alpha_s^3 conversion relation betweeen MS-bar and Euclidean quark masses

Abstract

We report on the analytical calculation of NNNLO (of order alpha_s^3) conversion factor between the MS-bar quark mass and the one defined in the so-called Regularization Invariant scheme. The NNNLO contribution in the conversion factor turns out to be relatively large and comparable to the known NNLO term.Comment: 4 pages, Latex, uses espcrc2.sty. The paper is also available via anonymous ftp at ftp://ttpux2.physik.uni-karlsruhe.de/ttp99/ttp99-39/ or via www at http://www-ttp.physik.uni-karlsruhe.de/Preprints