On the imaginary part of the nucleon-nucleus potential

Cross section data for interactions of nucleons, antinucleons, mesons (K), and mesons ( pi ) are compiled and discussed. At high energies, specific features common to particles of different kinds exist. Information on phenomena occurring in the region of very small space-time scales may be obtained. Most of the data is obtained from experiments using accelerators in which large particle- beam densities facilitate precision measurements. Weak neutrino reactions at high energies are discussed. (L.N.N.)

Cross Sections for Elementary Particle Interactions

The complex potential for neutrons in an infinite nuclear medium is computed in a perturbation calculation up to the second order, using for the nucleon-nucleon interaction a regular potential which fits the low energy two-body data. It is shown that it is possible to fit simultaneously the real and the imaginary part of the optical potential and the binding energy of the nuclear matter at normal density. Some arguments for the convergence of the theory are given.

On the optical model for nuclear reactions

On the imaginary optical potential

Ilford G5 emulsions have been exposed to a 925 mev beam from the Birmingham proton synchroton. Sixty-five examples of the elastic scattering of protons by free protons in the emulsion have been found in 1539 metres of track. After removal of events having azimuthal angles ψ>45° where ψ is the angle between the plane of the two secondary particles and the plane of the emulsion, the remaining 44 events yielded a total elastic cross section of 17±3mb. The angular distribution of all the events shows a strong forward peak in the centre of mass system. The shape of this distribution has been compared with the predictions of a simple optical model and a value of (0·9±0·1) × 10−13 cm has been found for the interaction radius of the proton. The results are compared with other experimental work.

The elastic scattering of protons by protons at 925 MeV

Si riferisce sul decadimento del Cd109 per cattura elettronica orbitale. Il rapportoP

 L
 /P

 K
 tra la probabilita di disintegrazione per catturaL e quella per catturaK viene determinato misurando con un contatore proporzionale l’intensita delle radiazioniLX eKX. Si ottiene:P

 L
 /P

 K
 =0,32±0,04. Una conferma di questo risultato viene ottenuta misurando le intensita delle radiazioniKX e γ con uno spettrometro a scintillazione ad un cristallo. Questo metodo fornisce il valore:P

 L
 /P

 K
 ≊0,29. Utilizzando la teoria di Marshak sul decadimento per cattura elettronica, si ha per l’energia della transizione:E
0=67
 −3
 +8
 keV.

L. Beretta

Papers

Sezioni d’urto elastico protone-protone e neutrone-protone