Twist-3 contribution to the pion electromagnetic form factor
1 CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, P.R. China
2 Institute of Theoretical Physics, Academia Sinica, P.O. Box 2735, Beijing 100080, P.R. China
Received: 23 March 1998 / Published online: 3 November 1999
Non-leading contribution to the pion electromagnetic form factor which comes from the pion twist-3 wave function is analyzed in the modified hard scattering approach (MHSA) proposed by Li and Sterman. This contribution is enhanced significantly due to bound state effect (the twist-3 wave function is independent of the fractional momentum carried by the parton and has a large factor with being the pion meson mass and m0 being the mean u- and d-quark masses). Consequently, although it is suppressed by the factor 1/Q2, the twist-3 contribution is comparable with and even larger than the leading twist (twist-2) contribution at intermediate energy region of Q2 being .