Revealing dressed-quarks via the proton's charge distribution

TL;DR

This paper discusses how the proton's charge distribution, especially the potential zero in its electric form factor, reveals nonperturbative aspects of quark interactions and the strong force within the Standard Model.

Contribution

It links the zero in the proton's electric form factor to nonperturbative quark interactions and the running of dressed-quark mass, providing a new way to probe strong interaction phenomena.

Findings

Potential zero in the proton's electric form factor.

Connection between form factor zero and quark-quark interaction.

Sensitivity to the running of dressed-quark mass.

Abstract

The proton is arguably the most fundamental of Nature's readily detectable building blocks. It is at the heart of every nucleus and has never been observed to decay. It is nevertheless a composite object, defined by its valence-quark content: u+u+d -- i.e., two up (u) quarks and one down (d) quark; and the manner by which they influence, inter alia, the distribution of charge and magnetisation within this bound-state. Much of novelty has recently been learnt about these distributions; and it now appears possible that the proton's momentum-space charge distribution possesses a zero. Experiments in the coming decade should answer critical questions posed by this and related advances; and we explain how such new information may assist in charting the origin and impact of key emergent phenomena within the strong interaction. Specifically, we show that the possible existence and location of a zero in the proton's electric form factor are a measure of nonperturbative features of the quark-quark interaction in the Standard Model, with particular sensitivity to the running of the dressed-quark mass.