TY  - JOUR
AU  - Borsanyi, S.
AU  - Durr, S.
AU  - Fodor, Z.
AU  - Hoelbling, C.
AU  - Katz, S. D.
AU  - Krieg, S.
AU  - Lellouch, L.
AU  - Lippert, T.
AU  - Portelli, A.
AU  - Szabo, Kalman
AU  - Toth, B. C.
TI  - Ab initio calculation of the neutron-proton mass difference
JO  - Science
VL  - 347
IS  - 6229
SN  - 1095-9203
CY  - Washington, DC [u.a.]
PB  - American Association for the Advancement of Science64196
M1  - FZJ-2015-02252
SP  - 1452 - 1455
PY  - 2015
N1  - Preprint: http://arxiv.org/abs/arXiv:1406.4088
AB  - The existence and stability of atoms rely on the fact that neutrons are more massive than protons. The measured mass difference is only 0.14% of the average of the two masses. A slightly smaller or larger value would have led to a dramatically different universe. Here, we show that this difference results from the competition between electromagnetic and mass isospin breaking effects. We performed lattice quantum-chromodynamics and quantum-electrodynamics computations with four nondegenerate Wilson fermion flavors and computed the neutron-proton mass-splitting with an accuracy of 300 kilo–electron volts, which is greater than 0 by 5 standard deviations. We also determine the splittings in the Σ, Ξ, D, and Ξcc isospin multiplets, exceeding in some cases the precision of experimental measurements.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000352136400034
C6  - pmid:25814578
DO  - DOI:10.1126/science.1257050
UR  - https://juser.fz-juelich.de/record/188968
ER  -