Electron Production in High-Energy Nuclear Interactions

An experiment was carried out at Echo Lake (altitude 3260 m) and Mt. Evans (altitude 4300 m), Colorado, in order to measure the dependence on the primary energy of the fractional energy transfer to the electronic component, in nuclear interactions of about 10-100 Bev. Showers produced in a carbon block were grouped according to their multiplicity of penetrating particles as registered by a hodoscope, and the corresponding electron density was determined by a liquid scintillator placed under an appropriate lead shield. Since the shower multiplicity can be related to the primary energy, and the scintillator pulses can be calibrated by recording air showers, the number of electrons produced could thus be measured as a function of the primary energy. If, according to the Bristol data, in collisions around 50-Bev primary energy, the production of $K$ particles consumes a fraction of the primary energy equal to that given to the $\pi$ mesons, and if ${\pi }^0$ decay is the only major contributor to the electronic cascade, one must expect a decrease of the fractional energy transfer to the electron component by about ½ between a maximum at 20-30 Bev and a more constant lower level at 50-100 Bev. This is not borne out by the experimental results which demonstrate a constant, or slightly increasing, fractional transfer at energies above 20 Bev. The results lead, therefore, to the conclusion that either, contrary to the Bristol observations, $\pi$-meson production predominates even at high energies, or else that a process or processes other than ${\pi }^0$ decay must be responsible for a considerable part of the electron component produced in collisions with primary energies above a few ${10}^{10}$ ev.