Neutrino mass patterns, R-parity violating supersymmetry and associated phenomenology

Motivated by the recent SuperKamiokande results on atmospheric neutrinos, we incorporate massive neutrinos, with large angle oscillation between the second and third generations, in a theory with R-parity violating supersymmetry. The general features of such a theory are briefly reviewed. We emphasize its testability through the observation of comparable numbers of muons and taus, produced together with the W-boson, in decays of the lightest neutralino. A distinctly measurable decay gap is another remarkable feature of such a scenario.Comment: 7 pages, latex, talk delivered at the Discussion Meeting on Neutrino Physics, Physical Research Laboratory, Ahmedabad, India, February 2-4, 199

High-scale validity of a two Higgs doublet scenario: metastability included

We make an attempt to identify regions in a Type II Two-Higgs Doublet Model, which correspond to a metastable electroweak vacuum with lifetime larger than the age of the universe. We analyse scenarios which retain perturbative unitarity up to Grand unification and Planck scales. Each point in the parameter space is restricted using Data from the Large Hadron Collider (LHC) as well as flavor and precision electroweak constraints. We find that substantial regions of the parameter space are thus identified as corresponding to metastability, which compliment the allowed regions for absolute stability, for top quark mass at the high as well as low end of its currently allowed range. Thus, a two-Higgs doublet scenario with the electroweak vacuum, either stable or metastable, can sail through all the way up to the Planck scale without facing any contradictions

Some Signals for a Light Neutralino

If a light gaugino sector exists in the supersymmetric standard model then the mass of lightest neutralino may be of the order of 1 GeV or less. As a consequence of neutral flavor violation in supersymmetric theories $B_s$-meson may decay into a pair of lightest neutralinos in such a case. It is found that the parameter space for such light neutralinos can be appreciably constrained by looking for such decays. We also show how a rare B-decays ($B \longrightarrow K(K^{*}) + invisible$ channels) can help us in probing a light neutralino in B-factories in a reasonably model- independent manner. Finally, we observe that that the decay of a tau-lepton into a muon and a pair of light neutralinos can cause a violation of weak universality which is larger in magnitude than that from any source known so far.Comment: LaTex File, 6 Pages, Two Figures (available from authors by request). Presented at the International Workshops on Particle Theory and Phenomenology, IITAP, Iowa State University, USA, May 17-26, 199

Scalar three-body decays and signals for new physics

If massive invisible particles are pair-produced in a three-body decay, then the energy distribution of the other (visible) product is sensitive to the mass of the invisible pair. We use this fact in the context of a Higgs boson decaying into (i)a Z-boson and two massive neutrinos of a fourth generation, and (ii)a Z and two lightest particles in the minimal supersymmetric standard model. We discuss how the Z-energy spectrum in each case can reflect the values of the parameters in such models. (3 figures, hard copies available from authers on request).Comment: 11 pages, latex, MRI-PHY/8/9

Signals of supersymmetry with inaccessible first two families at the Large Hadron Collider

We investigate the signals of supersymmetry (SUSY) in a scenario where only the third family squarks and sleptons can be produced at the Large Hadron Collider (LHC), in addition to the gluino, charginos and neutralinos. The final states in such cases are marked by a multiplicity of top and/or bottom quarks. We study in particular, the case when the stop, sbottom and gluino masses are near the TeV scale due to which, the final state t's and b's are very energetic. We point out the difficulty in b-tagging and identifying energetic tops and suggest several event selection criteria which allow the signals to remain significantly above the standard model background. We show that such scenarios with gluino mass up to 2 TeV can be successfully probed at the LHC. Information on $\tan \beta$ can also be obtained by looking at associated Higgs production in the cascades of accompanying neutralinos. We also show that a combined analysis of event rates in the different channels and the effective mass distribution allows one to differentiate this scenario from the one where all three sfermion families are accessible.Comment: v3: 17 pages, 8 figures, 7 table