DOI 10.1007/s100529900952
Twist-3 contribution to the pion electromagnetic form factor
Fu-Guang Cao1,2 - Yuan-Ben Dai1,2 - Chao-Shang Huang1,2
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
Abstract
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
.
Copyright Springer-Verlag
