A NOVEL APPROACH TO ABS. (DELTA I) = 1/2 RULE AND DELTA(V) = 0 RULE (SELECTION, CURRENT ALGEBRA)

摘要

Current algebra and low energy theorems (PCAC and soft-meson extrapolation) have formed part of a well-established theory of weak interactions since the early 1960's. It is to be fully shown in this dissertation that a more fruitful, theoretical framework emerges when one dynamical ansatz supplements the previous theory; the ansatz is called level realization.;With the aid of asymptotic SU(,f)(N) symmetry, various selection rules are obtained on the same footing, along with other important physical quantities (such as the value of g(,A)(0), and the smallness of iso-scalar nucleon magnetic moments, etc.), through the procedure of level realization of chiral SU(,f)(N)(,L)(CRTIMES)SU(,f)(N)(,R) algebras. The level realization ansatz should be compared with a saturation assumption; the former contains the latter as a special case. It is shown that both the (VBAR)(DELTA)I(VBAR) = 1/2 rule for the asymptotic two-particle weak vertices and the OZI rule must simultaneously be satisfied in the case of helicity (lamda) = 1. We then find that the realization pattern should be universal in order to sustain the asymptotic (VBAR)(DELTA)I(VBAR) = 1/2 rule for the helicity (lamda) = 0 case. On the same ground, the charm counterpart of the asymptotic (VBAR)(DELTA)I(VBAR) = 1/2 rule proves to be the asymptotic (DELTA)V = 0 rule (conservation of the V-spin and V(,3)). The observed approximate (VBAR)(DELTA)I(VBAR) = 1/2 rule in the kaon decays is derived from the asymptotic (VBAR)(DELTA)I(VBAR) = 1/2 rule by using a new soft-pion extrapolation. The asymptotic (DELTA)V = 0 rule also leads to the approximate (DELTA)V = 0 rule in the charm-meson decays. The violations of the two rules result from the so-called surface term in the new soft-meson approximation. This point is discussed qualitatively.