5 research outputs found
Phase Variation of Hadronic Amplitudes
The phase variation with angle of hadronic amplitudes is studied with a view
to understanding the underlying physical quantities which control it and how
well it can be determined in free space. We find that unitarity forces a
moderately accurate determination of the phase in standard amplitude analyses
but that the nucleon-nucleon analyses done to date do not give the phase
variation needed to achieve a good representation of the data in multiple
scattering calculations. Models are examined which suggest its behavior near
forward angles is related to the radii of the real and absorptive parts of the
interaction. The dependence of this phase on model parameters is such that if
these radii are modified in the nuclear medium (in combination with the change
due to the shift in energy of the effective amplitude in the medium) then the
larger magnitudes of the phase needed to fit the data might be attainable, but
only for negative values of the phase variation parameter
Energy dependence of pion double charge exchange
The energy dependence of forward angle pion double charge exchange is calculated in the energy range of 0–250 MeV. The most striking feature is a peak around 40 MeV which is in excellent agreement with the data when distorted waves obtained from a realistic optical model are used. Two possible short-range corrections to the reaction mechanism are addressed
Pion double charge exchange on 4He
The doubly differential cross sections for the He
reaction were calculated using both a two-nucleon sequential single charge
exchange model and an intranuclear cascade code. Final state interactions
between the two final protons which were the initial neutrons were included in
both methods. At incident pion energies of 240 and 270 MeV the low-energy peak
observed experimentally in the energy spectrum of the final pions can be
understood only if the contribution of pion production is included. The
calculated cross sections are compared with data.Comment: 25 pages, 9 figure