Form factors and QCD in spacelike and timelike regions

A. P. Bakulev, A. V. Radyushkin, and N. G. Stefanis
Phys. Rev. D 62, 113001 – Published 17 October 2000
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Abstract

We analyze the basic hard exclusive processes, the πγ*γ-transition and the pion and nucleon electromagnetic form factors, and discuss the analytic continuation of QCD formulas from the spacelike q2<0 to the timelike region q2>0 of the relevant momentum transfers. We describe the construction of the timelike version of the coupling constant αs. We show that due to the analytic continuation of the collinear logarithms, each eigenfunction of the evolution equation acquires a phase factor and investigate the resulting interference effects which are shown to be very small. We find no sources for the K-factor-type enhancements in the perturbative QCD contribution to the hadronic form factors. To study the soft part of the pion electromagnetic form factor, we use a QCD sum rule inspired model and show that there are noncanceling Sudakov double logarithms which result in a K-factor-type enhancement in the timelike region.

  • Received 19 June 2000

DOI:https://doi.org/10.1103/PhysRevD.62.113001

©2000 American Physical Society

Authors & Affiliations

A. P. Bakulev

  • Bogolyubov Laboratory of Theoretical Physics, JINR, Dubna, 141980 Russia

A. V. Radyushkin*

  • Physics Department, Old Dominion University, Norfolk, Virginia 23529
  • Theory Group, Jefferson Lab, Newport News, Virginia 23606

N. G. Stefanis

  • Institut für Theoretische Physik II, Ruhr-Universität Bochum, D-44780 Bochum, Germany

  • *Also at Laboratory of Theoretical Physics, JINR, Dubna, 141980 Russia.

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Vol. 62, Iss. 11 — 1 December 2000

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