UNITARITY CONSTRAINTS ON GRAND UNIFIED MODELS

Dec, 1988
51 pages
Published in:
  • Phys.Rev.D 40 (1989) 207
Report number:
  • MAD/TH/88-20

Citations per year

196919801991200220120246810
Abstract: (APS)
We present a simplified method for the calculation of low-energy unitarity constraints on grand unified broken-supersymmetric models based on the Goldstone-boson equivalence theorem for high-energy scattering in gauge theories, the fermion-boson equivalence theorem for supersymmetric theories, and the evolution of couplings under the renormalization group. We apply the method to the "flipped" SU(5)×U(1) superstring model, obtain high-energy unitarity constraints at the grand unified scale MG=4×1016 GeV, and then use the renormalization-group equations to evolve the constraints to the low-energy mass scale MW. We investigate the peculiarities of the renormalization-group flow and the existence of critical surfaces at which the scalar superpotential couplings diverge at MG. We find upper bounds on the superpotential couplings at low energies and use these to establish absolute upper bounds on the top-quark mass, mt≲200 GeV, and on the lightest neutral-Higgs-boson mass, MH10≲155 GeV in the SU(5)×U(1) model. We also obtain an upper bound on MH10 as a function of mt which shows that MH10≲125 GeV for favored values of the ratios of Higgs vacuum expectation values.
  • GRAND UNIFIED THEORY: SU(5) X U(1)
  • UNITARITY: CONSTRAINT
  • SUPERSYMMETRY
  • MODEL: STRING
  • RENORMALIZATION GROUP
  • COUPLING CONSTANT
  • MASS SPECTRUM
  • MASS: TOP
  • TOP: MASS
  • HIGGS PARTICLE: MASS