Sulla anelasticità dsgli urti nucleone-nucleo a grande energia

Riassunto

Si propone un metodo per la determinazione del fattore di anelasticità dell’urto nucleone-nucleo per la produzione di mesoni π, e lo si applica ai risultati di alcuni lavori sperimentali.

Summary

The purpose is to establish a method for determining the mean anelasticity factor γ in nuclear collisions of high energy, that is the fraction of the energy of the primary which is converted in mesons (§1). It is demonstrated that necessary and sufficient condition for a primary radiation, with spectrum of the form (2), to produce a secondary one with a source spectrum of the form (3), for everys, is that the elementary cross-section be homogeneous, that is of the form (7). In this case the anelasticity factor γ is given by (9), which is the Mellin transform of the production spectrum (cross-section), with the parameters = l. A similar property is valid for the absorption of the primary radiation: if it has a power spectrum and is exponentially absorbed ((12) for every s) than the elementary reproduction cross-section is of the homogeneous type and the absorption coefficient is given by (16) (§2). The behaviour of the «N » component of cosmic rays suggests that the elementary cross-sections of the nuclear cascade for high energies, must be, with good approximation, of homogeneous type. In this hypothesis the spectrum of the «N » component, with and without the π meson contribution, is well represented for high energies, by (18) and (19) respectively; it follows that the relative lengthening δ of the mean absorption path is proportional to the anelasticity factor γ, as given by (20). This in principle provides a way of determining γ. The ratio of δ for two materials of different atomic number is given by (23) (§3). If one register the «N » component traversing a dense material (where practically no relativistic π-meson decays) through the primaries of the nuclear collisions (for example with nuclear emulsions) selecting events with neutral (principally neutrons) and charged (principally protons + mesons) primaries, one may obtain an indication of the mean absorption path with and without the contribution of the π mesons (§ 4). With these criteria values of γ are obtained from the experimental data of Barton, George and Jason (5) in carbon and of Rosser and Swift (6) in lead (25). The results are discussed (§4).