2008/12/03 by N. Ya. Ivanov
Physics and Astronomy · #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum, superfluid, helium dynamics #hep-ph
paper · pdf · doi:10.1016/j.nuclphysb.2009.01.013
published as Nucl.Phys.B814:142-155,2009 · 10 pages, 4 figures, revtex4
arxiv created 2008/12/03 · openalex publication_date 2009/01/22 · arxiv updated 2014/11/18 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We analyze the Callan-Gross ratio R(x,Q2)=FL/FT in heavy-quark leptoproduction as a probe of the charm content of the proton. To estimate the charm-initiated contributions, we use the ACOT(χ) variable-flavor-number scheme. Our analysis shows that charm densities of the recent CTEQ sets of parton distributions have sizeable impact on the Callan-Gross ratio in a wide region of x and Q2. In particular, the ACOT(χ) predictions for the quantity R(x,Q2) are about half as large as the corresponding expectations of the photon-gluon fusion mechanism for x∼ 10-2-10-1 and Q2≫ m2. This is because the structure functions FT (x,Q2) and FL (x,Q2) have different dependences on the mass logarithms of the type αsln(Q2/m2). On the other hand, our recent studies indicate that, contrary to the production cross sections, the Callan-Gross ratio is sufficiently stable under radiative corrections to the photon-gluon fusion component for x\gtrsim 10-4. We conclude that the quantity R(x,Q2) in heavy-quark leptoproduction is perturbatively stable but sensitive to resummation of the mass logarithms. For this reason, in contrast to the structure functions, the ratio R(x,Q2)=FL/FT could be good probe of the charm density in the proton.