T. K. Komatsubara

Further evidence for the decay K+ ---> pi+ neutrino anti-neutrino

Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211<P<229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 pm 0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.

Further Evidence for the DecayK+→π+νν¯

Additional evidence for the rare kaon decay K+ to pi+ neutrino-antineutrino has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211<P<229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 pm 0.05 events. The branching ratio is B=1.57^{+1.75}_{-0.82} 10^{-10}.

Further search for the decay K+-->pi(+)nunu;

A search for additional evidence for the rare kaon decay K^+ -->pi^+ nu nubar has been made with a new data set comparable in sensitivity to the previous exposure that produced a single event.A search for additional evidence for the rare kaon decay K{sup +}{yields}{pi}{sup +}{nu}{nu} (bar sign) has been made with a new data set comparable in sensitivity to the previous exposure that produced a single event. No new events were found in the pion momentum region examined, 211<P<229 MeV/c . Including a reanalysis of the original data set, the backgrounds were estimated to contribute 0.08{+-}0.02 events. Based on one observed event, the new branching ratio is B(K{sup +}{yields}{pi}{sup +}{nu} {nu}(bar sign))=1.5{sup +3.4}{sub -1.2}x10{sup -10} . (c) 2000 The American Physical Society.

Measurement of structure-dependent K+ --> m(+)nu(m)gamma decay

We report the first measurement of a structure dependent component in the decay K^+ ->mu^+ nu gamma. Using the kinematic region where the muon kinetic energy is greater than 137 MeV and the photon energy is greater than 90 MeV, we find that the absolute value of the sum of the vector and axial-vector form factors is |F_V+F_A| =0.165 pm 0.007 pm 0.011. This corresponds to a branching ratio of BR(SD^+) = (1.33 pm 0.12 pm 0.18) times 10^{-5}. We also set the limit -0.04

Development of a Neutral Beam Profile Monitor

We developed a novel beam profile monitor for measuring the shape of an intense neutral beam for particle physics. This monitor is based on a detector technology of scintillating fibers, photomultiplier tubes, and sampling ADCs. It has an advantage for its simplicity, reliability, flexibility, and versatility. This monitor was installed in the small-diameter neutral beam for the KL0 →π0 νν experiment at J-PARC. We report in this article the development and performance of this monitor.

Long-lived neutral-kaon flux measurement for the KOTO experiment

The KOTO (

Photon-veto counters at the outer edge of the endcap calorimeter for the KOTO experiment

K^0

Kaons - Recent Results and Future Plans

at Tokai) experiment aims to observe the CP-violating rare decay

Measurement of Structure-Dependent K+→μ+νμγ Decay

K_L rightarrow pi^0 nu bar{nu}

Search for the Decay K+ -> pi+ pi0 nu nubar

by using a long-lived neutral-kaon beam produced by the 30 GeV proton beam at the Japan Proton Accelerator Research Complex. The