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 $U(1)_H$ family symmetry. The model is based on the left-right gauge group with an additional $Z_4$ 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 $E_6$. 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 $\Lambda$ of relevant symmetry breaking. This result is model dependent and the bound is most restrictive for the seesaw type models of fermion masses, with $\Lambda < 10^6$ GeV.Comment: 14 pages, LaTex, IC/92/432, UMDHEP 93-105, LMU-16/92 (minor clarifications in the introduction; missing references are added