659 research outputs found
A Little Higgs Model with Exact Dark Matter Parity
Based on a recent idea by Krohn and Yavin, we construct a little Higgs model
with an internal parity that is not broken by anomalous Wess-Zumino-Witten
terms. The model is a modification of the "minimal moose" models by
Arkani-Hamed et al. and Cheng and Low. The new parity prevents large
corrections to oblique electroweak parameters and leads to a viable dark matter
candidate. It is shown how the complete Standard Model particle content,
including quarks and leptons together with their Yukawa couplings, can be
implemented. Successful electroweak symmetry breaking and consistency with
electroweak precision constraints is achieved for natural paramters choices. A
rich spectrum of new particles is predicted at the TeV scale, some of which
have sizable production cross sections and striking decay signatures at the
LHC.Comment: 25 pp. LaTeX; v2: improved discussion of precision constraints and
references added; v3: summary of model structure added at beginning of sect.
2, version published in JHEP; v4: small correction in Fig.5; v5: correction
to Fig.
Consequences of T-parity breaking in the Littlest Higgs model
In this paper we consider the effects of the T-parity violating anomalous
Wess-Zumino-Witten-Term in the Littlest Higgs model. Apart from tree level
processes, the loop induced decays of the heavy mirror particles into light
standard model fermions lead to a new and rich phenomenology in particular at
breaking scales f below 1 TeV. Various processes are calculated and their
signatures at present and future colliders are discussed. As a byproduct we
find an alternative production mechanism for the Higgs boson.Comment: 30 page
A Possible Arena for Searching New Physics - the Ratio
We propose to investigate flavour changing neutral currents in the transition through the measurement of the difference between and . This is based on
the observation that is due to long distance
physics while arises from the
transition. The effect of mixing is included. A difference in
the decay widths of more than about 30% would be indicative of new physics.Comment: 7 pages, 1 figure include
Minimal Informationally Complete Measurements for Pure States
We consider measurements, described by a positive-operator-valued measure
(POVM), whose outcome probabilities determine an arbitrary pure state of a
D-dimensional quantum system. We call such a measurement a pure-state
informationally complete (PSI-complete) POVM. We show that a measurement with
2D-1 outcomes cannot be PSI-complete, and then we construct a POVM with 2D
outcomes that suffices, thus showing that a minimal PSI-complete POVM has 2D
outcomes. We also consider PSI-complete POVMs that have only rank-one POVM
elements and construct an example with 3D-2 outcomes, which is a generalization
of the tetrahedral measurement for a qubit. The question of the minimal number
of elements in a rank-one PSI-complete POVM is left open.Comment: 2 figures, submitted for the Asher Peres festschrif
Phenomenology of the Little Higgs model with X-Parity
In the popular littlest Higgs model, T-parity can be broken by
Wess-Zumino-Witten (WZW) terms induced by a strongly coupled UV completion. On
the other hand, certain models with multiple scalar multiplets (called moose
models) permit the implementation of an exchange symmetry (X-parity) such that
it is not broken by the WZW terms. Here we present a concrete and realistic
construction of such a model. The little Higgs model with X-Parity is a
concrete and realistic implementation of this idea. In this contribution, the
properties of the model are reviewed and the collider phenomenology is
discussed in some detail. We also present new results on the decay properties
and LHC signatures of the light triplet scalars that are predicted by this
model.Comment: 12 pages, to appear in in the proceedings of the International
Workshop on Beyond the Standard Model Physics and LHC Signatures (BSM-LHC)
and of the 17th International Conference on Supersymmetry and the Unification
of Fundamental Interactions (SUSY09), Boston, USA, 2-4 and 5-10 Jun 200
Ballistic Annihilation
Ballistic annihilation with continuous initial velocity distributions is
investigated in the framework of Boltzmann equation. The particle density and
the rms velocity decay as and , with the
exponents depending on the initial velocity distribution and the spatial
dimension. For instance, in one dimension for the uniform initial velocity
distribution we find . We also solve the Boltzmann equation
for Maxwell particles and very hard particles in arbitrary spatial dimension.
These solvable cases provide bounds for the decay exponents of the hard sphere
gas.Comment: 4 RevTeX pages and 1 Eps figure; submitted to Phys. Rev. Let
`Natural Masslessness Conservation' for neutrinos in two Higgs-doublet models
We present a model which supplements the Standard Electroweak Model with
three right-handed neutrinos and one extra scalar doublet which does not
develop a vacuum expectation value. With the aid of a discrete symmetry the
neutrinos are kept strictly massless. This model has several interesting
features. It has unsuppressed lepton flavour violating processes, in particular
, hinting at the possibility that these may soon be
within experimental reach. The and interactions become non-diagonal at
one loop level. In particular, a non-trivial leptonic mixing matrix is seen to
arise from the clash between the charged gauge boson and the charged scalar
interactions.Comment: (Latex file, 12 pages. Two figures available upon request).
CMU-preprin
Avaliação das características enológicas da cv. Alicante Bouschet produzida em uma região tropical, no Nordeste do Brasil.
O objetivo deste trabalho foi avaliar as características das uvas e do vinho elaborado a partir da cultivar Alicante Bouschet, instalada em fevereiro de 2001 em um solo tipo aluvião, sendo as plantas enxertadas sobre IAC-572 (Vitis caribaea e 101-14 Mgt) e irrigadas por gotejamento
Neutral Heavy Leptons and Electroweak Baryogenesis
We investigate the possibility that baryogenesis occurs during the weak phase
transition in a minimal extension of the Standard Model which contains extra
neutral leptons and conserves total lepton number. The necessary CP-violating
phases appear in the leptonic Yukawa couplings. We compute the CP-asymmetries
in both the neutral and the charged lepton fluxes reflected on the bubble wall.
Using present experimental bounds on the mixing angles and Standard Model
estimates for the parameters related to the scalar potential, we conclude that
it seems unlikely to produce the observed baryon to entropy ratio within this
type of models. We comment on the possibility that the constraints on the
mixings might be naturally relaxed due to small finite temperature effects.Comment: 21 pages (4 Figures
Relations among neutrino observables in the light of a large theta_13 angle
The recent T2K and MINOS indications for a "large" theta_13 neutrino mixing
angle can be accommodated in principle by an infinite number of Yukawa flavour
structures in the seesaw model. Without considering any explicit flavour
symmetry, there is an instructive exercise one can do: to determine the
simplest flavour structures which can account for the data with a minimum
number of parameters, simply assuming these parameters to be uncorrelated. This
approach points towards a limited number of simple structures which show the
minimum complexity a neutrino mass model must generally involve to account for
the data. These basic structures essentially lead to only 4 relations between
the neutrino observables. We emphasize that 2 of these relations, |sin
theta_13|=(tan theta_23/cos delta)*(1-tan theta_12)/(1+tan theta_12) and |sin
theta_13| = sin theta_12 R^1/4, with R= Delta m^2_21/Delta m^2_32, have several
distinctive properties. First, they hold not only with a minimum number of
parameters, but also for complete classes of more general models. Second, any
value of theta_13 within the T2K and MINOS ranges can be obtained from these
relations by taking into account small perturbations. Third, they turn out to
be the pivot relations of models with approximate conservation of lepton
number, which allow the seesaw interactions to induce observable flavour
violating processes, such as mu -> e gamma and tau -> mu gamma. Finally, in
specific cases of this kind, these structures have the rather unique property
to allow a full reconstruction of the seesaw Lagrangian from low energy data.Comment: 13 pages, 3 figure
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