1,537 research outputs found
Limits on a Strong Electroweak Sector from e^+ e^- -> 2gamma + missing E at LEP2
We study the process in the context
of a strong electroweak symmetry breaking model, which can be a source of
events with two photons and missing energy at LEP2. We investigate bounds on
the model assuming that no deviation is observed from the Standard Model within
a given experimental error.Comment: 7 pages, Latex, one figur
Non-standard Dirac adjoint spinor: The emergence of a new dual
In this present communication we provide a new derivation of the Dirac dual
structure by employing a different approach from the originally proposed.
Following a general and rigorous mathematical process to compute the dual
structure, we investigate if is possible to break the existing "rigidity" in
its primordial formulation. For this task, firstly, we look towards to
understand the core of the Dirac spinors construction and then, we suggest to
built an alternative dual structure for the Dirac spinor, which preserve an
invariant norm under any transformation. Finally, we verify
if the prominent physical contents are maintained or if it is affected by such
construction.Comment: 7 pages, 0 figure
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STRONGLY COUPLED ELECTROWEAK SYMMETRY BREAKING: IMPLICATIONS OF MODELS
We discuss the phenomenology of models of dynamical electroweak symmetry
breaking which attempt to generate the observed fermion mass spectrum. After
briefly describing the variety of and constraints on proposed models, we
concentrate on the signatures of colored pseudo-Nambu-Goldstone bosons and
resonances at existing and proposed colliders. These particles provide a
possibly unique signature: strongly produced resonances associated with
electroweak symmetry breaking. (This is the subgroup report for the
``Electroweak Symmetry Breaking and Beyond the Standard Model" working group of
the DPF Long Range Planning Study. This report will appear as a chapter in
``Electroweak Symmetry Breaking and Beyond the Standard Model", edited by T.
Barklow, S. Dawson, H.E. Haber, and J. Siegrist, to be published by World
Scientific.
Outflows, Inflows and Young Stars in the inner 200 pc of the Seyfert galaxy NGC 2110
We present a two-dimensional mapping of stellar population age components,
emission-line fluxes, gas excitation and kinematics within the inner
pc of the Seyfert 2 galaxy NGC 2110. We used the Gemini North Integral Field
Spectrograph (NIFS) in the J and K bands at a spatial resolution of
pc. The unresolved nuclear continuum is originated in combined contributions of
young stellar population (SP; age Myr), a featureless AGN continuum
and hot dust emission. The young-intermediate SP (age Myr) is
distributed in a ring-shaped structure at pc from the nucleus,
which is roughly coincident with the lowest values of the stellar velocity
dispersion. In the inner pc the old SP (age Gyr) is dominant.
The [FeII]1.25m emission-line flux distribution is correlated with the
radio emission and its kinematics comprise two components, one from gas
rotating in the galaxy plane and another from gas in outflow within a bicone
oriented along north-south. These outflows seem to originate in the interaction
of the radio jet with the ambient gas producing shocks that are the main
excitation mechanism of the [FeII] emission. We estimate: (1) an ionized gas
mass outflow rate of M/yr at 70 pc from the nucleus;
and (2) a kinetic power for the outflow of only 0.05% of the AGN bolometric
luminosity implying weak feedback effect on the galaxy.Comment: Accepted for publication in MNRA
Type-4 spinors: transmuting from Elko to single-helicity spinors
In this communication we briefly report an unexpected theoretical discovery
which emerge from the mapping of Elko mass-dimension-one spinors into single
helicity spinors. Such procedure unveils a class of spinor which is classified
as type-4 spinor field within Lounesto classification. In this paper we explore
the underlying physical and mathematical contents of the type-4 spinor.Comment: 9 pages, 0 figure
A new signature for color octet pseudoscalars at the LHC
Color octet (pseudo)scalars, if they exist, will be copiously produced at the
CERN Large Hadron Collider (LHC). However, their detection can become a very
challenging task. In particular, if their decay into a pair of top quarks is
kinematically forbidden, the main decay channel would be into two jets, with a
very large background. In this Brief Report we explore the possibility of using
anomaly-induced decays of the color octet pseudoscalars into gauge bosons to
find them at the LHC.Comment: 4 pages, 2 figures. New references adde
Dangling-bond spin relaxation and magnetic 1/f noise from the amorphous-semiconductor/oxide interface: Theory
We propose a model for magnetic noise based on spin-flips (not
electron-trapping) of paramagnetic dangling-bonds at the
amorphous-semiconductor/oxide interface. A wide distribution of spin-flip times
is derived from the single-phonon cross-relaxation mechanism for a
dangling-bond interacting with the tunneling two-level systems of the amorphous
interface. The temperature and frequency dependence is sensitive to three
energy scales: The dangling-bond spin Zeeman energy delta, as well as the
minimum (E_min) and maximum (E_max) values for the energy splittings of the
tunneling two-level systems. We compare and fit our model parameters to a
recent experiment probing spin coherence of antimony donors implanted in
nuclear-spin-free silicon [T. Schenkel {\it et al.}, Appl. Phys. Lett. 88,
112101 (2006)], and conclude that a dangling-bond area density of the order of
10^{14}cm^{-2} is consistent with the data. This enables the prediction of
single spin qubit coherence times as a function of the distance from the
interface and the dangling-bond area density in a real device structure. We
apply our theory to calculations of magnetic flux noise affecting SQUID devices
due to their Si/SiO_2 substrate. Our explicit estimates of flux noise in SQUIDs
lead to a noise spectral density of the order of 10^{-12}Phi_{0}^{2} {Hz}^{-1}
at f=1Hz. This value might explain the origin of flux noise in some SQUID
devices. Finally, we consider the suppression of these effects using surface
passivation with hydrogen, and the residual nuclear-spin noise resulting from a
perfect silicon-hydride surface.Comment: Final published versio
Gauge Invariance, Color-Octet Vector Resonances and Double Technieta Production at the Tevatron
We show that the usual vector meson dominance method does not apply directly
to the mixing of a color-octet vector boson (color-octet technirho) with the
gluon because of gauge invariance. We propose a gauge invariant method where
one works in a physical basis with mass eigenstate fields. As a result, we show
that the physical technirho does not couple to two gluons, contrary to the
general belief. Consequences for the production of a pair of color-octet,
isosinglet technipions (technietas) at Fermilab is analysed by means of a
simulation of the signal and background, including kinematical cuts. We find
that the signal is too small to be observed.Comment: 14 page
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