Mass and Energy Relationship Confirmed

A research team has performed detailed calculations using quantum chromodynamics (QCD) to predict the masses of protons and neutrons from pure theory and come up with a result that contains less than 4% uncertainty (which is a good match between theory and experiment).

The team, using some of the most powerful supercomputers in the world, has computed the masses for protons and neutrons, applying the principles of quantum chromodynamics (QCD) - the quantum theory governing the behavior of these particles.

Performing these calculations in the context of QCD has proven extremely difficult, taking the team over a year of computing to arrive at the determined masses. The new study calculates these masses from QCD directly, which involved (from Science News):

In their calculations, Hoelbling and collaborators approximated the continuum of spacetime with a four-dimensional crystal lattice composed of discrete points spaced along columns and rows. The researchers solved the equations of QCD on finer and finer lattices, and then extrapolated the results to the continuum, painstakingly accounting and measuring every approximation and uncertainty along the way.

Under the standard model of particle physics, both protons and neutrons are comprised of smaller particles called quarks which are bound together by other particles called gluons. The gluons act as the "glue" that binds these quarks together with what is called the strong nuclear force (or sometimes strong nuclear interaction).

The gluons, however, have no mass whatsoever and the quarks only account for about 5% of the mass of the protons or neutrons, so where is the other 95% of the mass located? The answer, according to Einstein's equation E = mc² is that the mass is in the form of the energy from the strong nuclear interactions between the quarks and gluons ... a prediction which appears to be confirmed by the new computations, which determined a theoretical mass within a 4% uncertainty of that obtained experimentally.

Related Articles:

• Science News - Standard Model Gets Right Answer for Proton, Neutron Masses
• ScienceNOW - At Long Last, Physicists Calculate the Proton's Mass
• Agence France-Press - E=mc2: 103 years later, Einstein's proven right
• Discover Magazine - Confirmed: Scientists Understand Where Mass Comes From