Theoretical progress on the V_us determination from tau decays
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.
Keywords
Cite
@article{arxiv.0709.0282,
title = {Theoretical progress on the V_us determination from tau decays},
author = {Elvira Gamiz and Matthias Jamin and Antonio Pich and Joaquim Prades and Felix Schwab},
journal= {arXiv preprint arXiv:0709.0282},
year = {2008}
}
Comments
Invited talk at the Kaon International Conference -KAON'07- (Frascati, Italy, May 21-25, 2007)