17-24 July 2013
KTH and Stockholm University Campus
Europe/Stockholm timezone

Strong coupling from the tau-lepton hadronic width

18 Jul 2013, 09:15
E1 (KTH Campus)


KTH Campus

Talk presentation QCD QCD


gauhar abbas (IMSc Chennai, India)


We determine the strong coupling constant $\alpha_s$ from the $\tau$ hadronic width using renormalization group summed expansion of the QCD Adler function. The main theoretical uncertainty in the extraction of $\alpha_s$ is due to the way in which renormalization group invariance is implemented and the yet uncalculated higher order terms in the QCD perturbative series. We show that new expansion exhibits nice renormalization group improvement and the behaviour of the series is similar to standard CIPT expansion. We further study the convergence properties of this expansion improved by Borel transformation and the analytical continuation in the Borel plane. We find that the new, non-power expansions for different conformal mappings have remarkable convergence. Finally we provide the value of strong coupling $\alpha_s$ using the new, non-power perturbative expansions which is $\alpha_s(M_\tau^2)= 0.3189^{+ 0.0145}_{-0.0115}$, which translates to $ \alpha_s(M_Z^2)= 0.1184^{+0.0018}_{-0.0015}$.

Primary author

gauhar abbas (IMSc Chennai, India)


Balasubramanian Ananthanarayan (Indian Institute of Science) Irinel Caprini (Horia Hulubei National Institute of Physics and Nuclear Enginee) Jan Fischer (Institute of Physics)

Presentation Materials