a b s t r a c tThe PIENU experiment at TRIUMF is aimed at a measurement of the branching ratiowith precision o 0:1%. Incident pions, delivered at the rate of 60 kHz with momentum 75 MeV/c, were degraded and stopped in a plastic scintillator target. Pions and their decay product positrons were detected with plastic scintillators and tracked with multiwire proportional chambers and silicon strip detectors. The energies of the positrons were measured in a spectrometer consisting of a large NaI(Tℓ) crystal surrounded by an array of pure CsI crystals. This paper provides a description of the PIENU experimental apparatus and its performance in pursuit of R e=μ .
Low-lying states below 500keV excitation in 112In have been investigated via the 112Cd(p, nT) reaction. New levels have been established at Ex=206.5 keV and 456.1 keV from the measured y-ray excitation functions, 7-7 coincidences and the precision measurements of the (p, n) threshold energy of the ground state and of the 206.5 keV state of ~12In. Spins and parities of the 206.5 keV state (2 +) and the 456.1 keV state (3 +) and multipolarities and mixing ratios of the deexcitation y-rays have been determined from the angular distributions and linear polarizations of the deexcitation g-rays as well as the excitation functions of the residual levels. Possible configurations of the newly-found levels are discussed. Half-lives of two states have been remeasured: T~= 15.2+0.1 min for the ground state and ~=20.9 -+0.1 min for the 156.4 keV (4 +) state. The ground state Qvalue for the 112Cd(p ' n)112in reaction has been measured to be -3.376-+ 0.006 MeV.
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