Brodsky-Lepage-Mackenzie scale for the pion transition form factor

Melić, Blaženka; Nižić, Bene; Passek-Kumerički, Kornelija (2002) Brodsky-Lepage-Mackenzie scale for the pion transition form factor. Physical Review D, 65 (5). 053020-1-053020-33. ISSN 0556-2821

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Abstract

The next-to-leading order (NLO) Brodsky-Lepage-Mackenzie (BLM) scale for the pion transition form factor is determined. To achieve that, a consistent calculation up to n(f)-proportional next-to-next-to-leading order contributions to both the hard-scattering amplitude and the perturbatively calculable part of the pion distribution amplitude is performed. By combining and matching the results obtained for these two amplitudes, a proper cancellation of collinear singularities is established and the gamma(s) ambiguity problem (related to the use of the dimensional regularization method) is resolved by using the naive-gamma(s) as well as the 't Hooft-Veltman (HV) schemes. It is demonstrated that the prediction for the pion transition form factor is independent of the factorization scale mu(F)(2) at every order in the strong coupling constant, making it possible to use the simplest choice mu(F)(2) = Q(2) at the intermediate steps of the calculation. Assuming the pion asymptotic distribution amplitude and working in the (MS) over bar scheme, we find the BLM scale to be mu(K)(2) = mu(BLM)(2)approximate toQ(2)/9. Based an the same distribution, the complete NLO prediction for the pion transition form factor is calculated in the alpha(V) definition of the QCD coupling renormalized at mu(R)(2) = mu(V)(2) = e(5/3) mu(BLM)(2)approximate toQ(2)/2. It is in good agreement with the presently available experimental data.

Item Type:	Article
Uncontrolled Keywords:	qcd sum-rules; perturbative quantum chromodynamics; large momentum-transfer; exclusive processes; leading-order; asymptotic-behavior; dimensional regularization; distribution amplitude; factor gamma-gamma-asterisk->pi(0); transverse-momentum
Subjects:	NATURAL SCIENCES > Physics NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Divisions:	Theoretical Physics Division
Projects:	Project title Project leader Project code Project type Temeljne interakcije u fizici elementarnih čestica i kozmologiji Branko Guberina 0098002 MZOS
Depositing User:	Blaženka Melić
Date Deposited:	27 Aug 2013 10:21
URI:	http://fulir.irb.hr/id/eprint/569
DOI:	10.1103/PhysRevD.65.053020

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