368 research outputs found

### Atmospheric and Solar Neutrino Oscillations in \nuMSSM and Beyond

We show how a unified description of the various two-flavor neutrino
oscillation solutions, allowed by the atmospheric and solar neutrino
experiments, are naturally realized within the framework of $\nu$MSSM (MSSM
augmented with the seesaw mechanism) and beyond, especially grand unified
theories. A general mechanism for achieving maximal mixing to resolve the
atmospheric anomaly is discussed, and applied to the flipped SU(5) model.
Except in the case of MSSM and SU(5), a light sterile neutrino is an inevitable
consequence of our considerations. The bi-maximal neutrino mixing scenario is
one of the options considered. Neutrino hot dark matter can arise in models
with maximal $\nu_{\mu}-\nu_s$ oscillations. A ${\cal U}(1)$ flavor symmetry,
motivated by the charged fermion mass hierarchies and the magnitudes of the CKM
matrix elements, plays a central role.Comment: 14 pp, LATEX. Typos are corrected, possibilities of the neutrino HDM
in various scenarios are emphasize

### Gravity Waves and Gravitino Dark Matter in $\mu$-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

### \theta_13, Rare Processes and Proton Decay in Flipped SU(5)

We consider an extended flipped SU(5) model, supplemented by a flavor ${\cal
U}(1)$ symmetry, which yields bi-large neutrino mixings, charged fermion mass
hierarchies and CKM mixings. The third leptonic mixing angle \te_{13} turns
out to lie close to 0.07, and neutrino CP violation can be estimated from the
observed baryon asymmetry. For lepton flavor violating processes we find the
branching ratios, {\rm BR}(\mu \to e\ga)\sim {\rm BR}(\tau \to e \ga) \sim
10^{-4}\cdot {\rm BR}(\tau \to \mu \ga) \stackrel{<}{_\sim}5\cdot 10^{-14}.
The proton lifetime $\tau_{p\to \pi^0 e^{+}}\simeq 10^{34}-10^{36}$ yrs.Comment: Discussion on leptogenesis and CP violation, and references adde

### Higgs Inflation, Seesaw Physics and Fermion Dark Matter

We present an inflationary model in which the Standard Model Higgs doublet
field with non-minimal coupling to gravity drives inflation, and the effective
Higgs potential is stabilized by new physics which includes a dark matter
particle and right-handed neutrinos for the seesaw mechanism. All of the new
particles are fermions, so that the Higgs doublet is the unique inflaton
candidate. With central values for the masses of the top quark and the Higgs
boson, the renormalization group improved Higgs potential is employed to yield
the scalar spectral index $n_s \simeq 0.968$, the tensor-to-scalar ratio $r
\simeq 0.003$, and the running of the spectral index $\alpha=dn_s/d \ln k
\simeq -5.2 \times 10^{-4}$ for the number of e-folds $N_0=60$ ($n_s \simeq
0.962$, $r \simeq 0.004$, and $\alpha \simeq -7.5 \times 10^{-4}$ for
$N_0=50$). The fairly low value of $r \simeq 0.003$ predicted in this class of
models means that the ongoing space and land based experiments are not expected
to observe gravity waves generated during inflation.
[Dedicated to the memory of Dr. Paul Weber (1947 - 2015). Paul was an
exceptional human being and a very special friend who will be sorely missed.]Comment: 15 pages, 3 figure

### Bi-maximal Neutrino Mixings And Proton Decay In SO(10) With Anomalous Flavor ${\cal U}(1)$

By supplementing supersymmetric SO(10) with an anomalous ${\cal U}(1)$ flavor
symmetry and additional `matter' superfields carrying suitable ${\cal U}(1)$
charges, we explain the charged fermion mass hierarchies, the magnitudes of the
CKM matrix elements, as well as the solar and atmospheric neutrino data. We
stress bi-maximal vacuum neutrino mixings, and indicate how the small or large
mixing angle MSW solution can be incorporated. The ${\cal U}(1)$ symmetry also
implies that $\tau_{p\to K\nu}[SO(10)]\sim (10-100)\cdot \tau_{p\to K\nu}[{\rm
minimal}~SU(5)]$.Comment: 4 pages, revte

### 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

### From Hybrid to Quadratic Inflation With High-Scale Supersymmetry Breaking

Motivated by the reported discovery of inflationary gravity waves by the
BICEP2 experiment, we propose an inflationary scenario in supergravity, based
on the standard superpotential used in hybrid inflation. The new model yields a
tensor-to-scalar ratio r ~ 0.14 and scalar spectral index ns ~ 0.964,
corresponding to quadratic (chaotic) inflation. The important new ingredients
are the high-scale, (1.6-10) x 10^13 GeV, soft supersymmetry breaking mass for
the gauge singlet inflaton field and a shift symmetry imposed on the K\"ahler
potential. The end of inflation is accompanied, as in the earlier hybrid
inflation models, by the breaking of a gauge symmetry at (1.2-7.1) x 10^16 GeV,
comparable to the grand-unification scale.Comment: Version with minor corrections to appear in PL

### 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

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