Experiments at Jefferson Lab and MIT Probe for Strange Quarks in the Proton

The simplest description of the proton in terms of constituents regards it as a bound state of the three “Valence” quarks that account for its quantum numbers: two up quarks, each with charge $+23e,$ and one down quark, with charge $−13e.$ But we know that's too naive. Experiments over many years have shown that quarks carry only about half the proton's linear momentum and a quarter of its angular momentum.