The Chirality-Flow Formalism in Charged Current Weak Interactions

Sammanfattning

The chirality-flow formalism is an extension of the spinor-helicity formalism in which scattering amplitudes are represented as diagrams of oriented flow lines between external spinors, which allows spinor bracket products to be read off easily. While the formalism has been explored and implemented for QED and QCD interactions, its application has not been explored systematically in the full electroweak sector. This thesis investigates the application of the chirality-flow formalism to charged current weak interactions. Since the the W boson is fundamentally chiral, only coupling to left-handed fermions, it proves to yield simplifications beyond those present in QED and QCD. We show that the amount of diagrams produced reduces by one fourth compared to equivalent interactions, imposing a "lock" on the chiral flow. Furthermore, the treatment of external W bosons demonstrates how the choice of reference vector eliminates one of the transverse polarization vectors. Finally, it is shown how the lock on chirality-flow propagates through massless fermion lines, constraining subsequent vertices of other interaction types.