Consider the $s$-channel mediated top quark production process $$ d + \overline d \rightarrow t + \overline t$$ Using the Feynman rules for QCD, the amplitude contains a color factor $$[c^\dagger ...
I am reading a book on perturbative QCD by John Collins. In Chapter 5, the terms reduced graph and pinch-singular surface are used for the analysis of mass singularities. However, their meanings are ...
In analogy to QED, the following Feynman diagram is a diagram contributing to the vacuum polarization effect, leading to anti-screening, asymptotic freedom and running of the strong coupling constant. ...
Whenever Feynman rules are stated they are always without any mention of the helicities - this I find to be very confusing. How does one introduce and account for that? Is there an intuitive/simple ...