9 research outputs found
Measurement of K^+ \to \pi^0 \mu^+ \nu \gamma decay using stopped kaons
The K^+ \to \pi^0 \mu^+ \nu \gamma () decay has been
measured with stopped positive kaons at the KEK 12 GeV proton synchrotron. A
sample containing 125 events was obtained. The partial
branching ratio was found to be , which is in good agreement with theoretical predictions.Comment: 12 pages, 3 figures, to be published in Physics Letters
Measurement of direct photon emission in decay using stopped positive kaons
The radiative decay () has
been measured with stopped positive kaons. A sample
containing 4k events was analyzed, and the branching ratio
of the direct photon emission process was determined to be . No interference pattern with internal
bremsstrahlung was observed.Comment: 12 pages, 6 figures, 2 tables, to be published in Phys. Lett.
Apparatus for a Search for T-violating Muon Polarization in Stopped-Kaon Decays
The detector built at KEK to search for T-violating transverse muon
polarization in K+ --> pi0 mu+ nu (Kmu3) decay of stopped kaons is described.
Sensitivity to the transverse polarization component is obtained from
reconstruction of the decay plane by tracking the mu+ through a toroidal
spectrometer and detecting the pi0 in a segmented CsI(Tl) photon calorimeter.
The muon polarization was obtained from the decay positron asymmetry of muons
stopped in a polarimeter. The detector included features which minimized
systematic errors while maintaining high acceptance.Comment: 56 pages, 30 figures, submitted to NI
Search for the decay K+ to pi+ gamma gamma in the pi+ momentum region P>213 MeV/c
We have searched for the K+ to pi+ gamma gamma decay in the kinematic region
with pi+ momentum close to the end point. No events were observed, and the 90%
confidence-level upper limit on the partial branching ratio was obtained, B(K+
to pi+ gamma gamma, P>213 MeV/c) < 8.3 x 10-9 under the assumption of chiral
perturbation theory including next-to-leading order ``unitarity'' corrections.
The same data were used to determine an upper limit on the K+ to pi+ gamma
branching ratio of 2.3 x 10-9 at the 90% confidence level.Comment: 15 pages, 3 figures; no change in the results, accepted for
publication in Physics Letters
Measurement of ratio using stopped positive kaons
The ratio of the () and () decay widths, , has been measured with stopped positive kaons.
and samples containing 2.4 and 4.0 events, respectively, were analyzed. The
ratio was obtained to be
0.6710.007(stat.)0.008(syst.) calculating the detector acceptance by
a Monte Carlo simulation with the assumption of - universality in
decay. The coefficient of the dependent term of the form
factor was also determined to be
=0.0220.005(stat.)0.004(syst.).Comment: 12 pages, 6 figure
Development of electronics and data acquisition system for the J-PARC T59 (WAGASCI) experiment
International audienceWAGASCI is a new experiment at J-PARC neutrino beamline, to measure the cross section ratio of charged current neutrino interaction on nucleus between water target and plastic target with the accuracy of a few percent. The detector adopts three-dimensional grid structure of 3-mm- thick scintillator bars around water and plastic targets, to obtain large angular acceptance. As a photodetector a 32-channel arrayed MPPC has been developed for the WAGASCI detector. The WAGASCI detector has 1280 MPPC channels in total. Our front-end electronics is SPIROC2D, which is an auto-triggered, bi-gain, 36-channel ASIC, allowing to measure the charge from one to 2000 photoelectron and the time with 100ps step. It contains a 16-deep analog memory array, which allows to store 16 hits in an acquisition gate. The back-end boards control the data output from the front-end ASIC and reception of trigger signals for neutrino beam. The module con- struction has been completed and the data acquisition system has almost been completed, to be ready for the neutrino beam measurement from October 2017