Analysis of inelastic interactions of K⁺-mesons with emulsion nuclei (40 ÷ 150 MeV)

Summary

212.5 m of K⁺ track have been followed in an unbiassed way in the energy interval from 40 to 150 MeV. The events found have been classified as follows: 1) 8 K-H interactions; 2) 184 inelastic scatterings (excluding the charge exchange); 3) 23 charge exchange. All these events have been divided into four energy intervals (see Table IV). In the present work, data on the K⁺-nucleus and K⁺-nucleon inelastic interactions have been given. For the K⁺-nucleus interactions we give: (i) The variation of the total cross-section with the primary energy; (ii) The angular and energy loss distributions and their correlation; (iii) Further support for a nuclear repulsive potential. Starting from the inelastic events, an analysis has been made to find the elementary K-nucleon cross sections. Table VI summarizes the procedure followed in this analysis. The peculiar feature of the analysis consists in taking into account the correlation between the angular and energy loss distributions. We have chosen with a maximum likelihood method the angular distribution in the centre of mass system which reproduces the observed distributions for inelastic events. Particular care was taken to ensure that the separation between elastic and inelastic events would not alter the essential results of the analysis. We have also made some tests on the internal consistence of our analysis. The total and angular K-free nucleon and K-free neutron cross-sections (for scattering as well as for charge exchange) have been deduced with this analysis. Our values for elementary cross-sections have been compared with those estimated by other authors. Finally, we have evaluated the scattering amplitudes and the relative weight of theT = 1 andT = 0 states.

Riassunto

Sono stati osservati 212.5 m di traccia di K⁺ nell’intervallo energetico 40 ÷ 150 MeV. Sono riportati i seguenti dati: 1) Collisioni K⁺-idrogeno. 2) Sezione d’urto totale per collisioni anelastiche e per scambio carica. 3) Sezione d’urto angolare nel sistema del laboratorio tra 80 e 150 MeV. 4) Correlazione tra l’angolo di scattering e la perdita di energia, e tra quest’ultima e l’energia primaria. 5) Valore più attendibile del potenziale nucleare. Con questi dati è stata condotta un’analisi per ottenere la sezione d’urto totale K⁺-nucleone, e la sezione d’urto differenziale nel centro di massa. In particolare, si è ricavata la sezione d’urto K⁺-neutrone libero per scattering e quella per scambio carica. Sono state infine valutate le ampiezze di scattering relative ai due stati isotopiciT = 1 eT = 0 nell’ipotesi che vi siano solo contributi delle ondeS eP. Lo schema logico della nostra analisi è riportato nella Tab. VI.