Rare decay results from KTeV are reviewed, emphasizing modes that in principle provide information about the CKM matrix. Our recent results in lepton flavor violating modes are also presented.
The implications of the published KTeV $K^0_L to pi^0mu^+mu^-$ result for interpreting recent $Sigma^+ to pmu^+mu^-$ results are discussed. The status of the KTeV $Xi^0 to Sigma^+mu^- u$ analysis is given. The KTeV $|V_{us}|$ result is also given.
Recent results are presented for (1) the charge asymmetry in semielectronic kaon decay; (2) the charge radius of the neutral kaon; (3) the decay Klong -> pi0 pi0 e+e-; (4) constraints on rho(CKM) from kaon decays; (5) lepton flavor violation. A few w
ords about future kaon physics work at Fermilab are included.
We report on a new measurement of the branching ratio B(KL->pi0 gamma gamma)using the KTeV detector. We reconstruct 1982 events with an estimated background of 608, that results in B(KL -> pi0 gamma gamma) = (1.29 +/- 0.03(stat) +/- 0.05(syst)) x 10*
*-6. We also measure the parameter, aV, which characterizes the strength of vector meson exchange terms in this decay. We find aV = -0.31 +/- 0.05(stat) +/- 0.07(syst). These results utilize the full KTeV data set collected from 1997 to 2000 and supersede earlier KTeV measurements of the branching ratio and aV.
The KTeV collaboration at Fermi National Accelerator Laboratory has recently completed searches for and measurements of several decay modes of the neutral kaon and pion. These include new searches for lepton flavor violating decays (which have not be
en seen), and a new study of the parity properties of the decay pi^0 -> e^+e^-e^+e^-.
The problem of $rho$- and $omega$- mesons contributions to the background for $eta to pi^0 e^+e^-$ decay and to the asymmetries in the decays $eta to pi^+pi^-pi^0$ and $eta to pi^+pi^-gamma$ is considered.