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Paper   IPM / Particles And Accelerator / 11705
School of Particles and Accelerator
  Title:   Rτ and Higgs Decay Width in CORGI Approach, Based on the Leading -b Approximation
1.  Abolfazl Mirjalili
2.  M Akrami Moghestan
  Status:   Published
  Journal: Int. J. Mod. Phys. A
  No.:  12
  Vol.:  26
  Year:  2011
  Pages:   2047-2064
  Supported by:  IPM
We consider Adler D-function for the vector and scalar correlators with recent QCD analysis at N4LO approximation. The portion of perturbative coefficients of these observable containing the leading power of b, the first beta-function coefficient, is resummed to all-orders. The factorial behavior of coefficients allows us to use the Borel transformation to reveal the existent singularities as renormalons. CORGI approach is employed to avoid the renormalisation dependence of the observable.In addition to the CORGI approach, the calculations of the standard perturbative QCD approach which uses the MS scheme with a physical choice of renormalization scale, are also presented. A comparison between the results of the standard and CORGI approaches for Rτ and Higgs decay width is done. The comparison anticipates a better result for the CORGI approach. As an adjunct to these studies, the difference between the all order and fixed order result at N4LO approximation is used to estimate the uncertainty in αs(MZ2) extracted from Rτ measurements. We find at N4LO approximation a smaller uncertainty with respect to the previous result which has been done at N2LO approximation.

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