Electroweak symmetry breaking and large extra dimensions

If spacetime contains large compact extra dimensions, the fundamental mass scale of nature, ii, may be close to the weak scale, allowing gravitational physics to significantly modify electroweak symmetry breaking. Operators of the form (1/Lambda(2))\phi(dagger)D(mu)phi\(2) and (1/Lambda(2))phi(dagger)W(mu nu)B(mu nu)phi, where W-mu nu and B-mu nu 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 less than or similar to Lambda less than or similar to 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) x U(1) symmetry beneath Lambda. If there is a Higgs doublet, then operators of the form (1/Lambda(2))phi(dagger)phi(G(2),F-2), where G(mu nu) and F-mu nu 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 yy, respectively. At Run II of the Tevatron collider, a yy 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. (C) 1999 Published by Elsevier Science B.V. All rights reserved.