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Title: Virtuality Distributions and γγ* -> π0 Transition at Handbag Level

We outline a new approach to transverse momentum dependence in hard processes using as an example the exclusive transition $${\gamma^{*}\gamma \to \pi^{0}}$$ at the handbag level. We start with the coordinate representation for a matrix element $${\langle p |{\cal O}(0,z) |0 \rangle}$$ of a bilocal operator $${{\cal O} (0,z)}$$ describing a hadron with momentum p. Treated as a function of (pz) and z$$^{2}$$, it is parametrized through virtuality distribution amplitude (VDA) Φ (x, σ), with x being Fourier-conjugate to (pz) and σ Laplace-conjugate to z$$^{2}$$. For intervals with z$$^{+}$$ = 0, we introduce the transverse momentum distribution amplitude (TMDA) $${\Ψ (x,k_{\perp})}$$ , and write it in terms of VDA Φ (x, σ). The results of covariant calculations, written in terms of Φ (x, σ) are converted into expressions involving $${\Ψ (x,k_{\perp})}$$ . We propose simple models for soft VDAs/TMDAs, and use them for comparison of handbag results with experimental (BaBar and BELLE) data on the pion transition form factor.
Authors:
 [1]
  1. Old Dominion Univ., Norfolk, VA (United States). Dept. of Physics; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States). Theory Center
Publication Date:
OSTI Identifier:
1223092
Report Number(s):
JLAB-THY--14-1902; DOE/OR/23177--3117
TRN: US1600062
DOE Contract Number:
AC05-06OR23177
Resource Type:
Conference
Resource Relation:
Conference: Light Cone 2014, Raleigh, NC (United States), 26-30 May 2014; Related Information: Also submitted to Few Body Systems, 56(6-9)
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
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; PIONS NEUTRAL; TRANSVERSE MOMENTUM; COMPARATIVE EVALUATIONS; FORM FACTORS; TRANSITION AMPLITUDES; MATRIX ELEMENTS; QUANTUM OPERATORS; PHOTON-PHOTON INTERACTIONS; EXCLUSIVE INTERACTIONS