| Summary: | 博士 === 國立清華大學 === 物理學系 === 87 === We calculate the long distance contribution to K+→π+νν￣ and KL→π0νν￣ within the framework of chiral perturbation theory (CHPT) up to O(p4). The result comes from the weak lagrangian of O(p4) which we derived from the factorization model, and the one-loop diagrams from O(p2) actions. We estimate the branching ratios and give a comparison to the results from the short distance contribution. We find that B(K+→π+νν￣) from long distance contribution is about 4-5 order smaller than that of the short distence effect, while the decay of KL→π0νν￣ receives no contribution from long distance effect. For the decay KL→π+π-νν￣, we study both CP-conserving and -violating contributions. We find that the decay branching ratio is dominated by the CP-conserving part. In the standard CKM model, we estimate that for mt~174 GeV, the branching ratio due to the CP-conserving (-violating) contributions can be as large as 4.4 ×10-13(1.0×10-14). We also calculate the long distance contributions in K→ππνν￣ andπππνν￣ modes within the framework of chiral perturbation theory. We find that these contributions to decay rates of K→ππνν￣ in the chiral logarithmic approximation are at least seven orders of magnitude suppressed relative to those from the short distance parts. The long distance effects in this class of decays are, therefore, negligible.
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