Pion-Proton Resonance Scattering Near 900 Mev

Abstract

would be about one millibarn if the scattering were largely inelastic or elastic and isotropic. The effect otherwise could be much larger depending on the real parts of the neutron and proton forward scattering amplitudes, which are unknown.From the attenuation of the E^O target we obtain for the total K + -oxygen cross section (for absorption and diffraction scattering) at 0.69 Bev a value of 270 ±20 mb which is 90% of geometric.The K -proton total cross section was measured at 0.96 and 1.23 Bev with the result 36 ± 5 and 44 ± 5 mb, respectively. From the decay in flight we obtained the lifetime r^+ = (1.21 ±0.06) xlO" 8 sec in good agreement with previous measurements on stopped K's. By this method we measured the ratio of K" to K+ lifetime directly and got T#-/T# + = 0.97 ±0.09.We note the following: (a) The JC + -proton total cross section reaches a maximum of 4ir(fi/m K c) 2 or about 7r(S/2m ff c) 2 at P Q m * -m^c; i.e., a total cm. kinetic energy (b) The IT -proton and K -neutron total cross sections are about the same in this energy range; the K" -proton cross section is roughly twice as large.(c) The contribution to the dispersion relation as evaluated by Matthews and Salam 5 is not negligible in the total energy range above 2m g as they assumed tentatively. Assuming from our results that o(K~) -o(K+) in the energy range 2 to 5 mj{ is 25 mb, we find a contribution of -0.5 in their units.The results of a new measurement of the 77"proton and 7r + -proton total cross sections and acknowledgments are given in an accompanying Letter. *

The Way We Were: Bubble Chamber Pictures, Pion-Nucleon Interactions and Polology

“…15 12 These experiments had been independently performed at the Cosmotron (Crittenden et al (12) ) and at the Berkeley Bevatron (Burrowes et al (13) ). 13 V. Alles-Borelli et al (14) . Emma Perez Ferreira, on leave from the Comisión Nacional de Energía Atómica, Rep. Argentina, had in the meanwhile joined the group.…”

“…14 In the meanwhile Franco Selleri (hereafter Franco) had come into play: he had collaborated as a theoretician to the last-mentioned research, calculating the spectra for the incident pion kinetic energy of 960 MeV. 15 12 These experiments had been independently performed at the Cosmotron (Crittenden et al (12) ) and at the Berkeley Bevatron (Burrowes et al (13) ). 13 V. Alles-Borelli et al (14) .…”

Scattering of 3.7-25 Mev Positive Pions by Hydrogen

“…Although it is possible to solve for all three phase shifts simultaneously, at these low energies the contribution of the p-w&ve to the cross section is very small. We therefore assume the p-w&ve phase shifts known from higher energy experiments 9 to be a 88 =0.21(V and a 8 i= -0.042 7f.…”

“…At 24 Mev, the highest point covered by this experiment, our experimental values overlap and are in agreement with counter measurements. 9 II. METHOD…”

Nuclear Interactions in Carbon Produced by Cosmic Rays with Energies between1010and1012ev

“…1, and has been described previously. 6,7 The experiment was done at sea level. The cloud chamber was in a magnetic field of about 8000 gauss and was filled with a mixture of 16 cm Hg of argon and 16 cm Hg of helium, together with a mixture of ethyl alcohol and water in proportion 3:2 by volume, which produced a vapor pressure of about 4.5 cm Hg.…”