Determination of proton size from pi sup + p and pi sup - p scattering at T subpi sub sup+- = 277-640 MeV

The pion-nucleon interaction above the DELTA (1232) resonance and in the region of low-lying pion-nucleon resonances is studied. pi sup+-p elastic scattering at T subpi sub sup+-1% = 277 - 640 MeV characterized by diffraction maxima and minima has been analyzed through the strong absorption model due to Frahn and Venter. The proton radius is determined from the best fit values of the cut-off angular momentum to be 0.85 fm with a spread of 0.15 fm. The higher energy pions scan a lower value while the lower energy pions yield a higher value for the size of the proton. The energy averaged radius of the proton size of 0.85 fm obtained in the present analysis is in excellent agreement with proton charge radius of 0.86 fm quoted in the literature.