Isospin splittings in the light-baryon octet from lattice QCD and QED

Sz Borsanyi; S Dürr; Z Fodor; J Frison; C Hoelbling; S D Katz; S Krieg; Th Kurth; L Lellouch; Th Lippert; A Portelli; A Ramos; A Sastre; K Szabo; Budapest-Marseille-Wuppertal Collaboration

doi:10.1103/PhysRevLett.111.252001

Isospin splittings in the light-baryon octet from lattice QCD and QED

Phys Rev Lett. 2013 Dec 20;111(25):252001. doi: 10.1103/PhysRevLett.111.252001. Epub 2013 Dec 17.

Authors

Sz Borsanyi¹, S Dürr², Z Fodor³, J Frison⁴, C Hoelbling¹, S D Katz⁵, S Krieg², Th Kurth¹, L Lellouch⁴, Th Lippert⁶, A Portelli⁷, A Ramos⁴, A Sastre⁴, K Szabo¹; Budapest-Marseille-Wuppertal Collaboration

Affiliations

¹ Department of Physics, Wuppertal University, Gaussstrasse 20, D-42119 Wuppertal, Germany.
² Department of Physics, Wuppertal University, Gaussstrasse 20, D-42119 Wuppertal, Germany and IAS/JSC, Forschungszentrum Jülich, D-52425 Jülich, Germany.
³ Department of Physics, Wuppertal University, Gaussstrasse 20, D-42119 Wuppertal, Germany and IAS/JSC, Forschungszentrum Jülich, D-52425 Jülich, Germany and Institute for Theoretical Physics, Eötvös University, Pázmány Peter sétany 1/A, H-1117 Budapest, Hungary.
⁴ Aix-Marseille Université, CNRS, CPT, UMR 7332, 13288 Marseille, France and Université de Toulon, CNRS, CPT, UMR 7332, 83957 La Garde, France.
⁵ Institute for Theoretical Physics, Eötvös University, Pázmány Peter sétany 1/A, H-1117 Budapest, Hungary and MTA-ELTE Lendület Lattice Gauge Theory Research Group, H-1117 Budapest, Hungary.
⁶ IAS/JSC, Forschungszentrum Jülich, D-52425 Jülich, Germany.
⁷ Aix-Marseille Université, CNRS, CPT, UMR 7332, 13288 Marseille, France and Université de Toulon, CNRS, CPT, UMR 7332, 83957 La Garde, France and School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, United Kingdom.

PMID: 24483739
DOI: 10.1103/PhysRevLett.111.252001

Abstract

While electromagnetic and up-down quark mass difference effects on octet baryon masses are very small, they have important consequences. The stability of the hydrogen atom against beta decay is a prominent example. Here, we include these effects by adding them to valence quarks in a lattice QCD calculation based on Nf=2+1 simulations with five lattice spacings down to 0.054 fm, lattice sizes up to 6 fm, and average up-down quark masses all the way down to their physical value. This allows us to gain control over all systematic errors, except for the one associated with neglecting electromagnetism in the sea. We compute the octet baryon isomultiplet mass splittings, as well as the individual contributions from electromagnetism and the up-down quark mass difference. Our results for the total splittings are in good agreement with experiment.