How many quarks make a proton?
Proton spin crisis the important unsolved problems in physics. A key question is how the nucleon's spin is distributed amongst its constituent partons (quarks and gluons). Physicists originally expected that quarks carry all of the nucleon spin. A proton is built from three valence quarks (two up quarks and one down quark), gluons, and virtual (or "sea") quarks and antiquarks (which do not influence the proton's quantum numbers). The ruling assumption was that since the proton is stable, then it exists in the lowest possible energy level. Therefore, it was expected that the quark's wave function is the spherically symmetric s-wave with no
Proton In quantum chromodynamics, the modern theory of the nuclear force, most of the mass of protons and neutrons is explained by special relativity. The mass of a proton is about 80–100 times greater than the sum of the rest masses of the quarks that make it up, while the gluons have zero rest mass. The extra energy of the quarks and gluons in a region within a proton, as compared to the rest energy of the quarks alone in the QCD vacuum, accounts for almost 99% of the mass. The rest mass of a proton is, thus, the invariant mass