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We present FEYNCALC 9.3, a new stable version of a powerful and versatile MATHEMAT-ICA package for symbolic quantum field theory (QFT) calculations. Some interesting new features such as highly improved interoperability with other packages, automatic extraction of the ultraviolet divergent parts of 1-loop integrals, support for amplitudes with Majorana fermions and γ-matrices with explicit Dirac indices are explained in detail. Furthermore, we discuss some common problems and misunderstandings that may arise in the daily usage of the package, providing explanations and workarounds.

We present the calculation of the two-loop spin splitting functions P (1) ij (x) (i, j = q, g) contributing to the next-to-leading order corrected spin structure function g 1 (x, Q 2 ). These splitting functions, which are presented in the MS scheme, are derived from the order α 2 s contribution to the anomalous dimensions γ m ij (i, j = q, g). The latter correspond to the local operators which appear in the operator product expansion of two electromagnetic currents. Some of the properties of the anomalous dimensions will be discussed. In particular we find that in order α 2 s the supersymmetric relation γ m qq + γ m gq − γ m qg − γ m gg = 0 is violated.

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