FEYN CALC SYMBOL

OneLoop


calculates the one-loop Feynman diagram amplitude (n-point, where n4 and the highest tensor rank of the integration momenta (after cancellation of scalar products) may be up to 3; unless OneLoopSimplify is used). The argument q denotes the integration variable, i.e., the loop momentum. OneLoop[name, q, amplitude] has as first argument a name of the amplitude. If the second argument has head FeynAmp then OneLoop[q, FeynAmp[name, k, expr]] and OneLoop[FeynAmp[name, k, expr]] tranform to OneLoop[name, k, expr]. NOTICE: While OneLoop is restricted to 't Hooft Feynman gauge, the function OneLoopSimplify does not have this restriction (but is usually slower). WARNING: If you encounter anomalies: The default setting of West is True, i.e., the way  tr(gamma^mugamma^nugamma^rhogamma^sigmagamma^taugamma^lambdagamma^5) is calculated in D dimensions has changed compared to the old FeynCalc version. Please keep in mind that the issue of gamma^5schemes is inherintly tricky.

ExamplesExamplesopen allclose all

Basic Examples  (1)Basic Examples  (1)

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Remember that FAD[{q,mf},{q-k,mf}] is a fast possibility to enter 1/( (q^2-mf^2) ( (q-k)^2-mf^2) ).
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The input to OneLoop may be in 4 dimensions, since the function changes the dimension of the objects automatically to the setting of the Dimension option (D by default).
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