1 / 2 Enhancement and CP Violation for K → ππ , K → ππγ Weak Decays

Abstract Data indicate that ∆I=3/2 transitions account for 4.5–4.7% of both CP conserving and CP violating K→2π decays, as well as CP conserving radiative K→ππγ processes. Observed K → ππγ/ππ branching ratios are shown to scale near α/π or α/2π. The KL-KS mixing angle φ and the semileptonic weak-rate asymmetry δ are reviewed, and shown to be consistent with data. Also, K→ 2π ∆I =1/2 dominance is studied in the context of the chiral constituent quark model, displaying again excellent agreement with data. Finally, indirect and direct kaon CP violation are successfully described in the framework of photon-mediated loop graphs.