The rad~ative decay K + --t p + v y has been studied by a high-resolution magnetic spectrometer combined with a NaI(T1) photon detector system. The momentum spectrum of muon from this decay mode was measured in the region 214.5 < p , <231.5 MeV/c. The observed partial decay rate of the rad~ative decay in this reg~on agreed with the QED calculation within the error of 3%. The structure-dependent components of the decay were studied and new values of the form factors were obtained as 1 FV+FA / (,&fK <0.23, -2.5 <
We have studied the local structure of GeSi nanocrystals embedded in SiO2 prepared by co-sputtering of Ge, Si, and SiO2 targets onto a Si(100) substrate. From Raman scattering, we conclude that the formation of the isotropic crystalline Ge phase starts at about 800 °C followed by the formation of a GeSi phase at higher temperatures. The formed nanocrystals, whose size depends on the annealing temperature, are randomly oriented. The local structure of the nanocrystals has been studied by x-ray absorption fine structure spectroscopy. They are found to consist of a relaxed Ge core with a typical diameter of ∼4 nm and the Ge–Ge bond length of 2.45 Å and of a GeSi outer shell, the Ge–Si bond length being 2.39 Å. The average composition of the grown nanocrystals is estimated to be Ge0.75Si0.25.
The longitudinal polarization of the muon emitted in the decay K + -+ p + v was measured to search for right-handed weak currents in a strangeness-changing process. The 236-MeV/c muons from the decay of stopped K f were identified and were collected by a magnetic spectrometer. The muons were then slowed down in a carbon degrader and were brought to rest in an aluminum target. The muon spins were precessed by a 220-G transverse field, and a muon-spin-rotation technique was employed to measure the muon-spin polarization. The polarization was determined to be -0.970f 0.047, which is consistent with the V -A hypothesis.
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