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, and K. Szabo (Budapest-Marseille-Wuppertal Collaboration)

Phys. Rev. Lett. 111, 252001 – Published 17 December 2013

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 $N_{f} = 2 + 1$ 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.

Received 5 July 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.252001

Authors & Affiliations

Sz. Borsanyi¹, S. Dürr^1,2, Z. Fodor^1,2,3, J. Frison^4,5,†, C. Hoelbling¹, S. D. Katz^3,6, S. Krieg^1,2, Th. Kurth¹, L. Lellouch^4,5, Th. Lippert², A. Portelli^4,5,7,*, A. Ramos^4,5,‡, A. Sastre^4,5, and K. Szabo¹ (Budapest-Marseille-Wuppertal Collaboration)

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

^*Corresponding author. a.portelli@soton.ac.uk
^†Present address: School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
^‡Present address: NIC, DESY Platanenallee 6, D-15738 Zeuthen, Germany.

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Vol. 111, Iss. 25 — 20 December 2013

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