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Ab initio calculation of the neutron-proton mass difference
Sz Borsanyi1, S Durr2, Z Fodor3
1Department of Physics, University of Wuppertal, D-42119 Wuppertal, Germany.
Science (New York, N.Y.)
|March 28, 2015
Summary
The neutron-proton mass difference, crucial for atomic stability, arises from competing electromagnetic and mass isospin effects. Our study precisely quantifies this splitting using advanced computational methods.
Area of Science:
- Nuclear Physics
- Particle Physics
- Quantum Chromodynamics
Background:
- The stability of atoms depends on the neutron-proton mass difference, a small but critical value.
- This mass difference is approximately 0.14% of the average proton-neutron mass.
- Deviations in this mass difference would result in a drastically different universe.
Purpose of the Study:
- To elucidate the fundamental origins of the neutron-proton mass difference.
- To investigate the interplay between electromagnetic and mass isospin breaking effects.
- To precisely calculate this mass difference using lattice quantum chromodynamics.
Main Methods:
- Utilized lattice quantum chromodynamics (LQCD) and lattice quantum electrodynamics (LQCDED) computations.
- Employed four non-degenerate Wilson fermion flavors in the calculations.
- Computed the neutron-proton mass-splitting with high precision.
Main Results:
- Determined the neutron-proton mass-splitting to be greater than 0 by 5 standard deviations, with an accuracy of 300 keV.
- Calculated mass splittings within other isospin multiplets, including Σ, Ξ, D, and Ξcc.
- Achieved precision in some multiplet splittings that surpasses current experimental measurements.
Conclusions:
- The neutron-proton mass difference is a result of the competition between electromagnetic and mass isospin breaking.
- Lattice QCD and QED provide a powerful framework for calculating fundamental particle properties.
- The methodology can be extended to precisely determine other particle mass differences.
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