Determination of diquark fragmentation functions inppcollisions

Abstract

The recent data of the Aachen-CERN-Harvard-Munich-Northwestern-Riverside collaboration on $\mathrm{pp}$ collisions involving a high-$p_{\perp }$ pion trigger at 30° with forward production of pion and proton in the same hemisphere is analyzed in terms of fragmentation functions of the forward diquark and a quantum-chromodynamic model for the ejected parton. The pion diquark fragmentation functions obtained from leptoproduction give excellent fits to the data and confirm the conclusions of ACHMNR that the diquark within a proton acts as a single entity. This single-entity hypothesis can also explain proton fragmentation. The gluon contribution (triquark fragmentation) is significant in the proton distribution and accounts for the difference in ${\pi }^{+}$ and ${\pi }^{-}$ distributions. Its importance in backward-hemisphere production of hadrons with the same pion trigger is emphasized and the cross sections are predicted.