21–25 Sept 2015
Laboratori Nazionali di Frascati
Europe/Rome timezone

Light-Front Quark Model Analysis of Meson-Photon Transition Form Factor

22 Sept 2015, 17:10
20m
Aula Seminari (LNF, High Energy Buiding no36)

Aula Seminari

LNF, High Energy Buiding no36

Oral contribution PARALLEL SESSION I

Speaker

Prof. Ho-Meoyng Choi (Kyungpook National University)

Description

Hadronic distribution amplitudes (DAs) provide essential information on the QCD interaction of quarks, antiquarks and gluons inside the hadrons and play an essential role in applying QCD to hard exclusive processes such as the pion-photon transition form factor (TTF). As the discrepancy of $Q^2F_{\pi\gamma}(Q^2)$ data between the BaBar and Belle measurements has not been resolved yet, more studies on the meson-photon TTF are called for. In particular, the pion-photon TTF still motivates more theoretical studies using various forms of pion DAs. The general agreement on the analysis of the pion DA is that the broader the pion DA the steeper the slope of $Q^2F_{\pi\gamma}(Q^2)$ as $Q^2$ is getting larger. For instance, the flat pion DA $\phi(x)=1$ shows the agreement with the BaBar data which kept rising over the Belle data as $Q^2$ gets larger. However, the flat pion DA $\phi(x)=1$ is severely different from the twist-2 asymptotic DA $\phi(x)=6x(1-x)$ which has been frequently discussed based on the collinear factorization and QCD scaling. Contrary to the pion-photon TFF,} the subsequent BaBar data for the $(\eta,\eta')\to\gamma^*\gamma$ TFFs have shown the consistency predicted by the perturbative QCD, where the use of flat DA for $\eta$ and $\eta'$ distributions appears strongly disfavored by the datasets of $\eta(\eta')-\gamma$ TFFs. Thus, the careful analysis of $(\eta,\eta')\to\gamma^*\gamma$ transitions is especially important under the circumstance of a prolonged dispute over the pion-photon TFF results. In this talk, we investigate the $P\to\gamma^*\gamma (P=\pi^0,\eta,\eta')$ transitions using the light-front quark model (LFQM) based on the QCD motivated effective LF Hamiltonian. We shall also show both timelike and spacelike TFF using the analytic continuation method of changing $Q^2\to -Q^2$ in the form factor. The $\eta-\eta'$ mixing scheme is analyzed to obtain the optimum values of the $\eta(\eta')-\gamma$ TFFs and compared with the current available experimental data.

Primary author

Prof. Ho-Meoyng Choi (Kyungpook National University)

Co-author

Prof. Chueng Ji (NCSU)

Presentation materials