging electromagnetically the strong-interaction chiral Lagrangian, and the other from the anomalous magnetic moment interactions of the heavy baryons and mesons. Due to the heavy quark spin symmetry, the latter contains only one independent coupling constant in the meson sector and two in the baryon sector. These coupling constants only depend on the light quarks and can be calculated in the nonrelativistic quark model. However, the charm quark is not heavy enough and the contribution from its magnetic moment must be included. Applications to the radiative decays D * → Dγ , B * → Bγ , Ξ ′ c → Ξ c γ , Σ c → Λ c γ and Σ c → Λ c πγ are given. Together with our previous results on the strong decay rates of D * → Dπ and Σ c → Λ c π, predictions are obtained for the total widths and branching ratios of D * and Σ c . The decays Σ + c → Λ + c π 0 γ and Σ 0 c → Λ + c π − γ are discussed to illustrate the important roles played by both the heavy quark symmetry and the chiral symmetry.
Motivated by the observation of the decayB →K * γ by CLEO, we have systematically analyzed the two-body weak radiative decays of bottom and charmed hadrons. There exist two types of weak radiative decays: One proceeds through the short-distance b → sγ transition and the other occurs through W -exchange accompanied by a photon emission. Effective Lagrangians are derived for the W -exchange bremsstrahlung processes at the quark level and then applied to various weak electromagnetic decays of heavy hadrons. Predictions for the branching ratios ofB presented. Within this approach, the decay asymmetry for antitriplet to antitriplet heavy baryon weak radiative transitions is uniquely predicted by heavy quark symmetry. The electromagnetic penguin contribution to Λ 0 b → Λγ is estimated by two different methods and its branching ratio is found to be of order 1 × 10 −5 . We conclude that weak radiative decays of bottom hadrons are dominated by the short-distance b → sγ mechanism.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.