Finding the Leptonic WWWW Decay Mode of a Heavy Higgs Boson

We reanalyze the extraction of the heavy Higgs boson signal $H\rightarrow W^+W^-\rightarrow \bar\ell\nu,\ell\bar\nu$ $(\ell=e\hbox{ or }\mu)$ from the Standard Model background at hadron supercolliders, taking into account revised estimates of the top quark background. With new acceptance criteria the detection of the signal remains viable. Requiring a forward jet-tag, a central jet-veto, and a large relative transverse momentum of the two charged leptons yields $S/\sqrt B>6$ for one year of running at the SSC or LHC.Comment: LaTex(Revtex), 9 pages, 6 figures (available upon request), MAD/PH/75

Supersymmetry Phenomenology at Hadron Colliders

The phenomenology of a low-energy supersymmetry at hadron colliders is discussed with consideration of the minimal supergravity model, with a large top quark Yukawa coupling at the grand unification mass scale, and gauge mediated symmetry breaking models. Possible supersymmetry interpretations of some unexplained events are mentioned.Comment: 11 pages, Latex2.09, uses sprocl.sty (included) and epsf.sty. 5 postscript figures. Talk presented at COSMO 97: International Workshop on Particle Physics and the Early Universe, Lancaster, UK, Sept. 1997. Postscript file of complete paper also available at http://pheno.physics.wisc.edu/pub/preprints/1998/madph-98-1034.ps.Z or at ftp://pheno.physics.wisc.edu/pub/preprints/1998/madph-98-1034.ps.

Supersymmetry vis-a-vis Muon Colliders

The potential of muon colliders to study a low-energy supersymmetry is addressed in the framework of the minimal supergravity model, whose predictions are first briefly surveyed. Foremost among the unique features of a muon collider is s-channel production of Higgs bosons, by which Higgs boson masses, widths, and couplings can be precisely measured to test the predictions of supersymmetry. Measurements of the threshold region cross sections of W^+ W^-, t t-bar, Zh, chargino pairs, slepton and sneutrino pairs will precisely determine the corresponding masses and test supersymmetric radiative corrections. At the high-energy frontier a 3 to 4 TeV muon collider is ideally suited to study heavy scalar supersymmetric particles.Comment: 14 pages, Latex2.09, uses aipproc.sty and espf.sty. 10 postscript figures. Invited talk presented at the Workshop on Physics at the First Muon Collider and at the Front End of a Muon Collider, Fermilab, November 1997. Postscript file of complete paper also available from the UW-Madison Phenomenology preprint archives at ftp://pheno.physics.wisc.edu/pub/preprints/1998/madph-98-1038.ps.Z o

Higgs Physics and Supersymmetry

The quest for the physics underlying the breaking of the electroweak symmetry and the generation of mass is surveyed.Comment: 14 pages, Latex2.09, uses sprocl.sty and epsf.sty, 13 postscript files included. Talk presented at the Richard Arnowitt Fest: A Symposium on Supersymmetry and Gravitation, College Station, Texas, April 1998. Local-no: MADPH-98-106

Neutrino Masses and Mixing at the Millennium

Recent evidence for neutrino oscillations has revolutionized the study of neutrino masses and mixing. This report gives an overview of what we are learning from the neutrino oscillation experiments, the prospects for the near term, and the bright future of neutrino mass studies.Comment: References added. Latex2.09, uses epsf.sty and aipproc.sty, 16 pages, 14 figures. Talk presented at the 5th International Conference on Physics Potential and Development of mu^+ mu^- Colliders, San Francisco, December 199

Lepton Flavor Violating Era of Neutrino Physics

The physics agenda for future long-baseline neutrino oscillation experiments is outlined and the prospects for accomplishing those goals at future neutrino facilities are considered. Neutrino factories can deliver better reach in the mixing and mass-squared parameters but conventional super-beams with large water or liquid argon detectors can probe regions of the parameter space that could prove to be interesting.Comment: 12 pages, Latex, uses sprocl.sty and epsf.sty. 5 postscript figures. Talk presented at Joint U.S./Japan Workshop On New Initiatives In Lepton Flavor Violation and Neutrino Oscillation With High Intense Muon and Neutrino Sources, Honolulu, Hawaii, October 200

Overview of Physics at a Muon Collider

Muon colliders offer special opportunities to discover and study new physics. With the high intensity source of muons at the front end, orders of magnitude improvements would be realized in searches for rare muon processes, in deep inelastic muon and neutrino scattering experiments, and in long-baseline neutrino oscillation experiments. At a 100 to 500 GeV muon collider, neutral Higgs boson (or techni-particle) masses, widths and couplings could be precisely measured via s-channel production. Also, threshold cross-section studies of W+ W-, t t-bar, Zh and supersymmetric particle pairs would precisely determine the corrresponding masses and test supersymmetric radiative corrections. At the high energy frontier a 3 to 4 TeV muon collider is ideally suited for the study of scalar supersymmetric particles and extra Z-bosons or strong WW scattering.Comment: Latex2.09 using aipproc.sty (included) and epsf.sty. 15 pages, 11 postscript figures. Invited talk at the 4th International Conference on the Physics Potential and Development of mu+ mu- Colliders, San Francisco, December 199

Breaking Eight-fold Degeneracies in Neutrino CP Violation, Mixing, and Mass Hierarchy

We identify three independent two-fold parameter degeneracies (\delta, \theta_{13}), sgn(\delta m^2_{31}) and (\theta_{23}, \pi/2-\theta_{23}) inherent in the usual three-neutrino analysis of long-baseline neutrino experiments, which can lead to as much as an eight-fold degeneracy in the determination of the oscillation parameters. We discuss the implications these degeneracies have for detecting CP violation and present criteria for breaking them. A superbeam facility with a baseline at least as long as the distance between Fermilab and Homestake (1290 km) and a narrow band beam with energy tuned so that the measurements are performed at the first oscillation peak can resolve all the ambiguities other than the (\theta_{23}, \pi/2-\theta_{23}) ambiguity (which can be resolved at a neutrino factory) and a residual (\delta, \pi-\delta) ambiguity. However, whether or not CP violation occurs in the neutrino sector can be ascertained independently of the latter two ambiguities. The (\delta,\pi-\delta) ambiguity can be eliminated by performing a second measurement to which only the \cos\delta terms contribute. The hierarchy of mass eigenstates can be determined at other oscillation peaks only in the most optimistic conditions, making it necessary to use the first oscillation maximum. We show that the degeneracies may severely compromise the ability of the proposed SuperJHF-HyperKamiokande experiment to establish CP violation. In our calculations we use approximate analytic expressions for oscillation probabilitites that agree with numerical solutions with a realistic Earth density profile.Comment: Revtex (singlespaced), 35 pages, 15 postscript figures, uses psfig.st