An Improved Supersymmetric SU(5)

By supplementing minimal supersymmetric SU(5) (MSSU(5)) with a flavor ${\cal U}(1)$ symmetry and two pairs of $\bar{15}+15$ `matter' supermultiplets, we present an improved model which explains the charged fermion mass hierarchies and the magnitudes of the CKM matrix elements, while avoiding the undesirable asymptotic mass relations $m_s=m_{\mu}, m_d/m_s = m_e/m_{\mu}$. The strong coupling $\alpha_s (M_Z)$ is predicted to be approximately 0.115, and the proton lifetime is estimated to be about five times larger than the MSSU(5) value. The atmospheric and solar neutrino puzzles are respectively resolved via maximal $\nu_{\mu}-\nu_{\tau}$ and small mixing angle $\nu_e-\nu_s$ MSW oscillations, where $\nu_s$ denotes a sterile neutrino. The ${\cal U}(1)$ symmetry ensures not only a light $\nu_s$ but also automatic `matter' parity.Comment: 11 pp. LATEX. Version with minor addition accepted for publication in Physics Letters

R-Parity Violation: Origin of μ\mu -Term and Other Consequences

We propose a new mechanism in which the generation of the supersymmetric $\mu$-term as well charged lepton masses is closely tied to R-parity violation involving heavy vector-like families . A realistic example based on $SU(3)_c\times SU(2)_L\times U(1)_Y$, supplemented by the symmetry ${\cal R}\times {\cal U}(1)$, is presented, where ${\cal R}$ (${\cal U}(1)$) denotes a continuous $R$ (flavor) symmetry. In addition to the $\mu$-term, the charged fermion mass hierarchies and mixings, as well as baryon number conservation are also nicely explained. Bilinear R-parity violating coupling involving the first generation gives rise to neutrino mass relevant for the small angle $\nu_e-\nu_s$ MSW oscillations, where $\nu_s$ denotes a sterile state. The atmospheric neutrino puzzle is resolved via maximal mixing angle $\nu_{\mu }-\nu_{\tau}$ oscillations. The decay of the lightest neutralino (LSP) and leptogenesis are briefly discussed.Comment: 20 pp. LATE

WIMP Dark Matter Inflation with Observable Gravity Waves

We present a successful inflation model based on $\lambda \phi^4$ potential in which a Standard Model (SM) singlet inflaton $\phi$, with mass of around a TeV or less, also plays the role of a weakly interacting scalar dark matter particle (WIMP). The WIMP relic abundance generated after inflation is in accord with the current observations. The spectral index $n_s$ lies within the WMAP 1-$\sigma$ bounds, while the Planck satellite may observe the tensor-to-scalar ratio, a canonical measure of gravity waves, which we estimate lies between 0.003 and 0.007.An unbroken $Z_2$ parity ensures that the scalar WIMP is absolutely stable.Comment: 4 pages, 2 figures, Note Added which includes a brief discussion of two previous works on the same model considered in our pape

Anomalous U(1): Solving Various Puzzles Of MSSM And SU(5) GUT

We discuss how an anomalous U(1) symmetry when appended to MSSM and SUSY GUTs [e.g. SU(5)] can help overcome a variety of puzzles related to charged fermion masses and mixings, flavor changing processes, proton decay and neutrino oscillations. Proton lifetime for SU(5) GUT, in particular, is predicted in a range accessible to the ongoing or planned searches.Comment: Presented at NOON2001 Workshop, Kashiwa, Japan, 5-8 Dec. 200

Gravity Waves and Gravitino Dark Matter in μ\mu-Hybrid Inflation

We propose a novel reformulation of supersymmetric (more precisely $\mu$-) hybrid inflation based on a local U(1) or any suitable extension of the minimal supersymmetric standard model (MSSM) which also resolves the $\mu$ problem. We employ a suitable Kahler potential which effectively yields quartic inflation with non-minimal coupling to gravity. Imposing the gravitino Big Bang Nucleosynthesis (BBN) constraint on the reheat temperature ($T_r \lesssim 10^6$ GeV) and requiring a neutralino LSP, the tensor to scalar ratio ($r$) has a lower bound $r \gtrsim 0.004$. The U(1) symmetry breaking scale lies between $10^8$ and $10^{12}$ GeV. We also discuss a scenario with gravitino dark matter whose mass is a few GeV.Comment: 5 pages, 4 figures, revised version to appear in Physics Letters

Coannihilation Scenarios and Particle Spectroscopy in SU(4)_c x SU(2)_L x SU(2)_R

We identify a variety of coannihilation scenarios in a supersymmetric SU(4)_c x SU(2)_L x SU(2)_R model with discrete left-right symmetry. Non-universal gaugino masses, compatible with the gauge symmetry, play an essential role in realizing gluino and bino-wino coannihilation regions that are consistent with the WMAP dark matter constraints. We also explore regions of the parameter space in which the little hierarchy problem is partially resolved. We present several phenomenologically interesting benchmark points and the associated sparticle and Higgs mass spectra.Comment: 16 pages, 5 figures and 1 tabl