9,212 research outputs found
Higgs Sector of the Minimal Left-Right Symmetric Model
We perform an exhaustive analysis of the most general Higgs sector of the
minimal left-right symmetric model (MLRM). We find that the CP properties of
the vacuum state are connected to the Higgs spectrum: if CP is broken
spontaneously, the MLRM does not approach the Standard Model in the limit of a
decoupling left-right symmetry breaking scale. Depending on the size of the CP
phases scenarios with extra non-decoupling flavor-violating doublet Higgses or
very light SU(2) triplet Higgses emerge, both of which are ruled out by
phenomenology. For zero CP phases the non-standard Higgses decouple only if a
very unnatural fine-tuning condition is fulfilled. We also discuss
generalizations to a non-minimal Higgs sector.Comment: brief discussion of non-minimal Higgs sectors added, journal versio
A Model of Quark and Lepton Masses I: The Neutrino Sector
If neutrinos have masses, why are they so tiny? Are these masses of the Dirac
type or of the Majorana type? We are already familiar with the mechanism of how
to obtain a tiny Majorana neutrino mass by the famous see-saw mechanism. The
question is: Can one build a model in which a tiny Dirac neutrino mass arises
in a more or less "natural" way? What would be the phenomenological
consequences of such a scenario, other than just merely reproducing the
neutrino mass patterns for the oscillation data? In this article, a systematic
and detailed analysis of a model is presented, with, as key components, the
introduction of a family symmetry as well as a new SU(2) symmetry for the
right-handed neutrinos. In particular, in addition to the calculations of light
neutrino Dirac masses, interesting phenomenological implications of the model
will be presented.Comment: 25 (single-spaced) pages, 11 figures, corrected some typos in Table
I, added acknowledgement
Minimal Supersymmetric Pati-Salam Theory: Determination of Physical Scales
We systematically study the minimal supersymmetric Pati-Salam theory, paying
special attention to the unification constraints. We find that the SU(4)_c
scale M_c and the Left-Right scale M_R lie in the range 10^{10} GeV < M_c <
10^{14} GeV, 10^{3} GeV < M_R <10^{10} GeV (with single-step breaking at
10^{10} GeV), giving a potentially accessible scale of parity breaking. The
theory includes the possibility of having doubly-charged supermultiplets at the
supersymmetry breaking scale; color octet states with mass of order M_R^2/M_c;
magnetic monopoles of intermediate mass that do not conflict with cosmology,
and a 'clean' (type I) form for the see-saw mechanism of neutrino mass.Comment: 5 page
Lepton Flavor Violation and the Tau Neutrino Mass
We point out that, in the left-right symmetric model of weak interaction, if
mass is in the keV to MeV range, there is a strong correlation
between rare decays such as and
the mass. In particular, we point out that a large range of
masses are forbidden by the cosmological constraints on
in combination with the present upper limits on these processes.Comment: UMDHEP 94-30, 14 pages, TeX file, (some new references added
Geometric CP Violation with Extra Dimensions
We discuss how CP symmetry can be broken geometrically through orbifold
projections in hidden extra dimensions in the context of D-brane models for
particle unifications. We present a few toy models to illustrate the idea and
suggest ways to incorporate this technique in the context of realistic models.Comment: 6 pages, one figure; references updated and a new model adde
Collider Signature of Bulk Neutrinos in Large Extra Dimensions
We consider the collider signature of right-handed neutrinos propagating in
(large) extra dimensions, and interacting with Standard Model fields
only through a Yukawa coupling to the left-handed neutrino and the Higgs boson.
These theories are attractive as they can explain the smallness of the neutrino
mass, as has already been shown. We show that if is bigger than two,
it can result in an enhancement in the production rate of the Higgs boson,
decaying either invisibly or to a anti- quark pair, associated with an
isolated high charged lepton and missing transverse energy at future
hadron colliders, such as the LHC. The enhancement is due to the large number
of Kaluza-Klein neutrinos produced in the final state. The observation of the
signal event would provide an opportunity to distinguish between the normal and
inverted neutrino mass hierarchies, and to determine the absolute scale of
neutrino masses by measuring the asymmetry of the observed event numbers in the
electron and muon channels.Comment: 31 pages, 13 figures. v2: Added discussion on PDF uncertainties,
added reference
Effects of Decays of Tau Neutrinos Near A Supernova
We revisit the constraints implied by SN 1987 A observations on the decay
rate of a multi-MeV decaying into the visible channel , if its lifetime is more than 10 {\it sec.}. We
discuss its implication for the minimal left-right symmetric model with see-saw
mechanism for neutrino masses. We also speculate on the possible formation of a
``giant Capacitor" in intergalactic space due to the decay of "neutronization"
's and spin allignment possibility in the supernova.Comment: 29 Pages, Tex file, UMDHEP 94-4
The Left-Right SU(3)(L)xSU(3)(R)xU(1)(X) Model with Light, keV and Heavy Neutrinos
We construct a full left-right model for the electroweak interactions based
on the gauge symmetry. The fermion
content of the model is such that anomaly cancellation restricts the number of
families to be a multiple of three. One of the most important features of the
model is the joint presence of three light active neutrinos, three additional
neutrinos at keV mass scale, and six heavy ones with masses
around\textbf{} GeV. They form a well-motivated part of the spectrum
in the sense they address challenging problems related to neutrino oscillation,
warm dark matter, and baryogenesis through leptogenesis.Comment: 11 pages. Small corrections and typos fixed. Accepted for publication
in PR
Production of qqQQ final states in ee collisions in the left-right symmetric model
We consider the reaction ee ->qqQQ as a test of lepton number
non-conservation in the framework of the left-right-symmetric electroweak
model. The main contributions to this process are due to Majorana neutrino
exchange in t-channel and doubly charged Higgs (Delta{--}) exchange in
s-channel with a pair of right-handed weak bosons (WR) as intermediate state.
We show that in a linear ee collider with the collision energy of 1 TeV (1.5
TeV) the cross section of this process is 0.01 fb (1 fb), and it will, for the
anticipated luminosity of 10**{35} cm**{-2}, be detectable below the WR
threshold. We study the sensitivity of the reaction on the masses of the heavy
neutrino, WR and Delta{--}.Comment: 24 pages, 9 eps figures, uses axodraw.st
decays in the Left-Right Symmetric Model
We consider decays in the Left-Right Symmetric Model. Values
of observables sensitive to chiral structure such as the polarization
in the decays and the mixing-induced CP
asymmetries in the decays can deviate in the LRSM
significantly from the SM values. The combined analysis of and
as well as can be used to determine the
model parameters.Comment: 16 pages with 7 figures, Version to be published in PR
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