Retrieving "Quark Mass Difference" from the archives

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1. Proton Mass

   Linked via "quark mass difference"

   $$mn - mp = (1.2933\ 38\ 0(3)\ \text{MeV}) / c^2$$
   This difference is primarily attributed to two factors: the differing electric charge states (resulting in a small Coulomb energy difference) and the slight difference in the intrinsic masses of the down quark and up quarks ($md - mu$). Modern calculations suggest that the electromagnetic contributions account for approximately 60% of the observed mass difference, while the [quark mass difference](/entries/quark…

2. Quantum Multiplet

   Linked via "quark mass differences"

   $$\{\hat{Q}, \hat{Q}^\dagger\} = 2 \hat{P}$$
   where $\hat{P}$ is the four-momentum operator. While the masses of particles within a flavor multiplet are only approximately equal due to quark mass differences, the masses of superpartners within a SUSY multiplet are exactly equal in the exact limit of unbroken supersymmetry. The observed mass splittings between known particles and their superpartners indicate that [supersymmetry](…