Expansion functions in perturbative QCD and the determination of α.sub.s./sub.(M.sub.τ./sub..sup.2./sup.)

0375194 - FZÚ 2012 RIV US eng J - Journal Article
Caprini, I. - Fischer, Jan
Expansion functions in perturbative QCD and the determination of α_s(M_τ²).
Physical Review D: Particles, Fields, Gravitation and Cosmology. Roč. 84, č. 5 (2011), 054019/1-054019/15. ISSN 1550-7998
R&D Projects: GA MŠMT LA08015
Institutional research plan: CEZ:AV0Z10100502
Keywords : quantum chromodynamics, * conformal mapping * tau lepton decay
Subject RIV: BF - Elementary Particles and High Energy Physics
Impact factor: 4.558, year: 2011

The conventional series in powers of the coupling in perturbative QCD have zero radius of convergence and fail to repreduce the singularity of the QCD correlators like the Adler function at /alpha_s=0. Using the technique of conformal mapping of the Borel plane combined with the "softening" of the leading singularities, we define the set of new expansion functions which resemble the expanded correlator and share the same singularity at zero coupling. Several conformal mappings and ways of implementing the known nature of the first branch points of the Adler function in the Borel plane are investigated both in the CIPT and in the FOPT versions of the renormalization group resummation. We prove remarkable convergence properties of a set of new CI expansions and use them to determine the strong coupling from the hadronic tau decay width.
Permanent Link: http://hdl.handle.net/11104/0207924