The Bloch Nordsieck (BN) restoration for ll ̅ → qq ̅

Abstract

Usually, the Bloch-Nordsieck theorem is expected to be violated in weak interactions, as the corresponding asymptotic states are not weak singlets. However, a manifest gauge-invariant approach replaces the asymptotic states with composite states, and thereby restores the Bloch-Nordsieck theorem. The Fröhlich-Morchio-Strocchi mechanism ensures that this is in agreement with existing phenomenology. We outline the necessary steps of this construction.

Vector boson scattering from the lattice

“…But this also implies that higher orders in v will lead to deviations from the results of ordinary perturbation theory. Indeed, such deviations have previously been observed on [18] and off [9,13,15,16,32] the lattice. In addition, because the FMS mechanism is still perturbative in nature, it is not able to describe genuine nonperturbative surplus bound states, e.g.…”

“…This therefore both reproduces the success of perturbation theory and validates its use in this kinematical region. Only towards the TeV range first indications appear that again deviations due to the FMS-subdominant constituents could play a role [9,15,16,32].…”

Amplitude Factorization in the Electroweak Standard Model

“…[23,24]. Our analysis is also in shape to include the effects of mixing, decays and the projection onto observed states as outlined in [25], which can lead to possible mis-cancellations of logarithmically enhanced contributions [26] or to mechanisms restoring the cancellation [27]. We focus in particular on the underlying kinematic region in which factorization, including different mass shells and possibly recoils, take place, and on the structure of the evolving amplitude as a vector in the space of color, isospin, and chirality structures.…”