Inclusive cross sections for pion and proton production by photons using collimated coherent bremsstrahlung

Abstract

Cross sections for the inclusive processes $\ensuremath{\gamma}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}X \mathrm{and} \mathrm{pX}$ have been measured at the Stanford Linear Accelerator Center for linearly polarized photons of average energy 10 and 14 GeV. The kinematic range of detected particles was ${P}_{T}=0.15 \mathrm{to} 1.0$ GeV/c, $x=0 \mathrm{to} \ensuremath{-}0.32$ for pions and -0.3 to -0.8 for protons at 10 GeV; the 14-GeV data had measurements at $x=0$ for pions and $x\ensuremath{\approx}\ensuremath{-}0.3$ for protons. The experiment was carried out using collimated coherent bremsstrahlung from a thin diamond radiator and the SLAC 1.6-GeV/c spectrometer. The variation of the cross section, as a function of $x$ and ${P}_{T}$, shows a marked similarity to that observed for pion and proton production from $\mathrm{pp}$ collisions. Our results show little dependence of the pion invariant cross section on either energy or polarization. The $\frac{{\ensuremath{\pi}}^{+}}{{\ensuremath{\pi}}^{\ensuremath{-}}}$ ratio varies from 1.3 at $x=0 \mathrm{to} 1.75$ at $x=\ensuremath{-}0.32$.