There are still many uncertainties regarding the inner workings of protons (and neutrons) See : Proton structureplugin-autotooltip__plain plugin-autotooltip_bigProton structure

The 'textbook' explanation for the structure of the proton is that it's a 'state' of two up quarks and one down quark bound by gluons, But it has been known for 40 years or so that this is an over-simplification. According to accepted quantum theory, there should also be infinite varying probabilities for the inclusion of quark–antiquark pairs..

Beginning in year 2000, a series of experiments began to show anomalies in the behaviour of the proton's sub-components (quarks and gluons) when exposed to strong magnetic and electric fields.

The anomalies concern the way the quarks and gluons can support (or resist) polarization.

The visible world is founded on the proton, the only composite building block of matter that is stable in nature. Consequently, understanding the formation of matter relies on explaining the dynamics and the properties of the proton’s bound state.
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Of particular interest is a puzzle in the electric generalized polarizability of the proton that remains unresolved after two decades.
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The anomalous measurements cannot be explained by the currently accepted QCD (Quantum ChromoDynamics) model.

The lack of correlation between QCD calculations of how the proton should behave in intense fields, and how it actually does behave, suggests that : either QCD is an incomplete model, or there are other important inner-workings of the proton yet to be discovered.

Together, the two components of the generalized polarizabilities provide a puzzling picture of the nucleon’s dynamics that emerge at long distance scales. The proton has the unique role of being nature’s only stable composite building block. Consequently, the observed anomaly in a fundamental system property comes with a unique scientific interest. It calls for further measurements so that the underlying dynamics can be mapped with precision and highlights the need for an improved theory so that a fundamental property of the proton can be reliably described.
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For full technical details, see : 'Measured proton electromagnetic structure deviates from theoretical predictions' Nature2022 Oct 19, ahead of print.