We make comments on baryon semileptonic decays motivated by recent work on quark models. We find the decay rate of A,-*AFv to be reduced by a factor of 2 from its naive value due to wave-function distortion and form-factor effects. Configuration mixing implies the value of +0.04 for the vector-to-axial-vector ratio in 1 *-+,AP decay.Small changes in SU, predictions due to configuration mixing are also discussed. The Appendix describes a very simple method of evaluation of the axial-vector-to-vector ratio in the symmetric quark model with static quarks.A small but positive p r o g r e s s h a s occurred in our understanding of the spectrum and strong decays of baryons following ideas conjectured from quantum c h r o m~d y n a m i c s .~ Two ideas received special emphasis: (a) the effects of different quark m a s s e s in a universal, flavor-independent, confining potential; and (b) the effects of configuration mixing induced by quark hyperfine interactions? The purpose of this paper is to discuss some simple consequences of these ideas on baryon semileptonic decays. Thus, we discuss corrections to Cabibbo theo~-y.4 Since Cabibbo theory is known t o work well, many of the corrections we discuss a r e small and will require very accurate measurements f o r their confirmation. We emphasize that this paper does not give a complete description of any of the topics it deals with, but only comments on the few features suggested by the quark-model work alluded to above.We s t a r t by discussing a m a s s effect. Several authors2 have noted that the assumption of flavorindependent confining forces leads t o a distortion of the orbital wave function of a hadron containing a heavy quark Q relative t o the orbital wave function of a hadron composed of light quarks only. This can change, for example, the expectation value of the hyperfine interaction in one hadron t o a different value in the other one. In the present context, we recall that the transition amplitude for the semileptonic decay of a heavy baryon into a light baryon contains, a t low momentum transfer, the overlap integral of the orbital wave functions of the two hadrons:(1) and this overlap will be smaller than unity if the two wave functions a r e not i d e n t i~a l .~ The overlap integral can be estimated in a harmonic-oscillator model where it is Here a, and a2 a r e p a r a m e t e r s describing the relevant oscillators in the initial and final states:The quantity I 2 is one of the f a c t o r s in the decay r a t e of the initial hadron into the final hadron.The p a r a m e t e r s a, and a , depend on the quark m a s s e s and the only case in which I differs perceptibly from unity is that of a baryon containing a charmed o r a heavier quark ( b , t ) . In the approximation of neglecting the light-quark m a s s relative to the heavy-quark m a s s we find and therefore a diminution of the semileptonic decay r a t e of a charmed baryon by about 10% from i t s value predicted on the assumption of undistorted wave functions.It should be remembered that the...
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