The branching ratio of the structure dependent (SD) radiative K+→e+νeγ decay relative to that of the K+→e+νe(γ) decay including the internal bremsstrahlung (IB) process (Ke2(γ)) has been measured in ...the J-PARC E36 experiment using plastic scintillator/lead sandwich detectors, in contrast to the previous E36 measurement, which used a CsI(Tl) calorimeter. In the analysis, the effect of IB was also taken into account in the SD radiative decay as Ke2γ(γ)SD. By combining the new data with the previous E36 result after revision for the IB correction for Ke2γ(γ)SD, a new value Br(Ke2γ(γ)SD)/Br(Ke2(γ))=1.20±0.07 has been determined. This is consistent with a recent lattice QCD calculation, but larger than the expectation of Chiral Perturbation Theory (ChPT) at order O(p4) and the previous KLOE value. Using the method to relate form factor and branching ratio described in the KLOE paper, the present result is also consistent with the form factor prediction based on a gauged nonlocal chiral quark model, but larger than that from ChPT at order O(p6).
The structure dependent radiative K+→e+νγ (Ke2γSD+) decay was investigated with stopped positive kaons. The e+ momentum spectra containing 574±30Ke2γSD+ events with a K+→μ+ν (Kμ2) background of 28±19 ...events were measured with and without a photon in coincidence and analyzed with Monte Carlo simulations for acceptance and detector response to extract the ratio of the branching ratio of the Ke2γSD+ decay and the K+→e+ν decay including the internal bremsstrahlung process (Ke2(γ)). A value of Br(Ke2γSD+)/Br(Ke2(γ))=1.12±0.07stat±0.04syst was obtained. This indicates a partial branching ratio, Br(Ke2γSD+,pe>200MeV/c,Eγ>10MeV)/Br(Kμ2)=(1.85±0.11stat±0.07syst)×10−5, which is 25% (∼2.5σ) higher than the previous experimental result.
A new type of a trigger-scintillation counter array designed for the MTV experiment at TRIUMF-ISAC has been developed, which uses aluminum-metallized film tape for wrapping to achieve the required ...assembling precision of ±0.5mm. The MTV experiment uses a cylindrical drift chamber (CDC) as the main electron-tracking detector. The barrel-type trigger counter is placed inside the CDC to generate a trigger signal using 1mm thick, 300mm long thin plastic scintillation counters. Detection efficiency and light attenuation compared with conventional wrapping materials are studied.
The MTV experiment (
M
ott Polarimetry for
T
-
V
iolation Experiment) is running at TRIUMF, to search for a large
T
-violating transverse electron-polarization in polarized
8
Li
β
-decay. We aim at ...reaching precision of 10
−4
for the
R
-correlation, which is defined as a
T
-violating triple vector correlation in the
β
-decay rate function. A Mott polarimeter system using a CDC (
C
ylindrical
D
rift
C
hamber) is used to measure the left-right scattering asymmetry in the Mott scattering from a thin metal foil. In the present study, we aim to discuss systematic effects in Mott polarimetry using the CDC.
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