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We study the single longitudinal-spin asymmetry of dihadron production in semi-inclusive deep inelastic scattering process. We consider the collinear picture in which the transverse momentum of the final-state hadron pair is integrated out, such that the sin ϕ R azimuthal asymmetry arises from the coupling h L H ∢ 1 as well as the coupling g 1G ∢. We calculate the unknown twist-3 dihadron fragmentation functionG ∢ using a spectator model which is successful in describing the dihadron production in the unpolarized process. Using the spectator model results for the quark distributions and dihadron fragmentation functions, we estimate the sin ϕ R asymmetry of dihadron production in semi-inclusive deep inelastic scattering at the kinematics of COMPASS and compare it with the COMPASS preliminary data. In addition, the prediction on the sin ϕ R asymmetry at the typical kinematics of the future Electron Ion Collider is also presented. In order to test the reliability of the spectator model estimate, we compare the model result for the distribution h L with the Wandzura-Wilczek approximation for that distribution, and compare H ∢ 1 with the existing parametrization. Although the asymmetry is dominated by the h L H ∢ 1 term, we find that the contribution from the g 1G ∢ term should also be taken into account in certain kinematical region.

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We present a study on the double longitudinal-spin asymmetry of dihadron production in semiinclusive deep inelastic scattering, in which the transverse momentum of the final-state hadron pairs is integrated out. In particular, we investigate the origin of the cos φR azimuthal asymmetry for which we take into account the coupling of the helicity distribution g1 and the twist-3 dihadron fragmentation function D ∢ . We calculate the s-wave and p-wave interference term D ∢ ot in a spectator model. We estimate the cos φR asymmetry at the kinematics of COMPASS which is collecting data on dihadron prouduction in polarized deep inelastic scattering. The prediction of the same asymmetry at JLab 12GeV and a future EIC are also presented. Our study indicates that measuring the cos φR asymmetry in SIDIS may be a ideal way to probe the dihadron fragmentation function D ∢ .

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