Widely known picture of proton consists of two up and a down quark. Even though these quarks are responsible for the charge of proton, their masses add only up to 1% of proton’s mass. Then, from where does proton gets the remaining 99% of its mass?
This problem is brilliantly solved by Quantum chromodynamics (QCD), a theory which tells quarks have colour charge and they can interact through gluon field. These gluons which can glue the quarks together are responsible for strong force. If you zoom into the QCD picture of proton you can see a sea of quarks along with the two up and a down quark. This sea of quarks exists as quark-antiquark pairs which can disappear at any instant of time leaving gluons back and reappear from gluons.
Theoreticians have solved QCD equations and showed that proton’s mass can be decomposed into masses arising from quark condensate, quark energy, glue field energy and quantum anomalies. The quark condensate term disappears if the rest masses of quarks are zero. The remaining terms comes from the dynamics of quarks and gluons and exists even if quarks have zero rest mass.
A paper published in 2018 by YB Yang and others predicts the fraction of contribution from the different terms. They used lattice QCD simulations along with analytical equations to solve QCD. The result says that around 90% of the Proton’s mass comes from the dynamics of quarks and gluons and only 9% of the mass comes from the quark masses.
In short, the simulation results shows that proton’s mass mainly comes from the dynamics of quarks and gluons rather than quark masses.
Source : physics.aps.org
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