No abstract

In contrast to the nonleptonic decays of charmed baryons B, -B( i ' + P (0-), where the decay amplitude receives contributions both from the s-channel and u-channel .IP= f' poles and from the factorization term, the Cabibbo-favored decays B, -B( ++, decuplet)+P(O-) or V( 1 -) are much simpler to describe. In general, one finds that either the pole term (we confine ourselves to i ' poles only) or the factorization term contributes, but not both. In this paper we have considered the Cabibbo-favored decays of A:,S:A,STA, and 0:. In the model where only i ' poles are kept, we find that A: and E:A decays receive contributions from s-channel poles only and that 0: decays into B( t+, decuplet)+ P ( 0 -) or V( 1-) through the factorization process only. S: A decays are forbidden. We make numerical estimates of decay rates and the asymmetry parameters. We emphasize that the decays B,-B(++, decuplet) + P(O-) or V ( 1 -) are theoretically "clean" and simple to describe and that data in these decay modes will be very desirable.PACS number(s): 13.30.Eg, 14.20.K~

We study the form factors of heavy-to-heavy and heavy-to-light weak decays using the light-front relativistic quark model. For the heavy-to-heavy B~D ' semileptonic decays we calculate the corresponding Isgur-Wise function for the whole kinematic region. For the heavy-to-light B -+ P and B~V semileptonic decays we calculate the form factors at q = 0; in particular, we have derived the dependence of the form factors on the 6-quark mass in the m&~oo limit. This dependence cannot be produced by extrapolating the scaling behavior of the form factors at q "using the single-pole assumption. This shows that the q dependence of the form factors in regions far away from the zero recoil could be much more complicated than that predicted by the single-pole assumption.

We use the relativistic light-front quark model to show that both strong and radiative D * decays are in good agreement with the 1992 CLEO II results. In particular the coupling for D * → Dπ is consistent with the experimental upper limit. The key point is the relativistic treatment of the quark spin.

The exclusive rare decay B → K * γ takes place in a region of maximum recoil, q 2 = 0, posing a problem for nonrelativistic quark models which are usually thought to be most reliable at zero recoil. The Bauer-Stech-Wirbel (BSW) model, formulated in the infinite-momentum-frame (IMF) formalism, is designed to work at q 2 = 0. We show in this model that the ratio relating the decay B → K * γ and the q 2 -spectrum of the semileptonic decay B → ρeν, becomes independent of the wave function in the SU(3) flavor symmetry limit. We show that this feature is also true in relativistic quark models formulated in the IMF or light-cone formalism, if the b quark is infinitely heavy. In fact, these relativistic models, which have a different spin structure from the BSW case, reduce to the BSW model in the heavy b-quark limit. A direct measurement of the q 2 -spectrum of the semileptonic decay can therefore provide accurate information for the exclusive rare decay.