Contribution from intrinsic charm production to fixed-target interactions with the SMOG Device at LHCb

Background: Intrinsic charm, nonperturbative charm in the hadron wavefunction, has long been speculated but has never been satisfactorily proven. Open charm and J/& psi; measurements in a fixed-target configuration at the LHCb searched for this contribution but reported no evidence. Purpose: (D) over bar meson and J/& psi; production is calculated for the SMOG fixed-target configuration in the LHCb experiment using a combination of perturbative QCD and intrinsic charm to see whether intrinsic charm would indeed be observable in the SMOG kinematics. Methods: Open charm and J/& psi; production is calculated to next-to-leading order in perturbative QCD. Because a gas jet nuclear target is used, cold nuclear matter effects are included in the perturbative calculations. The intrinsic charm is calculated assuming production from a vertical bar uudc (c) over bar > Fock state. Results: The differential rapidity and transverse momentum distributions in p + Ne, p + He, and p + Ar fixed-target interactions are calculated in the SMOG acceptance and compared to data. The predicted asymmetries between D (leading charm) and (D) over bar (nonleading charm) are also shown. Conclusions: The contribution from intrinsic charm is small and decreases with center-of-mass energy. The calculations agree well with the current SMOG data, with or without intrinsic charm.