Exclusive high-$Q^2$ electroproduction: light-cone wave functions and electromagnetic form factors of mesons,

Abstract

We apply the light-cone technique to electroproduction reaction $ep\to e\pi^+n$ long considered as a means of measuring the electromagnetic form factor of the pion. We show that the interpretation of the long-standing puzzle of large transverse cross section ($\sigma_T$) in terms of the $\gamma^*\rho\to \pi$ transition on the $\rho$ mesons in the light-cone proton is possible, but requires quite a slow decrease of the $F_{\rho\pi}(\q2)$ form factor. This interpretation can be tested in the related $ep\to e\pi^0p$ reaction. Corrections which are due to the final-state meson-baryon interactions (FSI) are evaluated and are shown to amount to a $25\%$ effect at moderately large $\q2$. Vanishing FSI with increasing $Q^2$ - the color transparency phenomenon - is shown to be very strong.