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arXiv · 0709.0282

Theoretical progress on the V_us determination from tau decays

Elvira Gamiz·Matthias Jamin·Antonio Pich·Joaquim Prades·Felix Schwab
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Abstract

A very precise determination of V_us can be obtained from the semi-inclusive hadronic decay width of the tau lepton into final states with strangeness. The ratio of the Cabibbo-suppressed and Cabibbo-allowed tau decay widths directly measures (V_us/V_ud)^2, up to very small SU(3)-breaking corrections which can be theoretically estimated with the needed accuracy. Together with previous LEP and CLEO data, the recent measurements by Babar and Belle of some Cabibbo-suppressed tau decays imply V_us= 0.2165 +- 0.0026_exp +- 0.0005_th, which is already competitive with the standard extraction from K_l3 decays. The uncertainty is largely dominated by experimental errors and should be easily reduced with the high statistics of the B factories, providing the most accurate determination of this parameter. A 1% experimental precision on the Cabibbo-suppressed tau decay width would translate into a 0.6% uncertainty on V_us.

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Elvira Gamiz, Matthias Jamin, Antonio Pich, Joaquim Prades, Felix Schwab. 2007-09-03. Theoretical progress on the V_us determination from tau decays. https://arxiv.org/abs/0709.0282

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