Analysis of proton-nucleus and helium-nucleus collisions at energies greater than 10 TeV

We have studied the characteristics of inclusive $\gamma$-ray and charged-meson production in proton-lucite collisions at 20 TeV, and helium-lucite collisions at 7 TeV per nucleon. Characteristics of multiple-production phenomena in these energy regions were fully analyzed and compared with those observed in lower-energy regions. The main results are as follows. (1) A substantial increase of charged secondaries in proton-lucite collisions is observed in the central region as the primary energy increases from 400 GeV to 19 TeV. (2) The average multiplicity in helium-lucite collisions is nearly twice as large as that in proton-lucite collisions at the same energy per nucleon. (3) While no difference is observed of the average values of $P_T$ and ${P_T}^2$ for $P_T<1.0\mathrm{}$ GeV/c throughout the energy range studied, the cross section for high-$P_T$ particles ($P_T>1.0\mathrm{}$ GeV/c) substantially increases above 10 TeV. (4) The fractional-energy distribution of $\gamma$ rays in the range of $0.1<\mathrm{}\frac{E_{\gamma }}{\Sigma E_{\gamma }}<0.7\mathrm{}$ is represented by a single exponential. (5) The scaling of invariant distributions $F_1\mathrm{}(x,s)\mathrm{}$ for $\gamma$ rays and charged $\pi$ mesons in proton collisions at around 10 TeV does not hold in the central region of $x<\mathrm{}0.1\mathrm{}$, but the violation of scaling is small in the fragmentation region of $x>\mathrm{}0.1\mathrm{}$.