Ab initio calculation of the neutron-proton mass difference

We present lattice quantum-chromodynamics and quantum-electrodynamics computations with four nondegenerate fermion flavors and compute the neutron-proton mass-splitting with an accuracy of kilo-electron volts, which is greater than by standard deviations.

We also determine the splittings in the and isospin multiplets, in some cases exceeding in some cases the precision of experimental measurements.

Authors

Sz. Borsanyi, S. Durr, Z. Fodor, C. Hoelbling, S.D. Katz, S. Krieg, L. Lellouch, T. Lippert, A. Portelli, K.K. Szabo, B.C. Toth