The renormalized next-to-leading-order chiral low-energy constant, $L_{10}^r$, is determined in a complete next-to-next-to-leading-order (NNLO) analysis, using a combination of lattice and continuum data for the flavor $ud$ $V-A$ correlator and results from a recent chiral sum-rule analysis of the flavor-breaking combination of $ud$ and $us$ $V-A$ correlator differences. The analysis also fixes two combinations of NNLO low-energy constants, the determination of which is crucial to the precision achieved for $L_{10}^r$. Using the results of the flavor-breaking chiral $V-A$ sum rule obtained with current versions of the strange hadronic $\tau$ branching fractions as input, we find $L_{10}^r(m_{\rho })=-0.00346(32)$. This result represents the first NNLO determination of $L_{10}^r$, having all inputs under full theoretical and/or experimental control, and the best current precision for this quantity.

• Received 25 April 2014

DOI:https://doi.org/10.1103/PhysRevD.89.094510