No Arabic abstract
We present a supersymmetric extension of the Standard Model with a gauged SU(2) family symmetry for the leptons. It is shown that this family symmetry can be consistently broken at the TeV scale along with supersymmetry. If supersymmetry breaking is driven by anomaly mediation, this model can provide positive squared masses for the sleptons and thus cure the tachyon problem. We analyze the constraints and consequences of this scenario. A characteristic feature of this model is the non-degeneracy of the first two family sleptons. The model predicts large value of tan(beta) and observable tau to e gamma and B to mu^+ mu^- decay rates.
We consider extension of the standard model $SU(2)_l times SU(2)_h times U(1)$ where the first two families of quarks and leptons transform according to the $SU(2)_l$ group and the third family according to the $SU(2)_h$ group. In this approach, the largeness of top-quark mass is associated with the large vacuum expectation value of the corresponding Higgs field. The model predicts almost degenerate heavy $W$ and $Z$ bosons with non-universal couplings, and extra Higgs bosons. We present in detail the symmetry breaking mechanism, and carry out the subsequent phenomenology of the gauge sector. We compare the model with electroweak precision data, and conclude that the extra gauge bosons and the Higgs bosons whose masses lie in the TeV range, can be discovered at the LHC.
We discuss proton decay in a recently proposed model of supersymmetric hybrid inflation based on the gauge symmetry $SU(4)_c times SU(2)_L times SU(2)_R$. A $U(1), R$ symmetry plays an essential role in realizing inflation as well as in eliminating some undesirable baryon number violating operators. Proton decay is primarily mediated by a variety of color triplets from chiral superfields, and it lies in the observable range for a range of intermediate scale masses for the triplets. The decay modes include $p rightarrow e^{+}(mu^+) + pi^0$, $p rightarrow bar{ u} + pi^{+}$, $p rightarrow K^0 + e^+(mu^{+})$, and $p rightarrow K^+ + bar{ u}$, with a lifetime estimate of order $10^{34}-10^{36}$ yrs and accessible at Hyper-Kamiokande and future upgrades. The unification at the Grand Unified Theory (GUT) scale $M_{rm GUT}$ ($sim 10^{16}$ GeV) of the Minimal Supersymmetric Standard Model (MSSM) gauge couplings is briefly discussed.
We show how the SUSY flavour and CP problems can be solved using gauged SU(3) family symmetry previously introduced to describe quark and lepton masses and mixings, in particular neutrino tri-bimaximal mixing via constrained sequential dominance. The Yukawa and soft trilinear and scalar mass squared matrices and kinetic terms are expanded in powers of the flavons used to spontaneously break the SU(3) family symmetry, and the canonically normaliz
We consider an extended gauge group for the electroweak interaction: SU(2)_1 times SU(2)_2 times U(1)_Y where the first and second generations of fermions couple to SU(2)_1 while the third generation couples to SU(2)_2. Bounds based on precision observables and heavy gauge boson searchesare placed on the new parameters of the theory, and the potential of the theory to explain R_b and R_c is explored. We investigate processes that could produce observable signals at the LHC and NLC.
We consider the extended electroweak gauge group SU(2)_1 times SU(2)_2 times U(1)_Y where the first and second families of fermions couple to SU(2)_1 while the third family couples to SU(2)_2. Bounds based an precision electroweak observables and heavy gauge boson searches are placed on the new parameters of the theory. The extra gauge bosons can be as light as about a TeV and can be discovered at future colliders such as the NLC and LHC for a wide range of the parameter space. FCNC interactions are also considered.