Search

We have studied correlations between two ${\ensuremath{\pi}}^{0}'\mathrm{s}$ produced at the CERN intersecting storage rings, utilizing detectors with large azimuthal acceptance. We find that the previously observed enhancement of two ${\ensuremath{\pi}}^{0}'\mathrm{s}$ produced at azimuthal difference near 180\ifmmode^\circ\else\textdegree\fi{} can be made to vanish when certain kinematic effects are removed. However, we observe aligned configurations above 8 GeV of transverse energy unexplained by such kinematic effects.

Correlations of two ${\ensuremath{\pi}}^{0}$ mesons with transverse momenta ${p}_{T}$ up to 13 GeV/c have been measured with large azimuthal acceptance. Results for cross sections, ${p}_{\mathrm{out}}$, and $z$ distributions are compared in detail with models based on two-constituent scattering and fragmentation. The width of the constituent transverse-momentum Gaussian distribution would have to be doubled to match that from experiments with ${p}_{T}$ below 5 GeV/c. A more likely explanation is the presence of processes with more than two constituents in the final state.

Negative muons from the Carnegie Tech synchrocyclotron were stopped in the following targets: separated isotopes of lithium (${\mathrm{Li}}^{6}$ and ${\mathrm{Li}}^{7}$) and boron (${\mathrm{B}}^{10}$ and ${\mathrm{B}}^{11}$), and natural beryllium, carbon, nitrogen, and oxygen. From an analysis of the resulting time spectrum of the decay electrons, the negative-muon lifetime in each of these substances was obtained. From a separate measurement of the ${\ensuremath{\mu}}^{+}$ lifetime, (2.202\ifmmode\pm\else\textpm\fi{}0.003) \ensuremath{\mu}sec, the capture rates in the above elements were determined. They are (in units of ${10}^{5}$/sec); ${\ensuremath{\lambda}}_{\mathrm{cap}}({\mathrm{Li}}^{6})=0.061\ifmmode\pm\else\textpm\fi{}0.014$, ${\ensuremath{\lambda}}_{\mathrm{cap}}({\mathrm{Li}}^{7})=0.018\ifmmode\pm\else\textpm\fi{}0.014$, ${\ensuremath{\lambda}}_{\mathrm{cap}}({\mathrm{B}}^{10})=0.265\ifmmode\pm\else\textpm\fi{}0.015$, ${\ensuremath{\lambda}}_{\mathrm{cap}}({\mathrm{B}}^{11})=0.218\ifmmode\pm\else\textpm\fi{}0.016$, ${\ensuremath{\lambda}}_{\mathrm{cap}}(\mathrm{Be})=0.10\ifmmode\pm\else\textpm\fi{}0.02$, ${\ensuremath{\lambda}}_{\mathrm{cap}}(\mathrm{C})=0.397\ifmmode\pm\else\textpm\fi{}0.013$, ${\ensuremath{\lambda}}_{\mathrm{cap}}(\mathrm{N})=0.65\ifmmode\pm\else\textpm\fi{}0.04$, and ${\ensuremath{\lambda}}_{\mathrm{cap}}(\mathrm{O})=0.98\ifmmode\pm\else\textpm\fi{}0.03$.

Serious difficulties from extinction are shown to exist in the interpretation of past experiments on $\ensuremath{\gamma}$ rays from moving sources. We have measured the relative speed of the two $\ensuremath{\gamma}$ rays emitted forward and backward by a ${\ensuremath{\pi}}^{0}$ meson decaying in flight. The velocity of the neutral pions, which were produced in the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}+p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}+n$, was $v=0.2c$. We have compared our results with what would have been expected, taking account of extinction, on the assumption that the initial photon velocities were $c+v$ and $c\ensuremath{-}v$. The results were in complete disagreement with this assumption.