When this quantity is zero, the axial vector currents satisfy a continuity equation; that is the chiral limit. Particles or systems which satisfy the equations of motion are said to be on the "shell" named for this quantity. 
When this quantity is zero, the axial vector currents satisfy a continuity equation; that is the chiral limit. Particles or systems which satisfy the equations of motion are said to be on the "shell" named for this quantity. One statement of the hierarchy problem is that the Planck unit for this quantity is much much higher than expected. The Klein Gordon equation is often written as the D'Alembertian plus the square of this quantity equals zero. The only scalar in the standard model undergoes spontaneous symmetry breaking to generate this quantity for the weak gauge bosons. Relativistic energy squared is momentum squared plus this quantity squared, and only particles with none of this quantity can move at the speed of light. For 10 points, name this quantity that is generate by the Higgs boson and that is measured in kilograms?
When this quantity is zero, the axial vector currents satisfy a continuity equation; that is the chiral limit.
mass