The Production of Positive Pions by 341-Mev Protons on Protons

Abstract

The production of positive pions by protons on protons has been studied at 00, 350 and 580 to the beam of 341 Mev protons produced by the Berkeley ayncbro-cyclotran. In the collision of two protons, two reactions are possible which lead to a w+_me eon: (1) P + p1+ + D and (2)? + + N +P. The experimental results at 00 show an energy spectrum from 0 to 70 Mev which is farily flat except for a large peak at the high energy end. The flat portion of the spectrum can only be due to reactIon (2). A comparison of the shape of the peak with the results of the phenomenological theory of Brueckner and Watson shows that the peak is due solely to reaction (1). This fact, together with a measurement of the energy of the beam and of the energy of the pions from reaction (1), gives the value 275.1±2. 5 electron masses for the mass of the positive pion. The angular distribution in the center of mass system for reaction (1) as obtained from the data at the above three angles, is 3. 3*1. 2 1.11±. 06 + cos 2 Q]. 10 29 cm2 st erad.-1 and the total cross section for reaction (1) is 1. 8*0. 6 10 28cm2. These results have been compared with the results obtained by Durbin. Loar, and Steinberger and by Clark, Roberts, and Wilson on the inverse reaction, it + D.-P + P. UsIng the theorem of detailed balancing, these experiments lead to the value zero for the spin of the positive pion with good certainty.

ON THE LOW-ENERGY PION-NUCLEON INTERACTION (thesis)

“…This is closely analogous to the reaction p +p-• +d,i n which the proton and neutron have low relative energy and thus interact to form the deuteron. This case has been studied in considerable detail by Brueckner and Watsonl theoretically, and by Cartwright,Richman,3 Whitehead and Wilcox experimentally. At the appropriate pion energy for deuteron formation, they find a susbtantial increase in the pion-production cross section which they attribute to the strong attractive interaction of the final nucleons.…”

Pion-Muon Asymmetry Revisited

“…If the π -μ asymmetry results [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] are not interpreted as evidence of non-zero pion spin, then they are not in conflict with the many experiments showing that the pion has spin 0 [21,[29][30][31][34][35][36]. Furthermore, an experiment in which the asymmetry axis is modified in a controlled manner has been proposed.…”

Scattering of Pions by Hydrogen at 165 Mev

“…The same choice has provided the basis for a successful interpretation of a number of the features of the process of pion production by nucleons as well as by gamma rays. Thus, Brueckner and Watson 18 have pointed out that the angular distribution observed 19 for the reaction p+ p~^> 7r + -f-d is not very different from the form 0.3+cos 2 x which it would have with the p% state of the pion-nucleon system dominant. Subsequently, a more detailed study by Rosenfeld 20 and a general review by Gell-Mann and Watson 14 have reaffirmed this point of view.…”