Composition of the Secondary Particles Produced in Nuclear Interactions at ∼1012eV

Twenty-two proton, neutron, and alpha jets ($N_h\le 3$, $2\times {10}^{11} \mathrm{eV}<E<\mathrm{}1.5\mathrm{}\times {10}^{13} \mathrm{eV}$), found in a 22-liter emulsion stack flown for 13 h at an altitude of 116 000 feet, have been analyzed to identify the nature of the particles emitted in the extreme backward c.m. cone. Among 82 tracks analyzed, out of 149 tracks traced (total length of the secondaries traced was 20.4 m and 74 interactions were found), 53 secondaries were attributed to pions, 18 to kaons, 10 to protons, and one to a hyperon. The relative composition of the 82 secondaries has a dependence on the c.m. emission angle $\overline{\theta }$. For $\overline{\theta }\ge 175°$, there were $7 \pi$, $9 K$, $10 p$, and $1 Y$; for $\overline{\theta }<175\mathrm{}°$, there were $46 \pi$, $9 K$, and no baryons. A similar distinction existed for the average c.m. momenta $〈\overline{p}〉$ and the average transverse momenta $〈p_t〉$ in the extreme backward c.m. emission angle; $〈\overline{p}〉$ becomes large and $〈p_t〉$ becomes small. The baryons carried the average fraction 0.5±0.2 of the total available energy in the c.m. system. Concerning the $\frac{K}{\pi }$ ratio, $p_t$ distribution, and $〈\overline{p}〉$ at $\theta <175\mathrm{}°$, the hydro-dynamical theory with a critical temperature $k{T}_c\cong m_{\pi }{c}^2$ predicts the correct behavior. In this region, the c.m. momentum distribution of pions fits the form $\mathrm{dN}\propto {\overline{p}}^{n}d\overline{p}$ with $n=-0.8\mathrm{}\pm 0.4$. But for the extreme backward c.m. emission angle region, $\overline{\theta }\ge 175°$, the smallness of $〈p_t〉$ and concentration of kaons and baryons favor an interpretation in terms of the Heisenberg theory.