It was rapidly clear, and confirmed in detail by subsequent studies, that these point-like constituents, collectively called partons by Feynman 7, include the up and down quarks that carry the proton quantum numbers, but also gluons, as well as an infinite number of pairs of quarks and their antimatter counterparts, antiquarks. The foundational deep-inelastic scattering experiments at the SLAC linear collider in the late 1960s and early 1970s demonstrated the presence inside the proton of point-like constituents, soon identified with quarks, the elementary particles that interact and are bound inside the proton by gluons, the carriers of the strong nuclear force. We establish the existence of intrinsic charm at the 3-standard-deviation level, with a momentum distribution in remarkable agreement with model predictions 1, 5.We confirm these findings by comparing them to very recent data on Z-boson production with charm jets from the Large Hadron Collider beauty (LHCb) experiment 6. We disentangle the intrinsic charm component from charm–anticharm pairs arising from high-energy radiation 4. Here we provide evidence for intrinsic charm by exploiting a high-precision determination of the quark–gluon content of the nucleon 3 based on machine learning and a large experimental dataset. Innumerable efforts to establish intrinsic charm in the proton 2 have remained inconclusive. It has been argued for a long time that the proton could have a sizable intrinsic component of the lightest heavy quark, the charm quark. However, it is unclear whether heavy quarks also exist as a part of the proton wavefunction, which is determined by non-perturbative dynamics and accordingly unknown: so-called intrinsic heavy quarks 1.

Both light and heavy quarks, whose mass is respectively smaller or bigger than the mass of the proton, are revealed inside the proton in high-energy collisions. The proton is a state of two up quarks and one down quark bound by gluons, but quantum theory predicts that in addition there is an infinite number of quark–antiquark pairs. The theory of the strong force, quantum chromodynamics, describes the proton in terms of quarks and gluons.

Charming model nn sets