An Application of Rubi: Series Expansion of the Quark Mass Renormalization Group Equation
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We highlight how Rule-based Integration (Rubi) is an enhanced method of symbolic integration which allows for the integration of many difficult integrals not accomplished by other computer algebra systems. Using Rubi, many integration techniques become tractable. Integrals are approached using step-wise simplification, hence distilling an integral (if the solution is unknown) into composite integrals which highlight yet undiscovered integration rules. The motivating example we use is the derivation of the updated series expansion of the quark mass renormalization group equation (RGE) to five-loop order. This series provides the relation between a light quark mass in the modified minimal subtraction (MS) scheme defined at some given scale, e.g. at the tau-lepton mass scale, and another chosen energy scale, s. This relation explicitly depicts the renormalization scheme dependence of the running quark mass on the scale parameter, s, and is important in accurately determining a light quark mass at a chosen scale. The five-loop QCD β(a_s) and γ(a_s) functions are used in this determination.
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