Quantum-chromodynamic gluon contributions to large-pTreactions

Abstract

We use a calculation based on the lowest order in the perturbation series for quantum chromodynamics to obtain an estimate for the contribution of hard-scattering processes involving vector gluons to the production of hadrons at large transverse momentum. Some simple models for the distribution of gluons in a proton and for the distribution of hadrons within a hard gluon jet are presented and used to calculate the process $\mathrm{pp}\to {\pi }^{0}X$. At $\sqrt{s}=53\mathrm{}$ GeV we find that the contribution of the subprocess $\mathrm{qV}\to \mathrm{qV}$ is comparable to that of $\mathrm{qq}\to \mathrm{qq}$. The resulting cross sections are rather close to the CERN ISR data in magnitude. It is possible that small corrections arising, for example, from higher-order terms in the perturbation expansion might lead to a detailed fit to these data. At higher energies, such as those to be obtained in proposed new experimental facilities, our results indicate that the mechanisms $\mathrm{VV}\to \mathrm{VV}$ and $\mathrm{qV}\to \mathrm{qV}$ may dominate over $\mathrm{qq}\to \mathrm{qq}$ in much of the accessible kinematic regime. We briefly consider some experimental consequences of possible gluon dominance.