1,336 research outputs found
Formation of a strong southward IMF near the solar maximum of cycle 23
International audienceWe analyzed observations of the solar activities and the solar wind parameters associated with large geomagnetic storms near the maximum of solar cycle 23. This analysis showed that strong southward interplanetary magnetic fields (IMFs), formed through interaction between an interplanetary disturbance, and background solar wind or between interplanetary disturbances are an important factor in the occurrence of intense geomagnetic storms. Based on our analysis, we seek to improve our understanding of the physical processes in which large negative Bz's are created which will lead to improving predictions of space weather. Key words. Interplanetary physics (Flare and stream dynamics; Interplanetary magnetic fields; Interplanetary shocks
Effects of quark family nonuniversality in SU(3)_c X SU(4)_L X U(1)_x models
Flavour changing neutral currents arise in the extension of the standard model because anomaly cancellation among the
fermion families requires one generation of quarks to transform differently
from the other two under the gauge group. In the weak basis the distinction
between quark families is meaningless. However, in the mass eigenstates basis,
the Cabibbo-Kobayashi-Maskawa mixing matrix motivates us to classify
left-handed quarks in families. In this sense there are, in principle, three
different assignments of quark weak eigenstates into mass eigenstates. In this
work, by using measurements at the Z-pole, atomic parity violation data and
experimental input from neutral meson mixing, we examine two different models
without exotic electric charges based on the 3-4-1 symmetry, and address the
effects of quark family nonuniversality on the bounds on the mixing angle
between two of the neutral currents present in the models and on the mass
scales and of the new neutral gauge bosons predicted by the
theory. The heaviest family of quarks must transform differently in order to
keep lower bounds on and as low as possible without
violating experimental constraints.Comment: 27 pages, 10 tables, 2 figures. Equation (19) and typos corrected.
Matches version to appear in Phys. Rev.
Democratic Mass Matrices from Broken Flavor Symmetry
We impose flavor symmetry in the supersymmetric
standard model. Three lepton doublets transform as an triplet
and three charged leptons as an triplet, while Higgs
doublets and are singlets. We discuss a
flavor breaking mechanism that leads to "successful"
phenomenological mass matrices, so-called "democratic" ones, in which the large
\n_\mu-\n_\tau mixing is naturally obtained. Three neutrinos have nearly
degenerate masses of order 0.1\eV which may be accesible to future double
\b-decay experiments. We extend our approach to the quark sector and show
that it is well consistent with the observed quark mass hierarchies and the CKM
matrix elements. However, the large mass of the top quark requires a relatively
large coupling. constant.Comment: 12 pages, LaTex file, No figures, minor correction
Electroweak Supersymmetry with an Approximate U(1)_PQ
A predictive framework for supersymmetry at the TeV scale is presented, which
incorporates the Ciafaloni-Pomarol mechanism for the dynamical determination of
the \mu parameter of the MSSM. It is replaced by (\lambda S), where S is a
singlet field, and the axion becomes a heavy pseudoscalar, G, by adding a mass,
m_G, by hand. The explicit breaking of Peccei-Quinn (PQ) symmetry is assumed to
be sufficiently weak at the TeV scale that the only observable consequence is
the mass m_G. Three models for the explicit PQ breaking are given; but the
utility of this framework is that the predictions for all physics at the
electroweak scale are independent of the particular model for PQ breaking. Our
framework leads to a theory similar to the MSSM, except that \mu is predicted
by the Ciafaloni-Pomarol relation, and there are light, weakly-coupled states
in the spectrum. The production and cascade decay of superpartners at colliders
occurs as in the MSSM, except that there is one extra stage of the cascade
chain, with the next-to-LSP decaying to its "superpartner" and \tilde{s},
dramatically altering the collider signatures for supersymmetry. The framework
is compatible with terrestrial experiments and astrophysical observations for a
wide range of m_G and . If G is as light as possible, 300 keV < m_G < 3 MeV,
it can have interesting effects on the radiation energy density during the
cosmological eras of nucleosynthesis and acoustic oscillation, leading to
predictions for N_{\nu BBN} and N_{\nu CMB} different from 3.Comment: 45 pages, 2 colour figures, a reference added, minor correction
Orbifold Family Unification
We study the possibility of complete family unification in higher-dimensional
space-time. Three families of matters in SU(5) grand unified theory are derived
from a single bulk multiplet of SU(N) gauge group (N >= 9) in the framework of
S^1/Z_2 orbifold models. In the case of the direct orbifold breaking down to
the standard model gauge group, there are models in which bulk fields from a
single multiplet and a few brane fields compose three families of quarks and
leptons.Comment: Comments added, version to appear in Physical Review D (v3);
References added (v2); 19 pages (v1
Orbifold Family Unification in SO(2N) Gauge Theory
We study the possibility of family unification on the basis of SO(2N) gauge
theory on the five-dimensional space-time, . Several SO(10),
or SU(5) multiplets come from a single
bulk multiplet of SO(2N) after the orbifold breaking. Other multiplets
including brane fields are necessary to compose three families of quarks and
leptons.Comment: 28 page
A Higher-dimensional Origin of the Inverted Mass Hierarchy for Neutrino
We present successful lepton mass matrices with an inverted mass hierarchy
for neutrinos, which follow from a geometrical structure of a (1+5) dimensional
space-time where two extra dimensions are compactified on the T^2/Z_3 orbifold.
A 5^* and a right-handed neutrino N in each family are localized on each of the
equivalent three fixed points of the orbifold while three 10's and Higgs
doublets H_u and H_d live in the bulk. An S_3 family symmetry is assumed on
three 5^*'s and on three N's, since the three fixed points are equivalent to
one another. The Higgs field \phi responsible for the B-L breaking is localized
on one of the three fixed points, which generates the inverted hierarchy for
the neutrino masses. The baryon asymmetry is well explained in the non-thermal
leptogenesis via inflaton decay. We emphasize that the present model predicts
the effective neutrino mass, _{ee}, responsible for neutrinoless double beta
decays as _{ee}\simeq 50 meV. This will be accessible to future experiments.Comment: 15 page
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