The Cos2 Phi Azimuthal Asymmetry In E(+)E(-) -> Pi(+)Pi X- Process

We study the transverse momentum dependent cos2 phi azimuthal asymmetry in e(+)e(-) -> pi(+)pi 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 root 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 cos2 phi(1). We find that in the region q(T) << Q region, the asymmetry is dominated by the Collins effect, while the acoplanarity effect dominates in the large q(T) region (q(T)/Q>0.5) and is negligible in the small q(T) region. In the intermediate region the two contributions are comparable. (C) 2020 The Author(s). Published by Elsevier B.V.