An introduction to gauge theories Written by three of the worlds leading experts on particle physics and the standard model including an award winning former director general of CERN this book provides a completely up to date account of gauge theories. Starting from Feynmans path integrals Feynman rules are derived gauge fixing and Faddeev Popov ghosts are discussed and renormalization group equations are derived. Several important applications to quantum electrodynamics and quantum chromodynamics (QCD) are discussed including the one loop derivation of asymptotic freedom for QCD