Abstract
In this paper we study the double longitudinal spin asymmetry of dihadron production in semi-inclusive deep inelastic scattering (SIDIS). We calculate a unknown twist-3 dihadron fragmentation function $\widetilde{D}^\sphericalangle$ within a spectator model which has been used successfully in describing the dihadron production in both the unpolarized and the single polarized processes. The collinear picture, in which the transverse momentum of the final state hadron pair is integrated out, has been considered. The $\cos\phi_R$ azimuthal asymmetry arises from the coupling $e_L H_1^\sphericalangle$ and the coupling $g_1 \widetilde{D}^\sphericalangle$ is studied. We estimate the $\cos\phi_R$ asymmetry at the kinematics of COMPASS and compare with the data. The prediction at the future Electron Ion Collider (EIC) has also been presented.
Highlights
Azimuthal asymmetries in semiinclusive deep inelastic scattering (SIDIS) are key observables to investigate the spin-dependent substructure of the nucleon
Before working out the dihadron fragmentation functions (DiFFs) D ∢ot in the spectator model, we briefly review the calculation of twist-two DiFFs D1;oo and H∢1;ot given by Ref. [20]
In order to fix the parameters of the spectator model, the authors of Ref. [20] compare it with the output of the PYTHIA event generator adopted for HERMES
Summary
Azimuthal asymmetries in SIDIS are key observables to investigate the spin-dependent substructure of the nucleon. Physicists started to focus on these functions by searching for a mechanism to extract the chiral-odd transversity distribution in an alternative and technically simpler way than the Collins effect [11] In this mechanism, the chiral-odd DiFF H∢1 [7,12] plays an important role in accessing transversity distribution h1, as it couples with h1 at the leading-twist level in the collinear factorization. In principle two source contribute to the cos φR asymmetry, one is the coupling of the twist-three distribution eL and the twist-two DiFF H∢1 , the other is the twist-three DiFF D ∢ combined with the helicity distribution eg1L.ðxTÞhe1⁄4fRordm2eprTceoLnðtxri;bpuTtiÞon1⁄4v0an[i3s1h]essimncoedtehleinTd-eopdednPdDenFtlyis: forbidden by time-reversal invariance This is because after pT integration the Wilson line in the nonlocal quark bilinear expression, which defines the PDF, connects the quark fields along a straight line on the light cone.
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