Non-conserved currents and gauge-restoring schemes in single W production

TL;DR

This paper extends the treatment of fermionic loop corrections to include massive external fermions and non-conserved weak currents, analyzing gauge invariance and finite-width effects in single W production at high-energy colliders.

Contribution

It introduces a generalized scheme for including imaginary parts of fermionic loops with massive fermions and non-conserved currents, comparing gauge-invariant methods in W production.

Findings

No significant differences between fermion loop scheme and other gauge-preserving methods.

Numerical comparisons at LEP2 and LC energies show consistent results.

Finite-width effects are effectively handled in the generalized scheme.

Abstract

We generalize the inclusion of the imaginary parts of the fermionic one-loop corrections for processes with unstable vector bosons to the case of massive external fermions and non conservation of weak currents. We study the effect of initial and final state fermion masses in single W production in connection with the gauge-invariant treatment of the finite-width effects of W and Z bosons, giving numerical comparisons of different gauge-invariance-preserving schemes in the energy range of LEP2 and LC for e+e- -> e- v u d. We do not find significant differences between the results obtained in the imaginary part fermion loop scheme and in other exactly gauge preserving methods.