1,149 research outputs found
Dynamical CP Violation in Composite Higgs Models
The dynamical origin of the CP violation in electroweak theory is
investigated in composite Higgs models. The mechanism of the spontaneous CP
violation proposed in other context by Dashen is adopted to construct simple
models of the dynamical CP violation.
Within the models the size of the neutron electric dipole moment is estimated
and the constraint on the -parameter in K-meson decays is
discussed.Comment: 20 pages, 2 figures not included, uses LaTeX, HUPD-922
A screening mechanism for extra W and Z gauge bosons
We generalize a previous construction of a fermiophobic model to the case of
more than one extra and gauge bosons. We focus in particular on the
existence of screening configurations and their implication on the gauge boson
mass spectrum. One of these configurations allows for the existence of a set of
relatively light new gauge bosons, without violation of the quite restrictive
bounds coming from the parameter. The links with Bess and
degenerate Bess models are also discussed. Also the signal given here by this
more traditional gauge extension of the SM could help to disentangle it from
the towers of Kaluza-Klein states over and gauge bosons in extra
dimensions.Comment: 23 pages, 1 figure, extended discussion on precision tests. To appear
in International Journal of Modern Physics
Condutitvidade hisráulica do solo coeso dos tabuleiros costeiros cultivado com citros.
Avalia através da determinação da condutividade hidráulica não saturada, o movimento de água em agrissolo acinzentado coeso dos tabuleiros costeiros cultivado com citros.bitstream/CPATC/19569/1/bp-22.pdfISSN 1678-1961
Many-nodes/many-links spinfoam: the homogeneous and isotropic case
I compute the Lorentzian EPRL/FK/KKL spinfoam vertex amplitude for regular
graphs, with an arbitrary number of links and nodes, and coherent states peaked
on a homogeneous and isotropic geometry. This form of the amplitude can be
applied for example to a dipole with an arbitrary number of links or to the
4-simplex given by the compete graph on 5 nodes. All the resulting amplitudes
have the same support, independently of the graph used, in the large j (large
volume) limit. This implies that they all yield the Friedmann equation: I show
this in the presence of the cosmological constant. This result indicates that
in the semiclassical limit quantum corrections in spinfoam cosmology do not
come from just refining the graph, but rather from relaxing the large j limit.Comment: 8 pages, 4 figure
Scattering and self-adjoint extensions of the Aharonov-Bohm hamiltonian
We consider the hamiltonian operator associated with planar sec- tions of
infinitely long cylindrical solenoids and with a homogeneous magnetic field in
their interior. First, in the Sobolev space , we characterize all
generalized boundary conditions on the solenoid bor- der compatible with
quantum mechanics, i.e., the boundary conditions so that the corresponding
hamiltonian operators are self-adjoint. Then we study and compare the
scattering of the most usual boundary con- ditions, that is, Dirichlet, Neumann
and Robin.Comment: 40 pages, 5 figure
A Tumbling Top-Quark Condensate Model
We propose a renormalizable model with no fundamental scalars which breaks
itself in the manner of a "tumbling" gauge theory down to the standard model
with a top-quark condensate. Because of anomaly cancellation requirements, this
model contains two color sextet fermions (quixes), which are vector-like with
respect to the standard model gauge group. The model also has a large number of
pseudo-Nambu-Goldstone bosons, some of which can be light. The top-quark
condensate is responsible for breaking the electroweak gauge symmetry and gives
the top quark a large mass. We discuss the qualitative features and instructive
shortcomings of the model in its present form. We also show that this model can
be naturally embedded into an aesthetically pleasing model in which the
standard model fermion families appear symmetrically.Comment: 16 pages. v2: TeX formatting fixed, no other change
R parity violating contribution to
In this article we consider the contribution of violating couplings to
the process at high energy lepton collider.
We show that the present upper bound on the relevant violating coulpings
obtained from low energy measurements would produce a few hundred to a thousand
top-charm events at the next linear collider. Hence, it
should be possible to observe the rare process at future lepton collider.Comment: LaTEX, 13 pages, one figure is removed. A brief discussion on
possible backgrounds is added. To appear in Phys. Rev.
Measurement of the 6S-7S transition polarizablility in atomic cesium and an improved test of the standard model
The ratio of the off-diagonal hyperfine amplitude to the tensor transition
polarizability (Mhf/beta) for the 6S-7S transition in cesium has been measured.
The value of beta=27.024(43)(expt)(67)(theory)a_0^3 is then obtained using an
accurate semi-empirical value of Mhf. This is combined with a previous
measurement of parity nonconservation in atomic cesium and previous atomic
structure calculations to determine the value of the weak charge. The
uncertainties in the atomic structure calculations are updated (and reduced) in
light of new experimental tests. The result Q_W=-72.06(28)(expt) (34)(theory)
differs from the prediction of the standard model of elementary particle
physics by 2.5 sigma.Comment: 12 pages, 1 figur
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