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arXiv · hep-ph/0005132

Positivity constraints and flavor dependence of higher twists

J. Soffer·O. V. Teryaev
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Abstract

The positivity bound for the transverse asymmetry $A_2$ may be improved and applied for each quark flavor separately. We use it to test the consistency of twist-two approximation for the transverse spin-dependent ($g_T$) and the longitudinal spin-averaged ($F_L$) structure functions. While it is satisfied in the case of $u$ quarks, it might be violated for $d$ quarks in a region of moderate $x$ because of its negative polarization. We attribute this inconsistency to a stronger twist-three contribution, whose existence found by the QCD sum rule method is a long-standing puzzle.

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J. Soffer, O. V. Teryaev. 2000-05-14. Positivity constraints and flavor dependence of higher twists. https://doi.org/10.1016/s0370-2693(00)00972-2

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