Abstract
We analyze longitudinal beam and target single-spin asymmetries in semi-inclusive deep inelastic scattering and in jet deep inelastic scattering, including all possible twist-3 contributions as well as quark mass corrections. We take into account the path-ordered exponential in the soft correlators and show that it leads to the introduction of a new distribution and a new fragmentation function contributing to the asymmetries.
Highlights
Longitudinal beam and target single-spin asymmetries have been at the center of the attention lately, since they have been measured by the HERMES and CLAS experimental Collaborations [1,2,3,4] and more measurements are planned
In this Letter we presented a complete study of the semi-inclusive DIS beam and target longitudinal spin asymmetries, ALU and AUL, up to subleading order in 1/Q, including transverse momentum dependent and T-odd distribution and fragmentation functions
In order to be sure to include all contributions, we performed a new analysis of the quark correlation functions, on the basis of what was suggested in Ref. [19], where the necessity to include the direction of the gauge link as an independent degree of freedom in the decomposition of the correlation function was advocated
Summary
Longitudinal beam and target single-spin asymmetries have been at the center of the attention lately, since they have been measured by the HERMES and CLAS experimental Collaborations [1,2,3,4] and more measurements are planned. An exhaustive treatment of the contributions of T-odd distribution functions has not been carried out completely so far, especially up to subleading order in an expansion in 1/Q, Q2 being the virtuality of the incident photon and the only hard scale of the process, and including quark mass corrections It is the purpose of the present work to describe the longitudinal beam and target spin asymmetries in a complete way in terms of leading and subleading twist distribution and fragmentation functions. The inclusion of the gauge link in the proper definition of the correlator, introduces a dependence on the light cone vector, n−, that defines the direction along which the path-ordered exponential is running The inclusion of this new degree of freedom spoils the Lorentz-invariance relations among distribution functions as pointed out in Refs. Evidence—either from experiments or from model calculations—for the existence of these new functions could support the necessity of introducing the gauge-link direction in the decomposition of the correlator
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