Anomalous Sudakov Form Factors

TL;DR

This paper reveals that in certain broken gauge theories, resummation of radiative corrections can lead to amplitudes that grow with energy, contrary to the usual suppression, especially in models with large mass splittings.

Contribution

It demonstrates that in broken gauge theories, resummation can produce positive exponentials, causing amplitudes to grow with energy, a novel insight into high-energy behavior.

Findings

Resummation can lead to amplitude growth in broken gauge theories.

Magnetic dipole moments dominate Z' decay at high energies.

High-energy amplitudes can violate traditional suppression expectations.

Abstract

While radiative corrections of infrared origin normally depress high energy amplitudes (Sudakov form factors), we find that in some cases resummation of leading effects produces exponentials with positive exponents, giving rise to amplitudes that grow indefinitely with energy. The effect happens in broken gauge theories like the electroweak sector of the Standard Model, and is related to the existence of amplitudes that do not respect the gauge symmetry, and that contrary to expectations do not vanish in the very high energy limit, but rather become dominant. As a working example we consider a model with two chiral abelian gauge groups $U'(1)\otimes U(1)$ with large mass splitting $M_{Z'} \gg M_{Z} $, and we compute leading radiative corrections corrections to the decay of the heavy extra ${Z'}$ boson into light fermions. For proper fermionic charges, the chirality breaking magnetic dipole moment, although mass suppressed, becomes the dominant contribution to the $Z'$ width at very high energies.