Transverse structure function in the factorisation method

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Deep Inelastic scattering experiments using transversely polarised targets yield information on the structure function g₂. By means of a free-field analysis, we study the operator structure of g₂ and demonstrate the need for retaining the twist three mass terms in order to maintain current-conservation. We show that the structure function gₜ=g₁+g₂ has a much simpler operator structure as compared to g₂, in spite of the fact that, like g₂, gₜ has a twist-three component. We demonstrate factorisation of the hadronic tensor into hard and soft parts for the case of gₜ. We show that the first moment of the gluonic contribution to gₜ vanishes, and discuss possible physical applications.