Double Spin Asymmetries $A_{LT}^{\cosϕ_S}$ and $A_{LT}^{\cos(2ϕ_h -ϕ_S)}$ in semi-inclusive DIS

Wenjuan Mao; Zhun Lu; Bo-Qiang Ma; Ivan Schmidt

doi:10.1103/PhysRevD.91.034029

paper

Double Spin Asymmetries $A_{L T}^{c o s ϕ_{S}}$ and $A_{L T}^{c o s (2 ϕ_{h} - ϕ_{S})}$ in semi-inclusive DIS

arXiv:1412.7390 · doi:10.1103/PhysRevD.91.034029

Abstract

We investigate the double spin asymmetries of pion production in semi-inclusive deep inelastic scattering with a longitudinal polarized beam off a transversely polarized proton target. Particularly, we consider the $cos ϕ_{S}$ and $cos (2 ϕ_{h} - ϕ_{S})$ modulations, which can be interpreted by the convolution of the twist-3 transverse momentum dependent distributions and twist-2 fragmentation functions. Three different origins are taken into account simultaneously for each asymmetry: the $g_{T} D_{1}$ term, the $e_{T} H_{1}^{⊥}$ term, and the $e_{T}^{⊥} H_{1}^{⊥}$ term in the $cos ϕ_{S}$ asymmetry; and the $g_{T}^{⊥} D_{1}$ term, the $e_{T} H_{1}^{⊥}$ term, and the $e_{T}^{⊥} H_{1}^{⊥}$ term in the $cos (2 ϕ_{h} - ϕ_{S})$ asymmetry. We calculate the four twist-3 distributions $g_{T} (x, k_{T}^{2})$ , $g_{T}^{⊥} (x, k_{T}^{2})$ , $e_{T} (x, k_{T}^{2})$ , and $e_{T}^{⊥} (x, k_{T}^{2})$ in a spectator-diquark model including vector diquarks. Then we predict the two corresponding asymmetries for charged and neutral pions at the kinematics of HERMES, JLab, and COMPASS for the first time. The numerical estimates indicate that the two different angular-dependence asymmetries are sizable by several percent at HERMES and JLab, and the $cos ϕ_{S}$ asymmetry has a strong dependence on the Bjorken $x$ . Our predictions also show that the dominant contribution to the $cos ϕ_{S}$ asymmetry comes from the $g_{T} D_{1}$ term, while the $g_{T}^{⊥} D_{1}$ term gives the main contribution to the $cos (2 ϕ_{h} - ϕ_{S})$ asymmetry; the other two $T$ -odd terms almost give negligible contributions. In particular, the $cos (2 ϕ_{h} - ϕ_{S})$ asymmetry provides a unique opportunity to probe the distribution $g_{T}^{⊥}$ .

arXiv commentminor revision, match the published version in PRD. arXiv admin note: text overlap with arXiv:1405.3876

Double Spin Asymmetries $A_{L T}^{c o s ϕ_{S}}$ and $A_{L T}^{c o s (2 ϕ_{h} - ϕ_{S})}$ in semi-inclusive DIS

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Double Spin Asymmetries ALTcosϕS​​ and ALTcos(2ϕh​−ϕS​)​ in semi-inclusive DIS

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Double Spin Asymmetries $A_{L T}^{c o s ϕ_{S}}$ and $A_{L T}^{c o s (2 ϕ_{h} - ϕ_{S})}$ in semi-inclusive DIS