The NMSSM Close to the R-symmetry Limit and Naturalness in h→aah \to aa Decays for m_a<2\mb

Dominant decay of a SM-like Higgs boson into particles beyond those contained in the minimal supersymmetric standard model has been identified as a natural scenario to avoid fine tuning in electroweak symmetry breaking while satisfying all LEP limits. In the simplest such extension, the next-to-minimal supersymmetric model, the lightest CP-even Higgs boson can decay into two pseudoscalars. In the scenario with least fine tuning the lightest CP-even Higgs boson has mass of order 100 GeV. In order to escape LEP limits it must decay to a pair of the lightest CP-odd Higgs bosons with Br(h -> aa)>.7 and m_a \tau^+ \tau^- or light quarks and gluons). The mass of the lightest CP-odd Higgs boson is controlled by the soft-trilinear couplings, A_\lambda(m_Z) and A_\kappa(m_Z). We identify the region of parameter space where this situation occurs and discuss how natural this scenario is. It turns out that in order to achieve m_a < 2 m_b with A_\lambda(m_Z), A_\kappa(m_Z) of order the typical radiative corrections, the required tuning of trilinear couplings need not be larger than 5-10 %. Further, the necessity for this tuning can be eliminated in specific SUSY breaking scenarios. Quite interestingly, Br(h -> aa) is typically above 70 % in this region of parameter space and thus an appropriately large value requires no additional tuning.Comment: 33 pages, 25 figure

Detecting and Studying Higgs Bosons

I review the ability of the LHC (large hadron collider), NLC (next linear lepton collider) and FMC (first muon collider) to detect and study Higgs bosons, with emphasis on the Higgs bosons of extended Higgs sectors, especially those of the minimal supersymmetric standard model (MSSM). Particular attention is given to means for distinguishing the lightest neutral CP-even Higgs boson of the MSSM from the single Higgs boson of the minimal Standard Model (SM).Comment: 65 pages, to appear in ``Perspectives on Higgs Physics'', ed. G. Kane, 2nd edition (World Scientific Publishing). Full postscript file is available via anonymous ftp at ftp://ucdhep.ucdavis.edu/gunion/perspectives97.p

A Simplified Summary of Supersymmetry

I give an overview of the motivations for and theory/phenomenology of supersymmetry.Comment: 24 pages, to appear in ``Future High Energy Colliders'', proceedings of the ITP Symposium, U.C. Santa Barbara, October 21-25, 1996, AIP Press. Also presented at the Aspen Winter Conference on High Energy Physics, January 1997, Aspen, CO. Full postscript file, is available via anonymous ftp at ftp://ucdhep.ucdavis.edu/gunion/itp96.p

Guaranteed Detection of a Minimal Supersymmetric Model Higgs Boson at Hadron Supercolliders

We demonstrate that expected efficiencies and purities for $b$-tagging at SSC/LHC detectors should allow detection of at least one of the Higgs bosons of the Minimal Supersymmetric Model in t\anti t~Higgs production, with Higgs\rta b\anti b decay, over a substantial range of supersymmetric parameter space. In particular, with the addition of this mode to those previously considered, there is no region of supersymmetric parameter space for which {\it none} of the Higgs bosons of the model can be seen at the SSC/LHC.Comment: 9 pages, uses phyzzx.tex and tables.tex macros, full postscript file, including embedded figures, available via anonymous ftp at ucdhep.ucdavis.edu as [anonymous.gunion]hbb_susy.ps, preprint UCD-93-2

Detecting and Studying e+e−→H0A0,H+H−e^+e^-\to H^0A^0,H^+H^- in the MSSM: Implications of Supersymmetric Decays and Discriminating GUT Scenarios

We demonstrate that supersymmetric decays, as typified by the predictions of several GUT-scale boundary condition choices, do not prevent detection of $Z^* \to H^0A^0,H^+H^-$, at a $1-4$ TeV $e^+e^-$ or $\mu^+\mu^-$ collider operating at anticipated luminosity. For much of parameter space the relative branching ratios for various SUSY and non-SUSY decays can be measured with sufficient accuracy that different GUT-scale boundary condition choices can be distinguished from one another at a very high confidence level.Comment: 54 pages, full postscript file also available via anonymous ftp at ftp://ucdhep.ucdavis.edu/gunion/pair.p

Extra Dimension Kaluza-Klein Excitations and Electroweak Symmetry Breaking

We review the possibilities that the Kaluza-Klein excitations of graviton states induce electroweak symmetry breaking and that electroweak symmetry breaking could have a large impact on KK phenomenology.Comment: 6 pages, no figure