Twist decomposition of nonlocal light-cone operators II: General tensors of 2nd rank

A group theoretical procedure, introduced earlier in [6], to decompose bilocal light–ray operators into (harmonic) operators of definite twist is applied to the case of arbitrary 2nd rank tensors. As a generic example the bilocal gluon operator is considered which gets contributions of twist–2 up to twist–6 from four different symmetry classes characterized by corresponding Young tableaux; also the twist decomposition of the related vector and scalar operators is considered. In addition, we extend these results to various trilocal light–ray operators, like the Shuryak-Vainshtein, the three– gluon and the four–quark operators, which are required for the consideration of higher–twist distribution amplitudes. The present results rely on the knowledge of harmonic tensor polynomials of any order n which have been determined up to the case of 2nd rank symmetric tensor for arbitrary space-time dimension. e-mail: [email protected] e-mail: [email protected]