N3LO calculation of the B to Xs gamma photon spectrum including complete light-fermion corrections, two massive fermion loops, and large-Nc terms, with improved results in kinetic and MSR mass schemes.
Analytic and Algorithmic Aspects of Generalized Harmonic Sums and Polylogarithms
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abstract
In recent three--loop calculations of massive Feynman integrals within Quantum Chromodynamics (QCD) and, e.g., in recent combinatorial problems the so-called generalized harmonic sums (in short $S$-sums) arise. They are characterized by rational (or real) numerator weights also different from $\pm 1$. In this article we explore the algorithmic and analytic properties of these sums systematically. We work out the Mellin and inverse Mellin transform which connects the sums under consideration with the associated Poincar\'{e} iterated integrals, also called generalized harmonic polylogarithms. In this regard, we obtain explicit analytic continuations by means of asymptotic expansions of the $S$-sums which started to occur frequently in current QCD calculations. In addition, we derive algebraic and structural relations, like differentiation w.r.t. the external summation index and different multi-argument relations, for the compactification of $S$-sum expressions. Finally, we calculate algebraic relations for infinite $S$-sums, or equivalently for generalized harmonic polylogarithms evaluated at special values. The corresponding algorithms and relations are encoded in the computer algebra package {\tt HarmonicSums}.
years
2026 4verdicts
UNVERDICTED 4representative citing papers
The authors construct μ-extensions of iterated integrals and nested sums over multiple alphabets, showing that they map polynomially in μ into the original function space (except for square-root cases) while preserving Hopf algebra structure via the quasi-shuffle product.
HyperPrecision is a new Mathematica package that evaluates general Horn-type multivariate hypergeometric functions and their ε-expansions to high precision by reducing Pfaffian PDE systems to solvable ODEs.
A general numerical framework is described for high-precision evaluation and analytic continuation of multivariate hypergeometric functions via Pfaffian systems and the Frobenius method.
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