RICHARD FRIEDBERGSince the parameter b in (IS) approaches 1 as the electron energy approaches its maximum TFo-w" 2 /2m M , the relative sensitivity of /* decay to a and m v is different from that of processes (3) and (4). To take the example of the last paragraph but one, if a-0 and 7w"=1.6 MeV, the parameter b would affect both the energy spectrum and the asymmetry, for electron energies near the maximum, by an amount that might be observed by an improvement of existing measurements. But if 0=0.02 and m"=0, the parameter a 2 in (15) would be quite negligible. Thus, an improved measurement of the tail of the electron spectrum in ju decay might be combined with a measurement of the branching ratios for (3) and (4) to give an estimate of both a and m v .The preceding considerations are theoretical. In the immediate future, however, there is little hope of observing reactions (3) and (4) unless the branching ratio Rz/Ri is at the least 0.01. Such a large effect could not be produced by m v alone and could only be interpreted as evidence that a 2 >0. Indeed, it is known from the energy-momentum balance in ir-y. decay 6 that 6 W.

We report the nleasurement of the polarization in the reaction rir-+p -+ 7.ro'fz a t an incident-pion kinetic energy (lab) of 310 MeV and at an angle of 30° in the c.m. system. The polarization v a s obtained from measurements of the left-right asymmetry in the scattering of the neutrons from liquid helium a t lab-scattering angles of 75" and 125". The measured polarization is 0.24rt0.07.

A phase-shift analysis of T + -p and tC-p elastic scattering at 310 MeV has been performed. The data include differential and total cross section and recoil-proton polarization data for both T + -p and iT-p elastic scattering, as well as differential cross-section data for charge-exchange scattering. Inclusion of d waves was necessary to attain an adequate fit to the data; in the case of ir~-p differential cross section, the best fit included / waves. A general phase-shift search using s, p, and d waves was carried out; a single solution was obtained that adequately fit all the available data. The most notable characteristics of this solution are isotopic-spin 3/2 phase shifts similar to those obtained in a previous analysis of the w + -p data and a relatively large JDI, B phase shift equal to approximately 15 deg. Errors on the isotopic-spin 1/2 phase shifts of this solution range from 0.3 to 0.9 deg. The isotopic-spin 3/2 phase-shift errors are similar to those obtained previously. Because the r~-p differential cross section data indicated a possible need for / waves, and since the only satisfactory spd solution displayed a large d-wave phase shift in the isotopic-spin 1/2 state, the analysis was extended to include / waves. The result of allowing / waves was to increase the errors on each of the phase shifts (up to about 2 deg), and also to introduce two new solutions, neither of which can be ruled out statistically. These new solutions are similar to the