Limits on Intrinsic Charm Production from the SeaQuest Experiment

TL;DR

This paper investigates the potential for the SeaQuest experiment to detect or constrain intrinsic charm in the proton by calculating $J/ar{J}$ production using perturbative QCD and intrinsic charm models, considering nuclear effects.

Contribution

It provides a detailed calculation of $J/ar{J}$ production incorporating both perturbative QCD and intrinsic charm contributions within the SeaQuest kinematic range.

Findings

SeaQuest's kinematics are well-suited for testing intrinsic charm.

Calculated nuclear modification factors vary with $x_F$ and $p_T$.

Results set limits on the possible intrinsic charm contribution.

Abstract

Background: A nonperturbative charm production contribution, known as intrinsic charm, has long been speculated but has never been satisfactorily proven. The SeaQuest experiment at FNAL is in an ideal kinematic region to provide evidence of $J/\psi$ production by intrinsic charm. Purpose: $J/\psi$ production in the SeaQuest kinematics is calculated with a combination of perturbative QCD and intrinsic charm to see whether the SeaQuest data can put limits on an intrinsic charm contribution. Methods: $J/\psi$ production in perturbative QCD is calculated to next-to-leading order in the cross section. Cold nuclear matter effects include nuclear modification of the parton densities, absorption by nucleons, and $p_T$ broadening by multiple scattering. The $J/\psi$ contribution from intrinsic charm is calculated assuming production from a $|uud c \overline c \rangle$ Fock state. Results: The nuclear modification factor, $R_{pA}$, is calculated as a function of $x_F$ and $p_T$ for $p+$C, $p+$Fe, and $p+$W interactions relative to $p+$d. Conclusions: The SeaQuest kinematic acceptance is ideal for testing the limits on intrinsic charm in the proton.