paper

Gauge independent transverse and longitudinal self-energies and vertices via the pinch technique

arXiv:hep-ph/9406258 · doi:10.1103/PhysRevD.50.5958

Abstract

In the context of the Standard Model we show how to apply the pinch technique to four-fermion amplitudes with non-conserved external charged currents,in order to construct to one-loop order gauge independent self-energies and vertices. We discuss the technical difficulties arising due to the presence of longitudinal contributions from the W and Goldstone boson () propagators, and derive gauge independent , , and effective self-energies, and vertices. The quantities so constructed satisfy a set of Ward identities, whose validity enforces the gauge invariance of the physical amplitude considered; their derivation does not require knowledge of the explicit closed form of the gauge independent self-energies and vertices. Use of these Ward identities enables the decomposition of the amplitude in manifestly gauge independent transverse and longitudinal structures with distinct kinematic properties. Explicit one-loop calculations are carried out, and several applications of the results are briefly discussed.}

29 pages, NYU--TH--94/05/02

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