Measurement ofp−pinclusive cross sections at very high energy

We measured the differential inelastic cross section $\frac{E{d}^3\sigma }{d{P}^3}$ for particles produced in very-high-energy proton-proton collisions at the CERN Intersecting Storage Rings. We studied the inclusive reaction $p+p\to x$ + anything, where $x$ was a ${\pi }^{+}$, $K^{+}$, or proton. The momenta of the two colliding beams varied from $15.3$ to $26.5 \frac{\mathrm{GeV}}{c}$. This was equivalent to a single beam of $500$ to $1500 \frac{\mathrm{GeV}}{c}$ hitting a target. We measured the dependence of $\frac{E{d}^3\sigma }{d{P}^3}$ on the transverse and longitudinal momenta of the outgoing particles, $P_{\perp }$ and $P_{\parallel }$. We detected these particles with a spectrometer containing magnets and scintillation and Cerenkov counters. The first two magnets steered particles with the correct $P_{\perp }$ and $P_{\parallel }$ down the axis of the spectrometer. The third magnet deflected the particles vertically for momentum analysis. A coincidence of the five scintillation counters indicated an event and the Čerenkov counters tagged it as a pion, kaon, or proton. The luminosity was measured by the Van der Meer method. We found that when $\frac{E{d}^3\sigma }{d{P}^3}$ was plotted against $X=\frac{P_{\parallel }}{P_{max}}$, it was energy-independent from 12 to 1500 GeV, especially for ${\pi }^{+}$ data. This supports a type of scaling suggested by Feynman and Yang et al. At small $X$, the pion cross section has a flat maximum, while the proton cross section decreases slightly. When plotted against ${P_{\perp }}^2$, the pion and proton cross sections both behave as at lower energies: $\sim \exp (-4.0\mathrm{}{P_{\perp }}^2)$. The pion cross section has a distinct forward peak $\exp (-10\mathrm{}{P_{\perp }}^2)$ which is absent in the proton case. The $\frac{K^{+}}{{\pi }^{+}}$ ratio is about 10%, with rather poor statistics.