On the Physical Relevance of the Study of gamma* gamma -> pi pi at small t and large Q2

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We discuss the relevance of a dedicated measurement of exclusive production of a pair of neutral pions in a hard {gamma}*{gamma} scattering at small momentum transfer. In this case, the virtuality of one photon provides us with a hard scale in the process, enabling us to perform a QCD calculation of this reaction rate using the concept of Transition Distribution Amplitudes (TDA). Those are related by sum rules to the pion axial form factor F{sub A}{sup {pi}} and, as a direct consequence, a cross-section measurement of this process at intense beam electron-positron colliders such as CLEO, KEK-B and PEP-II, or ... continued below

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7 pages

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Lansberg, J.P.; /SLAC; Pire, B.; /Ecole Polytechnique, CPHT; Szymanowski, L. & /Warsaw, Inst. Nucl. Studies August 26, 2010.

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We discuss the relevance of a dedicated measurement of exclusive production of a pair of neutral pions in a hard {gamma}*{gamma} scattering at small momentum transfer. In this case, the virtuality of one photon provides us with a hard scale in the process, enabling us to perform a QCD calculation of this reaction rate using the concept of Transition Distribution Amplitudes (TDA). Those are related by sum rules to the pion axial form factor F{sub A}{sup {pi}} and, as a direct consequence, a cross-section measurement of this process at intense beam electron-positron colliders such as CLEO, KEK-B and PEP-II, or Super-B would provide us with a unique measurement of the neutral pion axial form factor F{sub A}{sup {pi}0} at small scale. We believe that our models for the photon to meson transition distribution amplitudes are sufficiently constrained to give reasonable orders of magnitude for the estimated cross sections. Cross sections are large enough for quantitative studies to be performed at high luminosity e{sup +}e{sup -} colliders. After verifying the scaling and the {phi} independence of the cross section, one should be able to measure these new hadronic matrix elements, and thus open a new gate to the understanding of the hadronic structure. In particular, we argued here that the study of {gamma}*{gamma} {yields} {pi}{sup 0}{pi}{sup 0} in the TDA regime could provide with a unique experimental measurement of the {pi}{sup 0} axial form factor.

Physical Description

7 pages

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  • Invited talk at Photon 2009: International Conference on the Structure and Interactions of the Photon: 18th International Workshop on Photon-Photon Collisions: International Workshop on High Energy Photon Linear Colliders, Hamburg, Germany, 11-15 May 2009

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  • Report No.: SLAC-PUB-13726
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 992453
  • Archival Resource Key: ark:/67531/metadc1014182

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  • August 26, 2010

Added to The UNT Digital Library

  • Oct. 14, 2017, 8:36 a.m.

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  • Nov. 3, 2017, 1:28 p.m.

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Lansberg, J.P.; /SLAC; Pire, B.; /Ecole Polytechnique, CPHT; Szymanowski, L. & /Warsaw, Inst. Nucl. Studies. On the Physical Relevance of the Study of gamma* gamma -> pi pi at small t and large Q2, article, August 26, 2010; [California]. (digital.library.unt.edu/ark:/67531/metadc1014182/: accessed October 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.