A search for inclusive muon-neutrino (v^) oscillations has been performed in the Fermilab narrow-band neutrino beam using two detectors running simultaneously at two distances from the neutrino source. The data show no evidence for a distance dependence of the neutrino flux and rule out oscillations of v^ into any other single type of neutrino for 30 < Am 2 < 1000 eV 2 /c 4 and sin 2 (20) > 0.02-0.20.

We report on a new measurement of the branching ratio B(KL → π 0 γγ) using the KTeV detector. We reconstruct 1982 events with an estimated background of 608, that results in B(KL → π 0 γγ) = (1.29 ± 0.03stat ± 0.05syst) × 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 ± 0.05stat ± 0.07syst. 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 recent discovery of a large CP violating asymmetry in KL-->pi+pi-e+e- mode has prompted us to seach for the associated KL-->pi 0 pi 0 e+e- decay mode in the KTeV-E799 experiment at Fermilab. In 2.7 x 10(11) K(L) decays, one candidate event has been observed with an expected background of 0.3 event, resulting in an upper limit for the KL-->pi 0 pi 0 e+e- branching ratio of 6.6 x 10(-9) at the 90% C.L.

The branching ratio of the rare decay 0 ! e e ÿ has been measured precisely, using the complete data set from the KTeV E799-II experiment at Fermilab. We observe 794 candidate 0 ! e e ÿ events using K L ! 3 0 as a source of tagged 0 s. The expected background is 52:7 11:2 events, predominantly from high e e ÿ mass 0 ! e e ÿ decays. We have measured B 0 ! e e ÿ ; m e e ÿ =m 0 2 > 0:95 6:44 0:25 stat 0:22 syst 10 ÿ8 , which is above the unitary bound from 0 ! and within the range of theoretical expectations from the standard model.

Fermilab experiment E773 has measured the phases 4+ = 43. 53'~0 . 97' and 400 -4+