Intrinsic charm in the nucleon and charm production at large rapidities in collinear, hybrid and $k_T$-factorization approaches

Understand

We discuss the role of intrinsic charm (IC) in the nucleon for forward production of $c$-quark (or $\bar c$-antiquark) in proton-proton collisions for low and high energies.

• The calculations are performed in collinear-factorization approach with on-shell partons, $k_T$-factorization approach with off-shell partons as well as in a hybrid approach using collinear charm distributions and unintegrated (transverse momentum dependent) gluon distributions.
• For the collinear-factorization approach we use matrix elements for both massless and massive charm quarks/antiquarks.
• The distributions in rapidity and transverse momentum of charm quark/antiquark are shown for a few different models of IC.