$\alpha_s(m_\tau)$ from an improved vector isovector spectral function
December 01, 2022
We discuss a new determination of the strong coupling at the $\tau$-mass scale, $\alpha_s(m_\tau^2)$, based on a new vector isovector spectral function, which combines ALEPH and OPAL spectra for the dominant $2\pi$ and $4\pi$ decay channels with estimates for several sub-leading contributions obtained using CVC from recently measured electroproduction cross-sections, as well as results for $\tau\to K^- K^0\nu_\tau$ obtained by BaBar. This fully inclusive vector isovector spectral function is entirely based on experimental data, and no longer relies on Monte Carlo input for any of the sub-leading modes. We obtain $\alpha_s(m_\tau)=0.3077\pm 0.0075$, corresponding to $\alpha_s(m_Z)=0.1171\pm 0.0010$.
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