Hard exclusive two photon processes in QCD

Abstract

This is a short review of some hard two-photon processes: $$\begin{gathered} a)\gamma \gamma \to {\overline{P}}_1{P}_2,{\overline{P}}_1{P}_2=\{{\pi }^{+}{\pi }^{-},K^{+}{K}^{-},K_S{K}_S,{\pi }^o{\pi }^o,{\pi }^o\eta \}, \\ b)\gamma \gamma \to V_1{V}_2,V_1{V}_2=\{{\rho }^o{\rho }^o,\varphi \varphi ,\omega \varphi ,\omega \omega \}, \\ c)\gamma \gamma \to \mathrm{baryon}-\mathrm{antibaryon}, \\ d){\gamma }^{\ast }\gamma \to P^o,P^o=\{{\pi }^o,\eta ,{\eta }^{\prime },{\eta }_c\} \end{gathered}$$. The available experimental data are presented. A number of theoretical approaches to calculation of these processes is described, both those based mainly on QCD and more phenomenological (the handbag model, the diquark model, etc). Some theoretical questions tightly connected with this subject are discussed, in particular: the applications of various types of QCD sum rules, the endpoint behavior of the leading twist meson wave functions, etc.

58 pages, 38 figures, review article; v2: a large number of minor corrections

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Cited by in corpus (13)

• Insights into the Emergence of Mass from Studies of Pion and Kaon Structure
• Lattice calculation of the pion transition form factor ${\pi }^0\to {\gamma }^{\ast }{\gamma }^{\ast }$
• Second Moment of the Pion Light-cone Distribution Amplitude from Lattice QCD
• gamma-UPC: Automated generation of exclusive photon-photon processes in ultraperipheral proton and nuclear collisions with varying form factors
• Two-photon transitions of charmonia on the light front
• The ${\gamma }^{\ast }{\gamma }^{\ast }\to {\eta }_c(1S,2S)$ transition form factors for spacelike photons
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