Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
2010-05-24
Phys.Rev.D82:093007,2010
Physics
High Energy Physics
High Energy Physics - Phenomenology
11 pages, 3 figures
Scientific paper
10.1103/PhysRevD.82.093007
The semihadronic tau decay width allows a clean extraction of the strong coupling constant at low energies. We present a modification of the standard "contour improved" method based on a derivative expansion of the Adler function. The approach eliminates ambiguities coming from the existence of different integral expressions for the semihadronic tau decay ratio. Compared to the standard method, renormalization scale dependence is by more than a factor two weaker in modified contour improved perturbation theory. The last term of the expansion is reduced, and renormalization scheme dependence remains approximately equal. The extracted QCD coupling at the tau mass scale is by 2$%$ lower than the "contour improved" value. We find $\alpha_s(M_Z^2)=0.1211\pm 0.0010$.
Cvetic Gorazd
Loewe Marcelo
Martinez Cristian
Valenzuela Cristian
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