skip to main content

Title: Pion Electromagnetic Form Factor in Virtuality Distribution Formalism

We discuss two applications of the {\it Virtuality Distribution Amplitudes} (VDA) formalism developed in our recent papers. We start with an overview of the main properties of the pion distribution amplitude emphasizing the quantitative measures of its width, and possibility to access them through the pion transition form factor studies. We formulate the basic concepts of the VDA approach and introduce the pion {\it transverse momentum distribution amplitude} (TMDA) which plays, in a covariant Lagrangian formulation, a role similar to that of the pion wave function in the 3-dimensional Hamiltonian light-front approach. We propose simple factorized models for soft TMDAs, and use them to describe existing data on the pion transition form factor, thus fixing the scale determining the size of the transverse-momentum effects. Finally, we apply the VDA approach to the one-gluon exchange contribution for the pion electromagnetic form factor. We observe a very late $$Q^2 \gtrsim 20$$ GeV$^2$ onset of transition to the asymptotic pQCD predictions and show that in the $$Q^2 \lesssim 10$$ GeV$^2$ region there is essentially no sensitivity to the shape of the pion distribution amplitude. Furthermore, the magnitude of the one-gluon exchange contribution in this region is estimated to be an order of magnitude below the Jefferson Lab data, thus leaving the Feynman mechanism as the only one relevant to the pion electromagnetic form factor behavior for accessible $Q^2$.
  1. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion Univ., Norfolk, VA (United States)
Publication Date:
OSTI Identifier:
Report Number(s):
JLAB-THY-15-2150; DOE/OR/23177-3577; arXiv:1510.03388
DOE Contract Number:
Resource Type:
Resource Relation:
Journal Name: Proceedings of Science; Journal Volume: QCDEV2015; Conference: QCD Evolution Workshop (QCD 2015), 26-30 May 2015. Newport News, VA, USA
Research Org:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States