Hard Exclusive Electroproduction of Pseudoscalar Mesons and QCD axial   anomaly
  The hard exclusive electroproduction of $\pi^0,\eta,\eta'$ mesons by the longitudinal photons is considered. We calculate the ratios of the $\pi^0 : \eta : \eta'$ yields for the electroproduction processes off nucleons and deuterons based on the QCD factorization theorem, the low energy QCD chiral dynamics, and the QCD anomaly. Thus investigation of these ratios gives a new way to probe the physics of the spontaneous chiral symmetry breaking. 
Michael I. Eides (Petersburg Nuclear Physics Institute, Russia, and   Pennsylvania State University, USA), Leonid L. Frankfu...