The cos⁡2ϕ azimuthal asymmetry in e+e− → π+π−X process

We study the transverse momentum dependent cos⁡2ϕ azimuthal asymmetry in e+e−→π+π−X process. Particularly, we take into account the contribution of the acoplanarity to the azimuthal asymmetry due to the digluon radiation correction effect. As a comparison, we also consider the contribution from Collins effect within the transverse momentum dependent factorization. We perform the calculation at s=10.58, accessible at Belle and BaBar Collaborations; and we choose in the Gottfried-Jackson frame, which is more convenient in comparing theoretical calculations with current experimental measurement. In the calculation we apply a recent parametrization on the Collins function. We adopt the Drell-Yan parametrization for the mean value of cos⁡2ϕ1. We find that in the region qT≪Q region, the asymmetry is dominated by the Collins effect, while the acoplanarity effect dominates in the large qT region (qT/Q>0.5) and is negligible in the small qT region. In the intermediate region the two contributions are comparable.