Abstract
In a previous Letter [Borsanyi et al., Phys. Rev. Lett. 111, 252001
(2013)] we determined the isospin mass splittings of the baryon octet
from a lattice calculation based on Nf=2 +1 QCD simulations
to which QED effects have been added in a partially quenched setup.
Using the same data we determine here the corrections to Dashen's
theorem and the individual up and down quark masses. Our ensembles
include 5 lattice spacings down to 0.054 fm, lattice sizes up to 6 fm,
and average updown quark masses all the way down to their physical
value. For the parameter which quantifies violations to Dashen's
theorem, we obtain ɛ =0.73 (2 )(5 )(17 ), where the first error
is statistical, the second is systematic, and the third is an estimate
of the QED quenching error. For the light quark masses we obtain,
mu=2.27 (6 )(5 )(4 ) and md=4.67 (6 )(5 )(4 ) MeV
in the modified minimal subtraction scheme at 2 G e V and the isospin
breaking ratios mu/md=0.485 (11 )(8 )(14 ), R
=38.2 (1.1 )(0.8 )(1.4 ), and Q =23.4 (0.4 )(0.3 )(0.4 ). Our results
exclude the mu=0 solution to the strong C P problem by more
than 24 standard deviations.
Original language  English 

Pages (fromto)  82001 
Journal  Physical Review Letters 
Volume  117 
Issue number  8 
DOIs  
Publication status  Published  15 Aug 2016 
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Profiles

Antonin Portelli
 School of Physics and Astronomy  Chancellor's Fellow: Computation / Big Data & Reader
Person: Academic: Research Active