Isospin violation in QCD sum rules for baryons

We thoroughly analyze isospin-violating effects in QCD sum rules for the masses of nucleons, $\Sigma$, and $\Xi$ hyperons. After comparing with experimental mass splittings in isotopic multiplets, we obtain for the isospin breaking in the quark condensate $\frac{〈0|\overline{u}u-\overline{d}d|0\mathrm{}〉}{〈0\left|\overline{u}u\right|0\mathrm{}〉}=(2\mathrm{}\pm 1)\times {10}^{-3\mathrm{}}$, a value significantly smaller than the one usually adopted. We present arguments in favor of our result and critically analyze previous estimates. The value of the quark mass difference $m_d-m_u=3.0\mathrm{}\pm 1.0$ MeV (at normalization point $\overline{\mu }=0.5\mathrm{}$ GeV) is also determined.