1,954 research outputs found
Flavor Symmetry for Quarks and Leptons
Present data on neutrino masses and mixing favor the highly symmetric
tribimaximal neutrino mixing matrix which suggests an underlying flavor
symmetry. A systematic study of non-abelian finite groups of order
reveals that tribimaximal mixing can be derived not only from the well known
tetrahedral flavor symmetry , but also by using the binary
tetrahedral symmetry which does not contain the
tetrahedral group as a subgroup. has the further advantage that it can
also neatly accommodate the quark masses including a heavy top quark.Comment: 12 pages latex. More typos correcte
Cyclic Universe and Infinite Past
We address two questions about the past for infinitely cyclic cosmology. The
first is whether it can contain an infinite length null geodesic into the past
in view of the Borde-Guth-Vilenkin (BGV) "no-go" theorem, The second is
whether, given that a small fraction of spawned universes fail to cycle, there
is an adequate probability for a successful universe after an infinite time. We
give positive answers to both questions then show that in infinite cyclicity
the total number of universes has been infinite for an arbitrarily long time.Comment: 7 pages. Clarification in discussion of infinite pas
Aspects of Soft and Spontaneous CP Violation
We study four different models for CP violation: the standard (KM) model, the
aspon model of spontaneous breaking and two models of soft breaking. In all
except the standard model, the strong CP problem is addressed and solved.
Testable predictions for the area of the unitarity triangle and for
(epsilon'/epsilon)_K are emphasized. The issue of CP violation may well become
the first place where the standard model of particle theory is shown
definitively to be deficient. There are two reasons for expecting this to
happen: (1) the strong CP problem is still not understood in the unadorned
standard model and (2) the KM mechanism, although unquestionably present, may
not provide the full explanation of epsilon_K and (epsilon'/epsilon)_K.Comment: 24 pages LaTeX including 4 figures. Minor modification to analysis of
lower bound for d_n, summarized in new Table I
Gravitation at Very Short Distances
In this note, it is discussed why attempts to renormalize conventional
quantum gravity may be based on a false presumption, because, according to
Verlinde's entropic view of gravity, the gravitational force between two
elementary particles vanishes.Comment: 5 pages. Additional reference
Production of doubly charged vector bilepton pairs at colliders
The production of pairs of doubly charged vector bileptons is studied at
future colliders. The unpolarized cross--section for the
subprocess is analytically calculated and
convoluted to predict the number of events in the complete process. The gauge or non--gauge character of the
vector bilepton is discussed. It is found that as a consequence
of its spectacular signature, as it decays dominantly into two identical
charged leptons, and also due to its charge contents, which significantly
enhance the cross--section, the detection of this class of particles with mass
in the sub--TeV region can be at the reach of these colliders. The
model--independent nature of our results is stressed.Comment: 9 pages, 7 figures, submitted to physical review
The exact eigenstates of the neutrino mass matrix without CP-phase violation
In this paper we obtain the exact mass-eigenstates of the Majorana physical
neutrinos. We start by taking into account a general mass matrix
without any CP-phase violation. It is then diagonalized by exactly solving an
appropriate set of equations. The solution supplies straightforwardly the mass
eigenvalues depending on the diagonal entries and mixing angles. Finally, the
consequences of these analytical expressions are discussed assuming various
phenomenological restrictions such as conserving the global lepton number
and the interchange symmetry. The minimal
absolute mass in the neutrino sector is also obtained since the two plausible
scenarios invoked above are employed.Comment: 9 pages, no figure
Inverted neutrino mass hierarchies from U(1) symmetries
Motivated by effective low energy models of string origin, we discuss the
neutrino masses and mixing within the context of the Minimal Supersymmetric
Standard Model supplemented by a U(1) anomalous family symmetry and additional
Higgs singlet fields charged under this extra U(1). In particular, we interpret
the solar and atmospheric neutrino data assuming that there are only three
left-handed neutrinos which acquire Majorana masses via a lepton number
violating dimension-five operator. We derive the general form of the charged
lepton and neutrino mass matrices when two different pairs of singlet Higgs
fields develop non--zero vacuum expectation values and show how the resulting
neutrino textures are related to approximate lepton flavor symmetries. We
perform a numerical analysis for one particular case and obtain solutions for
masses and mixing angles, consistent with experimental data.Comment: 15 pages, 4 figure
Axion and neutrino physics from anomaly cancellation
It has been recently shown that the requirement of anomaly cancellation in a
(non-supersymmetric) six-dimensional version of the standard model fixes the
field content to the known three generations. We discuss the phenomenological
consequences of the cancellation of the local anomalies: the strong CP problem
is solved and the fundamental scale of the theory is bounded by the physics of
the axion. Neutrinos acquire a mass in the range suggested by atmospheric
experiments.Comment: 9 pages, RevTeX
Top quark forward-backward asymmetry and charge asymmetry in left-right twin Higgs model
In order to explain the Tevatron anomaly of the top quark forward-backward
asymmetry in the left-right twin Higgs model, we choose to give up
the lightest neutral particle of field as a stable dark matter
candidate. Then a new Yukawa interaction for is allowed, which can be
free from the constraint of same-sign top pair production and contribute
sizably to . Considering the constraints from the production rates of
the top pair (), the top decay rates and invariant mass
distribution, we find that this model with such new Yukawa interaction can
explain measured at the Tevatron while satisfying the charge
asymmetry measured at the LHC.Moreover, this model predicts a
strongly correlation between at the LHC and at the
Tevatron, i.e., increases as increases.Comment: 17 pages, 9 figures; matches the published versio
Proton Decay and Related Processes in Unified Models with Gauged Baryon Number:
In unification models based on SU(15) or SU(16), baryon number is part of the
gauge symmetry, broken spontaneously. In such models, we discuss various
scenarios of important baryon number violating processes like proton decay and
neutron-antineutron oscillation. Our analysis depends on the effective operator
method, and covers many variations of symmetry breaking, including different
intermediate groups and different Higgs boson content. We discuss processes
mediated by gauge bosons and Higgs bosons parallely. We show how accidental
global or discrete symmetries present in the full gauge invariant Lagrangian
restrict baryon number violating processes in these models. In all cases, we
find that baryon number violating interactions are sufficiently suppressed to
allow grand unification at energies much lower than the usual GeV.Comment: (32 pages LATEX) [DOE-ER\,40757-022, CPP-93-22] {Small changes made
and two references added. This version will appear in Phys. Rev. D
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