Gamma-neutrino angular correlation in muon capture on 28Si

A measurement has been made of the angular correlation of the neutrino with a specific nuclear de-excitation γ-ray following exclusive muon capture on 28Si. This correlation is sensitive to the induced weak pseudoscalar coupling gp, and is relatively insensitive to the details of the nuclear structure. The correlation is observed via the Doppler-broadened lineshape of the γ which is measured using Compton-suppressed Ge detectors. Significant background suppresion is achieved through the use of a coincidence technique wherein the γ-ray of interest is open-quote tagged close-quote using a subsequent γ-ray in the cascade, which is detected in an array of NaI scintillators. A determination of gp to about 10% precision is anticipated