Proton-Proton Scattering at 5.77 Mev

Absolute differential scattering cross sections for proton-proton scattering at laboratory energies of 5.77 and 5.86 Mev (±1 percent) have been obtained with an accuracy of about one percent at many angles (23° to 110° c.m.) by two independent experiments, one employing nuclear emulsion plates as detectors and the other employing proportional counters. Reduced to the same energy, the average indicated $S$-wave nuclear phase shift is in excellent agreement with other data for this energy region. However, at small scattering angles, important for determining a $P$-wave phase shift, the measured cross sections differed originally by 3 to 5 percent, the nuclear emulsions method indicating a $P$-wave shift of -0.08±0.05 degree, and the original counter data indicating -0.34±0.05 degree. After the beam collimation was improved and the energy spectrum of the incident proton beam was examined, check runs with the counters at six scattering angles failed to indicate the large $P$-wave effect, giving -0.08±0.07 degree, in agreement with the emulsion data. It therefore appears likely that the $P$-wave shift at this energy is small (less than 0.1 degree) and negative, in agreement with other determinations in this energy region.