No abstract

low pion-emission angles, effort also will be expended to determine 7rV?7 + ratios closer to the forward direction. We intend to provide cross sections both for additional doubly even nuclei and for targets with N^Z.In the latter nuclei the contributions of isovector and isotensor components of the spin-isospin correlation functions can be investigated. *Supported by the Deutsche Forschungsgemeinschaft. i J. Amann et al. 9 Phys. Rev. Lett. ^5, 426 (1975); H. Dollard et al. 9The charge-exchange reaction (77", 77 0 ) for stopped negative pions is known 1 " 6 to occur for only two targets, X H and 3 He, although it is energetically allowed for most medium-heavy-mass nuclei. Several searches for the reaction T\~d-~Tpnn have been conducted using either counters 4,5 or internal conversion in a bubble chamber 6 to detect the 77 0 decay y's, and upper limits of 2xl0" 3 and 1.2 xlO" 3 , respectively, for the branching ratio 9 E 0 Borie, H. Chandra, and D. Drechsel, Nucl. Phys 0 A226, 58 (1974). 10

No abstract

A new measurement of the -n^ev branching ratio yields T{n-*ev + n^evy)/T{'K-~\xv + 7T-fivy) = (1.218± 0.014)x 10~4. The measured value is in good agreement with the standard-model prediction incorporating electron-muon universality.