Order alpha**4(s) QCD Corrections to Z and tau Decays
Jan, 20085 pages
Published in:
- Phys.Rev.Lett. 101 (2008) 012002
e-Print:
- 0801.1821 [hep-ph]
Report number:
- SFB-CPP-08-04,
- TTP08-01
View in:
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Abstract: (arXiv)
Using recently developed methods for the evaluation of five-loop amplitudes in perturbative QCD, corrections of order alpha_s^4 for the cross section of electron-positron annihilation into hadrons and for the decay rates of the Z-boson and the tau-lepton into hadrons are evaluated. The new terms lead to a significant stabilization of the perturbative series, to a reduction of the theory uncertainly in the strong coupling constant alpha_s, as extracted from these measurements, and to a small shift of the central value, moving two central values closer together. The agreement between two values of alpha_s measured at vastly different energies constitutes a striking test of asymptotic freedom. Combining the results from Z and tau decays we find alpha_s(M_Z)=0.1198 \pm 0.0015 as one of the most precise and presently only NNNLO result for the strong coupling constant.- 13.35.Dx
- 13.85.Lg
- 12.38.Bx
- electron positron: annihilation
- hadron: electroproduction
- Z0: hadronic decay
- Z0: width
- tau: hadronic decay
- tau: width
- cross section
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