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Singlet and nonsinglet three-loop massive form factors

M. Fael, F. Lange, K. Schönwald, M. Steinhauser

Physical Review D, 2022

51 citations

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. ar X iv :2 20 7. 00 02 7v 1 [ he pph ] 3 0 Ju n 20 22

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