20 research outputs found
A Supersymmetric Composite Model of Quarks and Leptons
We present a class of supersymmetric models with complete generations of
composite quarks and leptons using recent non-perturbative results for the low
energy dynamics of supersymmetric QCD. In these models, the quarks arise as
composite "mesons" and the leptons emerge as composite "baryons." The quark and
lepton flavor symmetries are linked at the preon level. Baryon number violation
is automatically suppressed by accidental symmetries. We give some speculations
on how this model might be made realistic.Comment: 10 pages, LaTeX 2
Models for Geometric CP Violation with Extra Dimensions
In a recent paper, two of us (D.C. and R.N.M.) proposed a new way to break CP
symmetry geometrically using orbifold projections. The mechanism can be
realized in the five dimensional brane bulk picture. In this paper, we
elaborate on this proposal and provide additional examples of models of this
type. We also note the phenomenological implications of some of these models.Comment: 15 pages, latex; several typos corrected; a new reference adde
Radiative Transmission of Lepton Flavor Hierarchies
We discuss a one loop model for neutrino masses which leads to a seesaw-like
formula with the difference that the charged lepton masses replace the unknown
Dirac mass matrix present in the usual seesaw case. This is a considerable
reduction of parameters in the neutrino sector and predicts a strong
hierarchical pattern in the right handed neutrino mass matrix that is easily
derived from a family symmetry. The model is based on the left-right
gauge group with an additional discrete symmetry which gives vanishing
neutrino Dirac masses and finite Majorana masses arising at the one loop level.
Furthermore, it is one of the few models that naturally allow for large (but
not necessarily maximal) mixing angles in the lepton sector. A generalization
of the model to the quark sector requires three iso-spin singlet vector-like
down type quarks, as in . The model predicts an inert doublet type scalar
dark matter.Comment: 11 pages, 1 figur
TeV Scale Left Right Symmetry and Flavor Changing Neutral Higgs Effects
In minimal left-right symmetric models, the mass of the neutral Higgs field
mediating tree-level flavor changing effects (FCNH) is directly related to the
parity breaking scale. Specifically, the lower bound on the Higgs mass coming
from Higgs-induced tree-level effects, and exceeding about 15 TeV, would tend
to imply a W_R mass bound much higher than that required by gauge exchange loop
effects -- the latter allowing W_R masses as low as 2.5 TeV. Since a W_R mass
below 4 TeV is accessible at the LHC, it is important to investigate ways to
decouple the FCNH effects from the W_R mass. In this paper, we present a model
where this happens, providing new motivation for LHC searches for W_R in the 1
- 4 TeV mass range.Comment: 10 pages, 1 figure. v3: a typo and a bug in the constraint from
D0-D0bar mixing fixed. Plots slightly changed, results and conclusions
untouched. Matches journal versio
Simple supersymmetric solution to the strong CP problem
It is shown that the minimal supersymmetric left-right model can provide a
natural solution to the strong {\it CP} problem without the need for an axion,
nor any additional symmetries beyond supersymmetry and parity.Comment: Plain Latex. 10 pages, including two figures which are part of the
Latex file. Shortened version, to appear in Phys. Rev. Lett. 7
Economical Doublet-Triplet Splitting and Strong Suppression of Proton Decay in SO(10)
We present a new approach to realizing the Dimopoulos-Wiczek mechanism for
doublet-triplet splitting in supersymmetric SO(10). The method can be used to
achieve strong suppression of proton decay in a straightforward manner and is
relatively economical; in particular the particle spectrum required for its
implementation is consistent with the constraints from string compactification
at Kac-Moody level two. We construct two examples of realistic models based on
this idea. These models have no unwanted flat directions and do not make use of
any nonrenormalizable operators to stabilize the vacuum thereby maintaining
coupling constant unification as a prediction. The first model is characterised
by a simple discrete symmetry that guarantees naturalness at the renormalizable
level while also eliminating all potentially dangerous R-parity violating
effects. The second model predicts the strong suppression of Higgsino mediated
proton decay. In both models the light MSSM doublets emerge from two different
{\bf 10}'s so that there is considerable flexibility in constructing realistic
fermion masses and CKM angles.Comment: 6 pages Revtex; UMD-PP-99-01
Gauged Flavor Group with Left-Right Symmetry
We construct an anomaly-free extension of the left-right symmetric model,
where the maximal flavor group is gauged and anomaly cancellation is guaranteed
by adding new vectorlike fermion states. We address the question of the lowest
allowed flavor symmetry scale consistent with data. Because of the mechanism
recently pointed out by Grinstein et al. tree-level flavor changing neutral
currents turn out to play a very weak constraining role. The same occurs, in
our model, for electroweak precision observables. The main constraint turns out
to come from WR-mediated flavor changing neutral current box diagrams,
primarily K - Kbar mixing. In the case where discrete parity symmetry is
present at the TeV scale, this constraint implies lower bounds on the mass of
vectorlike fermions and flavor bosons of 5 and 10 TeV respectively. However,
these limits are weakened under the condition that only SU(2)_R x U(1)_{B-L} is
restored at the TeV scale, but not parity. For example, assuming the SU(2)
gauge couplings in the ratio gR/gL approx 0.7 allows the above limits to go
down by half for both vectorlike fermions and flavor bosons. Our model provides
a framework for accommodating neutrino masses and, in the parity symmetric
case, provides a solution to the strong CP problem. The bound on the lepton
flavor gauging scale is somewhat stronger, because of Big Bang Nucleosynthesis
constraints. We argue, however, that the applicability of these constraints
depends on the mechanism at work for the generation of neutrino masses.Comment: 1+23 pages, 1 table, 5 figures. v3: some more textual fixes (main
change: discussion of Lepton Flavor Violating observables rephrased). Matches
journal versio
P, C and Strong CP in Left-Right Supersymmetric Models
We systematically study the connection between P, C and strong CP in the
context of both non-supersymmetric and supersymmetric left-right theories. We
find that the solution to the strong CP problem requires both supersymmetry and
parity breaking scales to be around the weak scale.Comment: 5 pages, RevTex, no figures. Some minor changes, final version as
published in Phys. Rev. Lett. 79, 4744 (1997
Planck-Scale Physics and Solutions to the Strong CP Problem without Axion
We analyse the impact of quantum gravity on the possible solutions to the
strong CP problem which utilize the spontaneously broken discrete symmetries,
such as parity and time reversal invariance. We find that the stability of the
solution under Planck scale effects provides an upper limit on the scale
of relevant symmetry breaking. This result is model dependent and the
bound is most restrictive for the seesaw type models of fermion masses, with
GeV.Comment: 14 pages, LaTex, IC/92/432, UMDHEP 93-105, LMU-16/92 (minor
clarifications in the introduction; missing references are added