1,788 research outputs found
On Composite Two Higgs Doublet Models
We investigate composite two Higgs doublet models realized as pseudo
Goldstone modes, generated through the spontaneous breaking of a global
symmetry due to strong dynamic at the TeV scale. A detailed comparative survey
of two possible symmetry breaking patterns, SU(5) -> SU(4) x U(1) and SU(5) x
SU(4), is made. We point out choices for the Standard Model fermion
representations that can alleviate some phenomenological constraints, with
emphasis towards a simultaneous solution of anomalous Zb\bar{b} coupling and
Higgs mediated Flavor Changing Neutral Currents. We also write down the kinetic
lagrangian for several models leading to Two Higgs Doublets and identify the
anomalous contributions to the T parameter. Moreover, we describe a model based
on the breaking in which there is no tree-level breaking of
custodial symmetry, discussing also the possible embeddings for the fermion
fields.Comment: 17 pages. Mistake corrected, added one section on a T- and flavor
safe model based on SO(9)/SO(8). Matches published versio
Can Inflation Induce Supersymmetry Breaking in a Metastable Vacuum?
We argue that fields responsible for inflation and supersymmetry breaking are
connected by gravitational couplings. In view of the recent progress in
studying supersymmetry breaking in a metastable vacuum, we have shown that in
models of supersymmetric hybrid inflation, where R-symmetry plays an important
role, the scale of supersymmetry breaking is generated dynamically at the end
of inflation and turns out to be consistent with gravity mediation.Comment: 5 pages, Latex, Footnote and references added, Journal versio
SQCD Inflation & SUSY Breaking
A model of generalised hybrid inflation in a supersymmetric QCD theory is
proposed whose parameters are the gauge coupling and quark masses. Its
gravitational coupling to another SQCD sector induces a metastable
supersymmetry breaking vacuum of the ISS type as ISS quarks become massive at
the end of inflation. Using a known mechanism with a gravitational breaking of
the baryon number and the gauging of flavour symmetries, we find that gauge
mediation of supersymmetry breaking is compatible with the dynamics of the
inflation sector. Reheating proceeds via the thermalization of the ISS
messengers into the standard model states. This setup contains a single
dimensionful parameter in the form of a quark mass term in the inflationary
sector, i.e. all other scales involved are either related to this single mass
parameter or dynamically generated.Comment: 15 pages, typos corrected, references adde
Intermediate Scale Inflation and Metastable Supersymmetry Breaking
We investigate the possibility of obtaining a low scale of supersymmetry
breaking within the ISS framework using a metastable vacuum. This is achieved
by introducing an R-symmetry preserving gravitational coupling of the ISS
sector to a relatively low scale inflationary sector. We find the allowed range
for the supersymmetry breaking scale, 10^4 GeV < \mu < 10^8 GeV, which is low
enough to be amenable to gauge supersymmetry breaking mediation. This scenario
is based upon a so-called hilltop inflation phase whose initial condition
problem is also addressed.Comment: 6 pages, Latex, typos corrected, references adde
Exotic particles below the TeV from low scale flavour theories
A flavour gauge theory is observable only if the symmetry is broken at
relatively low energies. The intrinsic parity-violation of the fermion
representations in a flavour theory describing quark, lepton and higgsino
masses and mixings generically requires anomaly cancellation by new fermions.
Benchmark supersymmetric flavour models are built and studied to argue that: i)
the flavour symmetry breaking should be about three orders of magnitude above
the higgsino mass, enough also to efficiently suppress FCNC and CP violations
coming from higher-dimensional operators; ii) new fermions with exotic decays
into lighter particles are typically required at scales of the order of the
higgsino mass.Comment: 19 pages, references added, one comment and one footnote added,
results unchange
Inflation, moduli (de)stabilization and supersymmetry breaking
We study the cosmological inflation from the viewpoint of the moduli
stabilization. We study the scenario that the superpotential has a large value
during the inflation era enough to stabilize moduli, but it is small in the
true vacuum. This scenario is discussed by using a simple model, one type of
hybrid models.Comment: 17 pages, 7 figure
Quark-Lepton Unification and Eight-Fold Ambiguity in the Left-Right Symmetric Seesaw Mechanism
In many extensions of the Standard Model, including a broad class of
left-right symmetric and Grand Unified theories, the light neutrino mass matrix
is given by the left-right symmetric seesaw formula , in which the right-handed neutrino mass
matrix and the triplet couplings are proportional to the same matrix
f. We propose a systematic procedure for reconstructing the solutions (in
the n-family case) for the matrix f as a function of the Dirac neutrino
couplings and of the light neutrino mass parameters, which can
be used in both analytical and numerical studies. We apply this procedure to a
particular class of supersymmetric SO(10) models with two 10-dimensional and a
pair of representations in the Higgs sector, and study the
properties of the corresponding 8 right-handed neutrino spectra. Then, using
the reconstructed right-handed neutrino and triplet parameters, we study
leptogenesis and lepton flavour violation in these models, and comment on
flavour effects in leptogenesis in the type I limit. We find that the mixed
solutions where both the type I and the type II seesaw mechanisms give a
significant contribution to neutrino masses provide new opportunities for
successful leptogenesis in SO(10) GUTs.Comment: 31 pages, 32 figures. Appendix augmented with useful analytic
formulae, a few typos corrected, 2 references adde
Large Solar Angle and Seesaw Mechanism: a Bottom-up Perspective
In addition to the well established large atmospheric angle, a large solar
angle is probably present in the leptonic sector. In the context of the see-saw
and by means of a bottom-up approach, we explore which patterns for the Dirac
and Majorana right-handed mass matrices provide two large mixings in a robust
way and with the minimal amount of tuning. Three favourite patterns emerge,
which have a suggestive physical interpretation in terms of the role played by
right-handed neutrinos: in both solar and atmospheric sectors, either a single
or a pseudo-Dirac pair of right-handed neutrinos dominates. Each pattern gives
rise to specific relations among the neutrino mixing angles and mass
differences, which lead to testable constraints on U_{e3}. The connection with
the rate of LFV charged lepton decays is also addressed.Comment: 31 pages, 7 figures; published versio
HIGGS PHENOMENOLOGY OF THE SUPERSYMMETRIC MODEL WITH A GAUGE SINGLET
We discuss the Higgs sector of the supersymmetric standard model extended by
a gauge singlet for the range of parameters, which is compatible with universal
soft supersymmetry breaking terms at the GUT scale. We present results for the
masses, couplings and decay properties of the lightest Higgs bosons, in
particular with regard to Higgs boson searches at LEP. The prospects differ
significantly from the ones within the MSSM.Comment: 12 pages (Plain Tex), 7 fig
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