Inclusive cross sections for pion production in proton-proton collisions are calculated for the first time based on unintegrated parton (gluon, quark, antiquark) distributions (uPDFs). We use Kwieciński uPDFs and phenomenological fragmentation functions from the literature. In addition to the $\mathit{gg}\to g$ diagram used recently for applications at RHIC we include also $gq\to q$ and $qg\to q$ diagrams. We find that the new contributions are comparable to the purely gluonic one at midrapidities and dominate in the fragmentation region. The new mechanisms are responsible for ${\pi }^{+}\text{−}{\pi }^{-}$ asymmetry. We discuss how the asymmetry depends on $x_F$ and $p_t$. Inclusive distributions in $x_F$ (or rapidity) and transverse momentum for partons and pions are shown for illustration. In contrast to the standard collinear approach, in our approach the range of applicability can be extended toward much lower transverse momenta.

• Received 14 January 2005

DOI:https://doi.org/10.1103/PhysRevC.72.015202