In a study of photoproduction at photon energies between 0.3 and 5.8 GeV in a hydrogen bubble chamber, approximately 1.7 million pictures containing about 31 000 events with three or more outgoing charged particles were analyzed. This is the second of two final reports on this experiment. Distributions of effective masses are given for the reactions yp -> N3ir, N4TT, N57r. Cross sections for the production of A (1236) and p via yp -> Ap, A2ir, A37r, A47r, Nirp, and N2irp and of various other reactions are reported. From the reaction yp -» A ++ p~, an upper limit for the radiative decay width of p~, r(p~ -• > ir~~y) <0.24 MeV, is obtained (90% confidence). For the four-pion decay mode of the p°, an upper limit of r (p° -> 7r + 7r + 7r~7r~)/T(p° -» ir + ir~) <0.0015 is found (90% confidence). The photoproduction of strange particles is discussed and cross sections for yp -> AK + , 2K, AKTT, XKTT, and KK-KTV are presented. Production of 2 (1385) was observed.
Durch Beobachtung der Zahl der Kern Zertrümmerungen in photographischen Emulsionen wird die Absorption der Nukleonenkomponente der kosmischen Strahlung in Luft zwischen Seehöhe und 3774 m untersucht.
Three hundred and seventeen heavy-nuclei and 175 a-particle interactions of more than 7 Bev/nucleon have been found in a systematic way and analyzed. We obtained average values and fluctuations of the individual values for the energy of heavy nuclei as measured by the opening angle of their fragments by comparing with the energy found by scattering measurements. At an average energy of 10 Bev/nucleon and 40 Bev/nucleon the average number of charged mesons produced by a-particle interactions with emulsion nuclei was found to be 4.6 and 8.2, respectively. About one half of the nucleons of the a particle participate in the collision. The meson multiplicities per participating nucleon agree for proton and a-particle collisions at 10 Bev/nucleon.We measured the angular distribution of the shower particles emitted from the interactions. We calculated the energy of the interactions from the angular distribution by using the median angle formula or equivalent formulas, based on the "meson spectrum independent ,, approximation. These methods overestimate the true primary energy on the average by a factor of 2 (for interactions with less than 5 heavily ionizing prongs). This is due to the relatively large proportion of slow mesons in the cm. system. The distribution of primary energy as obtained by this method around the true value is shown for two groups having average energies of 10 Bev/nucleon and 40 Bev/nucleon. Equivalent results are given for the heavy-nuclei interactions.The average number of mesons produced in collisions between heavy nuclei and emulsion nuclei at an average energy of 20 Bev/ nucleon is given. It increases with the charge of the incident nucleus in agreement with a crude geometrical model.
Nuclear interactions of protons, neutrons, a particles, and heavier nuclei of average energy 250 Bev/nuc were studied in nuclear emulsion. The source of these particles were fragmentations of heavy primary nuclei of the cosmic radiation. Their energy was determined from multiple scattering measurements. The interaction mean free path for protons is 41 ±10 cm, for a particles 27±7 cm. The mean free path shows no significant change compared with measurements at lower energies. The mean number of shower particles {n s ) depends appreciably on the mass of the target nucleus. Our best estimate for nucleon-nucleon collisions at 250 Bev is (»,) = 8.8=1= 1.9. A detailed comparison of the estimate of the primary energy obtained from the angular distribution of shower particles with the true primary energy is carried out. The angular distribution of the shower particles will, in an individual case, give a quite unreliable value for the primary energy. In the average, the angular distribution method will overestimate the true primary energy by a factor of 1.3 for interactions with a number of heavy prongs iVfc<5. If Nh>S, the angular distribution will underestimate the true energy in the average by a factor of 1.8. The angular distributions can be transformed into a system in which they are symmetric. This is even true for collisions with heavy target nuclei (Nh>S). The results for alpha particle and heavy nucleus collisions are quite similar.The inelasticity for the proton and neutron interactions shows large fluctuations for individual events. It depends weakly on the number of shower particles and on the mass of the target nucleus. Its mean value is 50%. The mean value for the alphaparticle collisions is 22%.
Das Spek~rum der yon einer (Ra ~r + Be)-Quelle ausgesandten schnellen Neutronen wird hinter 7 cm Pb dutch Beobachtung der yon ihnen in einer photographischen Schicht ausgel6sten RiiekstoBprotonen untersucht. Durch Vergleich mit dem PrimSxspektrum werden Riickschliisse auf die unelastische Streuung in Pb gezogen. * "q'or, getragen auf der Tagung der Deutschen Physikalischen Gesetlschait in der Britischen Zone in Hamburg am 22. April 1949.
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