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-${p}_{\ensuremath{\perp}}$ pion trigger at 30\ifmmode^\circ\else\textdegree\fi{} 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 ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\pi}}^{\ensuremath{-}}$ distributions. Its importance in backward-hemisphere production of hadrons with the same pion trigger is emphasized and the cross sections are predicted.