288 research outputs found
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 -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 ( 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
Same-sign trileptons as a signal of sneutrino lightest supersymmetric partlcle
Contrary to common expectation, a left-sneutrinos can occasionally be the
lightest supersymmet- ric particle. This has important implications in both
collider and dark matter studies. We show that same-sign tri-lepton (SS3L)
events at the Large Hadron Collider, with any lepton having opposite sign
vetoed, distinguish such scenarios, up to gluino masses exceeding 2 TeV. The
jets + M ET signal rate is somewhat suppressed in this case, thus enhancing the
scope of leptonic signals.Comment: Version published in Phys.Lett.
Higher dimensional operators and LHC Higgs data : the role of modified kinematics
The inclusion of higher-dimensional gauge invariant operators induces new
Lorentz structures in Higgs couplings with electroweak gauge boson pairs. This
in principle affects the kinematics of Higgs production and decay, thereby
modifying the efficiencies of the experimental cuts compared to what
simulations based on the standard model interactions yield. Taking some sample
cases, we perform a rigorous analysis of how the efficiencies differ for
various strengths of the additional operator vis-a-vis the standard model
interactions, scanning over the values of both of them. While the response to
cuts can be markedly different in some regions, we find that the sensitivity to
new operator structures is relatively limited, so long as we remain confined to
the 2-sigma regions around the best fit signal strengths measured at the Large
Hadron Collider. We also show modifications to certain kinematical
distributions including the new operators in the diphoton final state.Comment: 26 pages, 9 figures; v2: Some numerical factors corrected,
conclusions unchanged. Comments and references added. Version to be published
in Phys.Rev.
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