Precise Numerical Evaluation of the Scalar One-Loop Integrals with the Infrared Divergence

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We present a new approach for obtaining very precise integration results for infrared vertex and box diagrams, where the integration is carried out directly without performing any analytic integration of Feynman parameters. Using an appropriate numerical integration routine with an extrapolation method, together with a multi-precision library, we have obtained integration results which agree with the analytic results to 10 digits even for such a very small photon mass as 10⁻¹⁵⁰ GeV in the infrared vertex diagram.