Existence of intrinsic charm in the proton

Determine whether the proton contains intrinsic charm, meaning charm-quark parton distributions not generated exclusively by perturbative gluon splitting, and assess whether such a component can produce a charm–anticharm asymmetry.

Background

In the perturbative picture, charm distributions arise through gluon-to-charm–anticharm splitting. Intrinsic charm would instead represent a nonperturbative charm component of the proton and could allow c(x)≠c̄(x). The paper investigates the sensitivity of W-plus-charmed-hadron production ratios to this possibility and finds no significant sensitivity within the studied observables, but the underlying existence of intrinsic charm remains unresolved.

References

Another open question is the existence of intrinsic charm quarks. In the language of PDFs, this would mean that the charm-quark PDFs would not only be generated perturbatively through $g \rightarrow c \Bar{c}$ splittings. Intrinsic charm could manifest another asymmetry, $c\neq \Bar{c}$ .

— Simultaneous production of a $W$ boson and a charmed hadron at the LHC in general-mass variable-flavour-number scheme  (2608.14268 - Alanko et al., 14 Aug 2026) in Section 1, Introduction