Naturalness and Electro-weak Symmetry Breaking

TL;DR

This paper reviews the principle of naturalness in quantum field theories, focusing on the stability of the Higgs boson mass and exploring various solutions like compositeness, supersymmetry, and extra-dimensional models.

Contribution

It provides a comprehensive review of naturalness problems in electroweak symmetry breaking and discusses recent alternative mechanisms beyond traditional solutions.

Findings

Standard Model Higgs mass is unstable against radiative corrections.

Supersymmetry and compositeness are canonical solutions to naturalness issues.

New models like little Higgs and gauge-Higgs unification are under investigation.

Abstract

The Principle of Naturalness of small parameters of a theory is reviewed. While quantum field theories constructed from gauge fields and fermions only are natural, those containing elementary scalar fields are not. In particular the Higgs boson mass in the Standard Model of electro-weak forces is not stable against radiative corrections. Two old canonical solutions of this problem are: (i) where the Higgs boson is a fermion-antifermion composite (technicolour solution) or otherwise (ii) we need supersymmetry to protect the mass of elementary Higgs boson from possible large radiative corrections. In recent years some other mechanisms for electroweak symmetry breaking have been under intense investigation. These include the little Higgs models and the gauge-Higgs unification models where the Higgs boson is the zero mode of the extra-dimensional component of a higher dimensional gauge field. Naturalness issues of such models are also briefly reviewed.