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arXiv · 2207.00027

Singlet and non-singlet three-loop massive form factors

Matteo Fael·Fabian Lange·Kay Schönwald·Matthias Steinhauser
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Abstract

We consider Quantum Chromodynamics with external vector, axial-vector, scalar and pseudo-scalar currents and compute three-loop corrections to the corresponding vertex function taking into account massive quarks. We consider all non-singlet contributions as well as those singlet contributions where the external current couples to a massive quark loop. We apply a semi-numerical method which is based on expansions around singular and regular kinematical points. They are matched at intermediate values of the squared partonic center-of-mass energy $s$ which allows to cover the whole kinematic range for negative and positive values of $s$. Our method permits a systematic increase of the precision by varying the expansion depth and the choice of the intermediate matching points. In our current set-up we have at least seven significant digits for the finite contribution of all form factors. We present our results as a combination of series expansions and interpolation functions which allows for a straightforward use in practical applications.

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Matteo Fael, Fabian Lange, Kay Schönwald, Matthias Steinhauser. 2022-06-30. Singlet and non-singlet three-loop massive form factors. https://doi.org/10.1103/physrevd.106.034029

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