Search Results (13 total)

A baryon resonance of mass 1667±5 MeV/c² is produced in the reaction π^-+d→pp+π^-+π^- at 2.26 GeV/c in a non-t-channel process. Its properties and production mechanism are discussed. The branching ratio for its decay was found to be Δπ / Nπ<0.11.

We have found that the forward-backward asymmetry exhibits a very slight Δ² dependence affording a model-independent extrapolation. When the above method is complemented with a factorization-model analysis, a unique set of I=0 S-wave pion-pion phase shifts is obtained, modulo π. New tests of the absorption model have been made.

Evidence is presented to confirm the existence of an I=5 / 2 baryon resonance at 1640 MeV/c². The resonance is observed in the reaction π^-d→pnπ^-π^-π⁺ at 2.6 GeV/c² and is found to decay into nπ^-π^- possibly via Δ^-(1236)π^-. It is shown that the observed peak cannot be due to kinematical effects such as those responsible for the I=5 / 2 enhancement at ≃1580 MeV/c² observed earlier.

The cross sections for π^-π⁰ and π^-π⁺ elastic scattering, and the I=0 s-wave and I=1 p-wave phase shifts, δ₀⁰ and δ₁, are calculated for 400<M_ππ<900 MeV using a Chew-Low extrapolation. The extrapolation information permits resolving a fourfold ambiguity which has been present in other attempts to determine δ₀⁰ from the reaction π^-p→π⁺π^-n. The result for δ₀⁰ is consistent with a curve which increases through 90° around M_ππ=720. The ρ width obtained from the extrapolated p-wave amplitude is 105 ± 15 MeV.

Further evidence is presented for the existence of heavy nuclei as components of the primary cosmic radiation. Preliminary results are given for the distribution in atomic numbers of these components. Lower limits of the energies of the particles on entrance into the atmosphere are calculated. These are, in general, above the cut-off imposed by the earth's magnetic field. The mean free path for nuclear collisions is of the order of 14 cm of photographic emulsion. This is longer than that expected from the geometrical cross section and may indicate velocity dependence of nuclear forces. An example of a track that stops in emulsion is shown. This particle gives further evidence for the nuclear character of the rays, because as it slows down it captures planetary electrons and decreases its rate of energy loss. An approximate value of the hydrogen-helium ratio of 4 is reported.