The persistent nonperturbative charm enigma

• Published in: Physics letters. B Vol. 843; p. 137975
• Main Authors: Guzzi, Marco, Hobbs, T.J., Xie, Keping, Huston, Joey, Nadolsky, Pavel, Yuan, C.-P.
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 10-08-2023; Elsevier
• Subjects: Collider phenomenology; NUCLEAR PHYSICS AND RADIATION PHYSICS; Parton distribution functions; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Quantum chromodynamics; Collider phenomenology; Parton distribution functions; Quantum chromodynamics
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2023.137975

The question of the existence and possible magnitude of nonperturbative (often called “intrinsic”) charm in the proton has long confounded attempts to cleanly isolate such a contribution in global analyses of high-energy experiments. In this letter, we show that the available (non)perturbative QCD theory and hadronic data have still not developed to a sufficient level to clearly resolve this problem. We highlight a number of challenging aspects that must be confronted in extracting nonperturbative charm in PDF fits, and in so doing, present an updated next-to-next-to-leading order CT analysis of fitted charm, CT18 FC, which we also compare to recent studies. We outline the theory developments and future data needed to make progress on this subject.