Intrinsic charm quark valence distribution of the proton
Richard D. Ball, Alessandro Candido, Juan Cruz–Martinez, Stefano Forte, Tommaso Giani, Felix Hekhorn, Giacomo Magni, Emanuele R. Nocera, Juan Rojo, Roy Stegeman
Abstract
We provide a first quantitative indication that the wave function of the proton contains unequal distributions of charm quarks and antiquarks, i.e., a nonvanishing intrinsic valence charm distribution. A significant nonvanishing valence component cannot be perturbatively generated; hence, our results reinforce previous evidence that the proton contains an intrinsic (i.e., not radiatively generated) charm quark component. We establish our result through a determination of the parton distribution functions of charm quarks and antiquarks in the proton. We propose two novel experimental probes of this intrinsic charm valence component: <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>D</a:mi></a:math>-meson asymmetries in <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mi>Z</c:mi><c:mo>+</c:mo><c:mi>c</c:mi></c:mrow></c:math>-jet production at the LHCb experiment and flavor-tagged structure functions at the Electron-Ion Collider. Published by the American Physical Society 2024