P. Debu

Simultaneous measurement of KS and KL decays into π+π-γ

With the E731 apparatus at Fermilab, we have simultaneously collected 6859 [ital K][sub [ital L]] and [ital K][sub [ital S]] decays into [pi][sup +][pi][sup [minus]][gamma]. Using our sample of over 370 000 [pi][sup +][pi][sup [minus]] decays for normalization we have determined that the ratio [Gamma]([ital K][sup 0][r arrow][pi][sup +][pi][sup [minus]][gamma])/[Gamma]([ital K][sup 0][r arrow][pi][sup +][pi][sup [minus]]) is (23.0[plus minus]0.7)[times]10[sup [minus]3] for [ital K][sub [ital L]] and (7.10[plus minus]0.22)[times]10[sup [minus]3] for [ital K][sub [ital S]], for photon energies greater than 20 MeV in the kaon center of mass. After removing the inner-bremsstrahlung contribution, we find that the photon energy spectrum of the direct emission decay of the [ital K][sub [ital L]] is consistent with the presence of a vector meson propagator in the form factor.

New limits on KL,S--> pi 0e+e-

Data taken in a Fermilab experiment designed to measure to CP-violation parameter epsilon/epsilonfrom a study of K..-->..2..pi.. decays were used to look for the as yet unseen decay modes K/sub L//sub ,//sub S/..--> pi../sup 0/e/sup +/e/sup -/. The detector was optimized for the detection of kaon decays with four electromagnetic showers in the final state. The results (90% confidence) are branching ratios pi../sup 0/e/sup +/e/sup -/ and K/sub S/..--> pi../sup 0/e/sup +/e/sup -/, respectively.

Simultaneous measurement of KS and KL decays into pi + pi - gamma.

With the E731 apparatus at Fermilab, we have simultaneously collected 6859 [ital K][sub [ital L]] and [ital K][sub [ital S]] decays into [pi][sup +][pi][sup [minus]][gamma]. Using our sample of over 370 000 [pi][sup +][pi][sup [minus]] decays for normalization we have determined that the ratio [Gamma]([ital K][sup 0][r arrow][pi][sup +][pi][sup [minus]][gamma])/[Gamma]([ital K][sup 0][r arrow][pi][sup +][pi][sup [minus]]) is (23.0[plus minus]0.7)[times]10[sup [minus]3] for [ital K][sub [ital L]] and (7.10[plus minus]0.22)[times]10[sup [minus]3] for [ital K][sub [ital S]], for photon energies greater than 20 MeV in the kaon center of mass. After removing the inner-bremsstrahlung contribution, we find that the photon energy spectrum of the direct emission decay of the [ital K][sub [ital L]] is consistent with the presence of a vector meson propagator in the form factor.

Simultaneous measurement of [ital K][sub [ital S]] and [ital K][sub [ital L]] decays into [pi][sup +][pi][sup [minus]][gamma]

With the E731 apparatus at Fermilab, we have simultaneously collected 6859 [ital K][sub [ital L]] and [ital K][sub [ital S]] decays into [pi][sup +][pi][sup [minus]][gamma]. Using our sample of over 370 000 [pi][sup +][pi][sup [minus]] decays for normalization we have determined that the ratio [Gamma]([ital K][sup 0][r arrow][pi][sup +][pi][sup [minus]][gamma])/[Gamma]([ital K][sup 0][r arrow][pi][sup +][pi][sup [minus]]) is (23.0[plus minus]0.7)[times]10[sup [minus]3] for [ital K][sub [ital L]] and (7.10[plus minus]0.22)[times]10[sup [minus]3] for [ital K][sub [ital S]], for photon energies greater than 20 MeV in the kaon center of mass. After removing the inner-bremsstrahlung contribution, we find that the photon energy spectrum of the direct emission decay of the [ital K][sub [ital L]] is consistent with the presence of a vector meson propagator in the form factor.

Simultaneous measurement ofKSandKLdecays intoπ+π−γ

With the E731 apparatus at Fermilab, we have simultaneously collected 6859 [ital K][sub [ital L]] and [ital K][sub [ital S]] decays into [pi][sup +][pi][sup [minus]][gamma]. Using our sample of over 370 000 [pi][sup +][pi][sup [minus]] decays for normalization we have determined that the ratio [Gamma]([ital K][sup 0][r arrow][pi][sup +][pi][sup [minus]][gamma])/[Gamma]([ital K][sup 0][r arrow][pi][sup +][pi][sup [minus]]) is (23.0[plus minus]0.7)[times]10[sup [minus]3] for [ital K][sub [ital L]] and (7.10[plus minus]0.22)[times]10[sup [minus]3] for [ital K][sub [ital S]], for photon energies greater than 20 MeV in the kaon center of mass. After removing the inner-bremsstrahlung contribution, we find that the photon energy spectrum of the direct emission decay of the [ital K][sub [ital L]] is consistent with the presence of a vector meson propagator in the form factor.

Measurement of the [ital CP]-violation parameter [eta][sub +[minus][gamma]] in neutral kaon decays

Interference between [ital K][sub [ital S]] and [ital K][sub [ital L]] decays into the final state [pi][sup +][pi][sup [minus]][gamma] has been observed in experiment 731 at Fermilab. By fitting the distribution of decays downstream of a regenerator, a new CP-violation parameter [eta][sub +[minus][gamma]], analogous to [eta][sub +[minus]], has been measured, with its magnitude equal to (2.15[plus minus]0.26[plus minus]0.20)[times]10[sup [minus]3], and [phi][sub +[minus][gamma]], the associated phase angle, equal to (72[plus minus]23[plus minus]17)[degree]. Assuming that any difference between this fit value for [eta][sub +[minus][gamma]] and the previously measured value for [eta][sub +[minus]] can be attributed to direct CP violation in this decay, a limit of [vert bar][ital e][sub +[minus][gamma]][sup [prime]][vert bar]/[epsilon][lt]0.3 at the 90% confidence level has been made.

Measurement of the CP-violation parameter η+-γ in neutral kaon decays

Interference between [ital K][sub [ital S]] and [ital K][sub [ital L]] decays into the final state [pi][sup +][pi][sup [minus]][gamma] has been observed in experiment 731 at Fermilab. By fitting the distribution of decays downstream of a regenerator, a new CP-violation parameter [eta][sub +[minus][gamma]], analogous to [eta][sub +[minus]], has been measured, with its magnitude equal to (2.15[plus minus]0.26[plus minus]0.20)[times]10[sup [minus]3], and [phi][sub +[minus][gamma]], the associated phase angle, equal to (72[plus minus]23[plus minus]17)[degree]. Assuming that any difference between this fit value for [eta][sub +[minus][gamma]] and the previously measured value for [eta][sub +[minus]] can be attributed to direct CP violation in this decay, a limit of [vert bar][ital e][sub +[minus][gamma]][sup [prime]][vert bar]/[epsilon][lt]0.3 at the 90% confidence level has been made.

Measurement of the CP-Violation Parameterη+−γin Neutral Kaon Decays

Interference between [ital K][sub [ital S]] and [ital K][sub [ital L]] decays into the final state [pi][sup +][pi][sup [minus]][gamma] has been observed in experiment 731 at Fermilab. By fitting the distribution of decays downstream of a regenerator, a new CP-violation parameter [eta][sub +[minus][gamma]], analogous to [eta][sub +[minus]], has been measured, with its magnitude equal to (2.15[plus minus]0.26[plus minus]0.20)[times]10[sup [minus]3], and [phi][sub +[minus][gamma]], the associated phase angle, equal to (72[plus minus]23[plus minus]17)[degree]. Assuming that any difference between this fit value for [eta][sub +[minus][gamma]] and the previously measured value for [eta][sub +[minus]] can be attributed to direct CP violation in this decay, a limit of [vert bar][ital e][sub +[minus][gamma]][sup [prime]][vert bar]/[epsilon][lt]0.3 at the 90% confidence level has been made.

Search for KL--> pi 0 gamma gamma.

A search for the rare decay mode /ital K//sub /ital L///r arrow//pi//sup 0//gamma//gamma/ was performed using a data set from Fermilab experiment E-731. The decay is of interest in the context of chiral perturbation theory and for its contribution to the decay /ital K//sub /ital L///r arrow//pi//sup 0/e/sup +/e/sup /minus//. The result is /ital B/(/ital K//sub /ital L///r arrow//pi//sup 0//gamma//gamma/)/lt/2.7 /times/10/sup /minus/6/ (90% confidence level) which is nearly a two-order-of magnitude improvement over the previous best limit.

Search for KL0

A search for the rare decay mode /ital K//sub /ital L///r arrow//pi//sup 0//gamma//gamma/ was performed using a data set from Fermilab experiment E-731. The decay is of interest in the context of chiral perturbation theory and for its contribution to the decay /ital K//sub /ital L///r arrow//pi//sup 0/e/sup +/e/sup /minus//. The result is /ital B/(/ital K//sub /ital L///r arrow//pi//sup 0//gamma//gamma/)/lt/2.7 /times/10/sup /minus/6/ (90% confidence level) which is nearly a two-order-of magnitude improvement over the previous best limit.