Determination of light quark masses from η→3π0

We provide a model-independent determination of the quantity B0(md-mu). Our approach rests only on chiral symmetry and data from the decay of the eta into three neutral pions. Since the low-energy prediction at next-to-leading order fails to reproduce the experimental results, we keep the strong interaction correction as an unknown parameter. As a first step, we relate this parameter to the quark mass difference using data from the Dalitz plot. A similar relation is obtained using data from the decay width. Combining both relations we obtain B0(md-mu)=(4495±440) MeV2. The preceding value, combined with lattice determinations, leads to the values mu(2 GeV)=(2.9±0.8) MeV and md(2 GeV)=(4.7±0.8) MeV.