Electroweak Symmetry Breaking and Large Extra Dimensions

TL;DR

This paper explores how large extra dimensions could lower the fundamental scale of gravity, affecting electroweak symmetry breaking, Higgs boson properties, and collider signals, with potential discoveries at Tevatron and LHC.

Contribution

It introduces new operators from extra dimensions that modify electroweak and Higgs physics, relaxing bounds and predicting collider signatures.

Findings

Operators remove electroweak bounds on Higgs mass for Lambda between 4-11 TeV.

Higgs production and decay are altered by extra-dimensional operators.

Collider signals at Tevatron and LHC could reveal extra dimensions if Lambda is within specific ranges.

Abstract

If spacetime contains large compact extra dimensions, the fundamental mass scale of nature, $Lambda$, may be close to the weak scale, allowing gravitational physics to significantly modify electroweak symmetry breaking. Operators of the form $(1/Lambda^2) |phi^* D phi|^2$ and $(1/Lambda^2) phi^* W B phi$, where $W$ and $B$ are the SU(2) and U(1) field strengths and $phi$ is the Higgs field, remove the precision electroweak bound on the Higgs boson mass for values of $Lambda$ in a wide range: $4 TeV < Lambda < 11 TeV$. Within this framework, there is no preference between a light Higgs boson, a heavy Higgs boson, or a non-linearly realized SU(2)xU(1) symmetry beneath $Lambda$. If there is a Higgs doublet, then operators of the form $(1/Lambda^2) phi^* phi (G^2, F^2)$, where $G$ and $F$ are the QCD and electromagnetic field strengths, modify the production of the Higgs boson by gluon-gluon fusion, and the decay of the Higgs boson to 2 photons, respectively. At Run II of the Tevatron collider, a 2-photon signal for extra dimensions will be discovered if $Lambda$ is below 2.5 (1) TeV for a Higgs boson of mass 100 (300) GeV. Furthermore, such a signal would point to gravitational physics, rather than to new conventional gauge theories at $Lambda$. The discovery potential of the LHC depends sensitively on whether the gravitational amplitudes interfere constructively or destructively with the standard model amplitudes, and ranges from $Lambda$ = 3 - 10 (2 - 4) TeV for a light (heavy) Higgs boson.