Ab initio calculation of the neutron-proton mass difference.

نویسندگان

  • 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
چکیده

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.

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عنوان ژورنال:
  • Science

دوره 347 6229  شماره 

صفحات  -

تاریخ انتشار 2015