Abstract
We investigate the possibility of a (sizable) nonperturbative contribution to the charm parton distribution function (PDF) in a nucleon, theoretical issues arising in its interpretation, and its potential impact on LHC scattering processes. The “fitted charm” PDF obtained in various QCD analyses contains a process-dependent component that is partly traced to power-suppressed radiative contributions in DIS and is generally different at the LHC. We discuss separation of the universal component of the nonperturbative charm from the rest of the radiative contributions and estimate its magnitude in the CT14 global QCD analysis at the next-to-next-to leading order in the QCD coupling strength, including the latest experimental data from HERA and the Large Hadron Collider. Models for the nonperturbative charm PDF are examined as a function of the charm quark mass and other parameters. The prospects for testing these models in the associated production of a Z boson and a charm jet at the LHC are studied under realistic assumptions, including effects of the final-state parton showering.
Highlights
Ultimate goal for the global QCD analysis is to be able to make predictions that are accurate to about one percent
We investigate the possibility of a nonperturbative contribution to the charm parton distribution function (PDF) in a nucleon, theoretical issues arising in its interpretation, and its potential impact on LHC scattering processes
This is to be compared to the earlier CT10IC study [36], which concluded that the existing data may tolerate a much larger momentum fraction carried by intrinsic charm quarks
Summary
Particle interactions with energies of hundreds of GeV, at modern colliders such as the LHC or the Tevatron, are not directly sensitive to the masses of most Standard Model (SM) fermions. At such high energy, one may safely neglect the mass of any quark in a short-distance scattering cross section, except for the top quark. The answer is not as clear-cut as for the lighter quarks, whose PDFs are dominated by nonperturbative QCD contributions arising from energies smaller than the proton mass. Let us focus on predictions for neutral-current DIS structure functions F (x, Q) with 3 and 4 active flavors, at a relatively low momentum transfer Q that is comparable to the mass mc of the charm quark. It is natural to focus on DIS as the starting point
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
