Muon Capture in(pμd)+Molecules

Abstract

The ${(p\ensuremath{\mu}d)}^{+}$ molecules and $\ensuremath{\mu}\ensuremath{-}{\mathrm{He}}^{3}$ atoms formed in liquid hydrogen were used to detect neutrons from muon capture by deuterons and from muon capture by ${\mathrm{He}}^{3}$. In the experiment, a purified muon beam was stopped in a target containing ultra-pure liquid hydrogen with 0.32% deuterium added. Neutron-gamma-ray discriminating detectors and oscilloscope photography enabled us to measure the time distribution of neutrons from the following rare muon-capture processes: ${\ensuremath{\mu}}^{\ensuremath{-}}+d\ensuremath{\rightarrow}\ensuremath{\nu}+2n,$ ${{\ensuremath{\mu}}^{\ensuremath{-}}+{\mathrm{He}}^{3},\ensuremath{\rightarrow}\ensuremath{\nu}+n+d}{\ensuremath{\rightarrow}\ensuremath{\nu}+2n+p}$. Knowledge of the time distributions of the various ${(p\ensuremath{\mu}d)}^{+}$ hyperfine states and of the $\ensuremath{\mu}\ensuremath{-}{\mathrm{He}}^{3}$ atoms was used to unravel the various muon-capture rates of interest. Converted to the $\ensuremath{\mu}d$ atom case, the measured rate gives 365\ifmmode\pm\else\textpm\fi{}96 ${\mathrm{sec}}^{\ensuremath{-}1}$ for muon capture from the doublet state of $\ensuremath{\mu}d$. This is to be compared with the theoretical rate of 334 ${\mathrm{sec}}^{\ensuremath{-}1}$ predicted by the current phenomenological muon-capture theory; and it provides the simplest verification of the Pauli exclusion-principle effect in muon capture. The neutron rate from muon capture by ${\mathrm{He}}^{3}$ was determined to be (1.20\ifmmode\pm\else\textpm\fi{}0.17)\ifmmode\times\else\texttimes\fi{}${10}^{3}$ ${\mathrm{sec}}^{\ensuremath{-}1}$.