Hi everyone. I was trying to reproduce the calculation needed to include the QCD correction to the low energy electroweak Lagrangian. In particular I am looking at Peskin section 18.2. In equation 18.35 an extra minus sign appears on the numerator of the second fermion propagator.(adsbygoogle = window.adsbygoogle || []).push({});

Can anyone explain me why?

Thanks

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# Doubt on sign of the propagator on Peskin

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