Time-like pion electromagnetic form factors in $k_T$ factorization with the Next-to-leading-order twist-3 contribution

Abstract

We calculate the time-like pion electromagnetic form factor in the $k_T$ factorization formalism with the inclusion of the next-to-leading-order(NLO) corrections to the leading-twist and sub-leading-twist contributions. It's found that the total NLO correction can enhance (reduce) the magnitude (strong phase) of the leading order form factor by $20\%-30\%$ ( $<15^o$) in the considered invariant mass squared $q^2>5$ GeV${}^2$, and the NLO twist-3 correction play the key role to narrow the gap between the pQCD predictions and the measured values for the time-like pion electromagnetic form factor.

Comments: 11 pags, 4 figures