Expansion by regions meets angular integrals

• Published in: The journal of high energy physics Vol. 2024; no. 8; pp. 138 - 24
• Main Authors: Smirnov, Vladimir A., Wunder, Fabian
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 20-08-2024; Springer Nature B.V; SpringerOpen
• Subjects: Asymptotic methods; Asymptotic properties; Asymptotic series; Classical and Quantum Gravitation; Effective Field Theories of QCD; Elementary Particles; Higher-Order Perturbative Calculations; Integrals; Physics; Physics and Astronomy; Quantum Field Theories; Quantum Field Theory; Quantum Physics; Quantum theory; Regular Article - Theoretical Physics; Relativity Theory; Representations; String Theory; Effective Field Theories of QCD; Higher-Order Perturbative Calculations
• ISSN: 1029-8479; 1029-8479
• DOI: 10.1007/JHEP08(2024)138

A
bstract
We study the small-mass asymptotic behavior of so-called angular integrals, appearing in phase-space calculations in perturbative quantum field theory. For this purpose we utilize the strategy of expansion by regions, which is a universal method both for multiloop Feynman integrals and various parametric integrals. To apply the technique to angular integrals, we convert them into suitable parametric integral representations, which are accessible to existing automation tools. We use the code asy.m to reveal regions contributing to the asymptotic expansion of angular integrals. To evaluate the contributions of these regions in an epsilon expansion we apply the method of Mellin-Barnes representation. Our approach is checked against existing results on angular integrals revealing a connection between contributing regions and angular integrals constructed from an algebraic decomposition. We explicitly calculate the previously unknown asymptotics for angular integrals with three and four denominators and formulate a conjecture for the leading asymptotics and the pole part for a general number of denominators and masses.