Search

The conserved-vector-current hypothesis, together with measured nuclear-beta-decay rates, predicts a value of the rate for the decay ..pi../sup +/..--> pi../sup 0/e/sup +/..nu.. of 0.4027 +- 0.0018 s/sup -1/. With use of a decay-in-flight technique the authors have made the most precise measurement to date of this rate, obtaining the value 0.398 +- 0.015 s/sup -1/, in good agreement with the prediction.

A search has been performed for the muon-number--violating decay ..mu -->..e/sup +/e/sup +/e/sup -/. No candidate event has been found, the result yielding an upper limit for the branching ratio of B/sub mu3e/ ..e/sup +/e/sup +/e/sup -/..nu../sub e/nu-bar/sub ..mu../ events, eleven such events were observed. They agree in number and spectra with expectations based on standard electroweak theory.

We have analyzed 25 000 ${K}_{e3}$ decays, reconstructed to the center of mass by measurement of the ${{K}_{L}}^{0}$ momentum from time of flight and measurement of the $\ensuremath{\pi}$ and $e$ momenta with a spark-chamber-magnet spectrometer. Using the linear parametrization of the vector form factor ${f}_{+}({q}^{2})=1+{\ensuremath{\lambda}}_{+}(\frac{{q}^{2}}{{{m}_{\ensuremath{\pi}}}^{2}})$ we find ${\ensuremath{\lambda}}_{+}=0.0270\ifmmode\pm\else\textpm\fi{}0.0028$. Upper limits for the scalar (${f}_{s}$) and tensor (${f}_{t}$) form factors at the 68% confidence level are $\frac{{f}_{s}}{{f}_{+}}l0.04$, $\frac{{f}_{t}}{{f}_{+}}l0.23$, corresponding to intensity ratios $\frac{{I}_{s}}{{I}_{v}}=0.3%$ and $\frac{{I}_{t}}{{I}_{v}}l0.4%$.

The inclusive cross sections, measured up to large values of effective mass ($\ensuremath{\equiv}\frac{{q}^{2}}{2\ensuremath{\nu}}$), are well fitted by $\frac{d\ensuremath{\sigma}}{{d}^{3}p}={B}_{x}\mathrm{exp}(\ensuremath{-}\frac{{\ensuremath{\alpha}}_{x}{p}^{2}}{2{m}_{x}})$. Values of ${B}_{x}$ and ${\ensuremath{\alpha}}_{x}$ are given for Be, C, Cu, and Ta at the incident proton energy of 600 MeV and for Ag, Ta, and Pt at 800 MeV. Extremely large $\frac{d}{p}$ and $\frac{t}{p}$ ratios and large $A$ and ${q}^{2}$ dependences of the relative cross sections are observed.

This Letter reports a new experimental search for the family-number-nonconserving decay ..mu../sup +/ ..-->.. e/sup +/..gamma... There is no evidence for the presence of this decay mode. The upper limit for the branching ratio is GAMMA(..mu.. ..-->.. e..gamma..)/GAMMA(..mu.. ..-->.. enu anti nu) < 4.9 x 10/sup -11/ (90% C.L.). 13 refs., 3 figs.

A new search for three-photon decays of the neutral pion has been made. No signal in excess of background was observed. The upper limit for the ..pi../sup 0/ ..-->.. 3..gamma.. branching ratio is 3.8 x 10/sup -7/ (90% confidence level).

A new experimental search with the Crystal Box detector shows no evidence for the lepton-family-number--nonconserving decay ..mu../sup +/..-->..e/sup +/..gamma gamma... This corresponds to an upper limit for the branching ratio of GAMMA(..mu -->..e..gamma gamma..)/GAMMA(..mu -->..e..nu..nu-bar)