Nuclear Physics B90 (1975) 296-306 © North-Holland Pubhshlng Company ISOTENSORn-~PHASE SHIFTS BELOW THE p MASS R.D. BAKER* Cavendtsh Laboratory, Cambridge, England Received 2 October 1974 (Rewsed 29 January 1975) We present the results of a Chew-Low extrapolation of the reaction 7r+p ~ *r+ at plon beam momenta 1 4 and 1 5 GeV/e. By extrapolating the *r+*r÷ ~ *r+lr + cross sectmn and the asymmetry of the *r-,r angular distribution, lsotensor (1 = 2) S and D wave determined at energies up to the p mass. Our S wave was greater than prevaous e and our D wave roughly constant at a value of -1~ ° , much greater than the Lovela Venezmno prediction 1. Introduction This paper presents the results of a Chew-Low extrapolation performed on the final state Ir+Tr+n Dipion production from the beam proceeds purely by lsovector exchange, and is therefore free from 6o 0 exchange, which is believed to be large be- low the p mass m reactions where it is possible, as m, say, ~r-p ~ ~r-lr°p. In such reactions where p produchon is possible, most of the events will be m the p peak, whereas our events are more evenly spread over all available 7r-Tr energies while our low beam momentum concentrates the events into the small energy range 4 - 4 0 ~2 (fig. 2a). Only two partial waves contribute m this energy range, the S and D lsotensor (S 2 and D2) waves, so that the angular distribution gives a good estimate of D 2. There are still few estimates of this wave. There is little intrinsic mterest m the I = 2 channel, however, the lr-lr system is so interlocked by crossing, analytlcity and umtanty, that almost any rehable piece of data is of value, especially for low-energy self-consistency calculations, such as those using the Roy equation. Ref. [ 1 ] remark that accurate low energy I = 2 data would constrain the 1 = 0 S-wave, in their analysis. * Present address" Rutherford Laboratory, Chilton, Dldcot, Oxon