Reduction of one-loop n-point integrals

TL;DR

This paper introduces new analytical expressions for three and four-point one-loop integrals in the small Gram determinant region and proposes a reduction method for n-point integrals with n≥5 to improve computational efficiency.

Contribution

It provides explicit formulas for three and four-point integrals and a novel reduction technique for n≥5 point integrals, enhancing numerical stability and efficiency.

Findings

Explicit expressions for three and four-point integrals in small Gram determinant region

Reduction of n≥5 point integrals to five (n-1)-point integrals

Improved CPU time and reduced numerical errors in computations

Abstract

In this paper, we focus on both analytical expressions of three and four point integrals for the case of small Gram determinant and numerical improvement of $n$-point integrals for $n\ge5$. Explicit expressions of three and four-point integrals in the small Gram determinant region are provided by the new method. Furthermore, $n$-point one-loop integral with $n\ge5$ is always reduced to five number of $(n-1)$-point integrals regardless of how many points are on a loop, which improves dramatically the CPU time consuming. Besides, the theoretical and numerical error riginating from computing higher dimensional Cayley matrix could be reduced by the dimension of the matrix being always fixed to five. We suggest a general reduction formulae for five and more point scalar, vector, and tensor integrals at one-loop level.