127 research outputs found
Electroweak constraints on warped models with custodial symmetry
It has been recently argued that realistic models with warped extra
dimensions can have Kaluza-Klein particles accessible at the Large Hadron
Collider if a custodial symmetry, SU(2)_V \times P_{LR}, is used to protect the
T parameter and the coupling of the left-handed bottom quark to the Z gauge
boson. In this article we emphasize that such a symmetry implies that the loop
corrections to both the T parameter and the Z b_L \bar{b}_L coupling are
calculable. In general, these corrections are correlated, can be sizable, and
should be considered to determine the allowed parameter space region in models
with warped extra dimensions and custodial symmetry, including Randall-Sundrum
models with a fundamental Higgs, models of gauge-Higgs unification and
Higgsless models. As an example, we derive the constraints that arise on a
representative model of gauge-Higgs unification from a global fit to the
precision electroweak observables. A scan over the parameter space typically
leads to a lower bound on the Kaluza-Klein excitations of the gauge bosons of
about 2-3 TeV, depending on the configuration. In the fermionic sector one can
have Kaluza-Klein excitations with masses of a few hundred GeV. We present the
constraints on these light fermions from recent Tevatron searches, and explore
interesting discovery channels at the LHC.Comment: 38 pages, 8 figure
Proton Stability in Six Dimensions
We show that Lorentz and gauge invariance explain the long proton lifetime
within the standard model in six dimensions. The baryon-number violating
operators have mass dimension 15 or higher. Upon TeV-scale compactification of
the two universal extra dimensions on a square orbifold, a discrete
subgroup of the 6-dimensional Lorentz group continues to forbid dangerous
operators.Comment: PRL accepted versio
Opaque Branes in Warped Backgrounds
We examine localized kinetic terms for gauge fields which can propagate into
compact, warped extra dimensions. We show that these terms can have a relevant
impact on the values of the Kaluza-Klein (KK) gauge field masses, wave
functions, and couplings to brane and bulk matter. The resulting
phenomenological implications are discussed. In particular, we show that the
presence of opaque branes, with non-vanishing brane-localized gauge kinetic
terms, allow much lower values of the lightest KK mode than in the case of
transparent branes. Moreover, we show that if the large discrepancies among the
different determinations of the weak mixing angle would be solved in favor of
the value obtained from the lepton asymmetries, bulk electroweak gauge fields
in warped-extra dimensions may lead to an improvement of the agreement of the
fit to the electroweak precision data for a Higgs mass of the order of the weak
scale and a mass of the first gauge boson KK excitation most likely within
reach of the LHC.Comment: 37 pages, 12 figures, improved analysis of the precision electroweak
constraint
TP87 153. Implantación de dos sistemas de oxigenador de membrana extracorpórea a un paciente en dos ingresos: Uno como recuperación, otro como puente a otra asistencia
IntroducciónLos programas de asistencias mecánicas de corta duración se empiezan a desarrollar en nuestro país. Uno de los más utilizados es el oxigenador de membrana extracor-pórea (ECMO), cuya mayor indicación en nuestro entorno es como puente al trasplante. Presentamos un caso en el que se coloca como recuperación, y tras 3 meses otra nueva como puente a otra asistencia.Material y métodosPaciente de 61 años que ingresa por trombosis de stent en descendente anterior (DA), presentando shock cardiogénico refractario a fármacos y balón de contrapulsación. Dada la situación se coloca ECMO venoarterial que se retira a las 72h por mejoría, dándose de alta el paciente a los 19 días.Tres meses después el paciente ingresa con bajo gasto y edema de pulmón, implantándose un ECMO venoarterial en el box de intensivos como puente a asistencia univentricular Levitronix, que se coloca 10h después en quirófano. Se reinterviene dos veces por taponamiento y se extuba a los 7 días, momento en que se incluye en alarma 0. Tras 27 días con Levitronix izquierda, la paciente sufre un ictus y retiramos de lista, falleciendo la paciente.ResultadosLos dos ECMO cumplieron su objetivo: uno de recuperación y el otro de puente a la asistencia.ConclusionesComo describimos en este caso, el ECMO es muy útil y fácil de implantar en pacientes con el objetivo de la recuperación o como puente al trasplante. Las asistencias no están exentas de complicaciones
Clinical significance of the detection of Candida albicans germ tube-specific antibodies in critically ill patients
AbstractThe present study, comprising a prospective multicentre study including 53 non-neutropenic patients from intensive care units (ICU) in six Spanish tertiary-care hospitals, was carried out to determine the clinical significance and influence on mortality of Candida albicans germ tube-specific antibodies (CAGTA). There were 22 patients (41.5%) for whom the CAGTA results were positive, although none of had a blood culture positive for Candida. The intra-ICU mortality rate was significantly lower (p = 0.004) in CAGTA-positive patients (61.2% vs. 22.7%). Multivariate analysis confirmed that a positive CAGTA result was the only protective factor to be independently associated with ICU mortality (β coefficient = −0.3856; 95% confidence interval = −0.648 to −0.123)
The GUT Scale and Superpartner Masses from Anomaly Mediated Supersymmetry Breaking
We consider models of anomaly-mediated supersymmetry breaking (AMSB) in which
the grand unification (GUT) scale is determined by the vacuum expectation value
of a chiral superfield. If the anomaly-mediated contributions to the potential
are balanced by gravitational-strength interactions, we find a
model-independent prediction for the GUT scale of order . The GUT threshold also affects superpartner masses, and can easily
give rise to realistic predictions if the GUT gauge group is asymptotically
free. We give an explicit example of a model with these features, in which the
doublet-triplet splitting problem is solved. The resulting superpartner
spectrum is very different from that of previously considered AMSB models, with
gaugino masses typically unifying at the GUT scale.Comment: 17 page
Effective Lagrangians and Light Gravitino Phenomenology
We construct the low-energy effective lagrangian for a light gravitino
coupled to the minimal supersymmetric standard model under the assumption that
supersymmetry breaking is communicated to the observable sector dominantly
through soft terms. Our effective lagrangian is written in terms of the
spin-1/2 Goldstino (the longitudinal component of the gravitino) transforming
under a non-linear realization of supersymmetry. In this lagrangian, the
Goldstino is derivatively coupled and all couplings of the Goldstino to light
fields are determined uniquely by the supersymmetry-breaking scale \sqrt{F}.
This lagrangian is therefore a useful starting point for further investigation
of the light gravitino in gauge-mediated supersymmetry breaking models. We show
that the invisible width of the Z into Goldstinos gives the constraint \sqrt{F}
> 140 GeV.Comment: 15 pages, LaTeX2e, 1 eps figure. Removed erroneous claim of coupling
of photon to gravitino to photons at order M^2 E^2 / F^2. Strongest bound is
from invisible Z width, giving F > (140 GeV)^
Análisis jurídico del código orgánico administrativo ecuatoriano y el código de procedimiento administrativo y de lo contencioso administrativo colombiano, a la luz de los principios constitucionales y el rol de la administración pública
Los autores aplican en este texto? la técnica de Derecho comparado entre Ecuador y Colombia, respecto a la legislación en materia administrativa y su relación con los textos constitucionales de ambos países. A partir de allí pretenden efectuar un análisis jurídico sobre el Código Orgánico Administrativo (en adelante COA) y el Estatuto de Régimen Jurídico Administrativo de la Función Ejecutiva (en adelante ERJAFE), determinando los fundamentos constitucionales que motivaron al Poder legislativo a expedir el COA, efectuando una comparación sobre ambos marcos normativos a la interpretación de los principios constitucionales
Precision Electroweak Data and Unification of Couplings in Warped Extra Dimensions
Warped extra dimensions allow a novel way of solving the hierarchy problem,
with all fundamental mass parameters of the theory naturally of the order of
the Planck scale. The observable value of the Higgs vacuum expectation value is
red-shifted, due to the localization of the Higgs field in the extra dimension.
It has been recently observed that, when the gauge fields propagate in the
bulk, unification of the gauge couplings may be achieved. Moreover, the
propagation of fermions in the bulk allows for a simple solution to potentially
dangerous proton decay problems. However, bulk gauge fields and fermions pose a
phenomenological challenge, since they tend to induce large corrections to the
precision electroweak observables. In this article, we study in detail the
effect of gauge and fermion fields propagating in the bulk in the presence of
gauge brane kinetic terms compatible with gauge coupling unification, and we
present ways of obtaining a consistent description of experimental data, while
allowing values of the first Kaluza Klein mode masses of the order of a few
TeV.Comment: 32 pages, 7 figures. References adde
Bulk Gauge Fields in Warped Space and Localized Supersymmetry Breaking
We consider five dimensional supersymmetric warped scenarios in which the
Standard Model quark and lepton fields are localized on the ultraviolet brane,
while the Standard Model gauge fields propagate in the bulk. Supersymmetry is
assumed to be broken on the infrared brane. The relative sizes of supersymmetry
breaking effects are found to depend on the hierarchy between the infrared
scale and the weak scale. If the infrared scale is much larger than the weak
scale the leading supersymmetry breaking effect on the visible brane is given
by gaugino mediation. The gaugino masses at the weak scale are proportional to
the square of the corresponding gauge coupling, while the dominant contribution
to the scalar masses arises from logarithmically enhanced radiative effects
involving the gaugino mass that are cutoff at the infrared scale. While the LSP
is the gravitino, the NLSP which is the stau is stable on collider time scales.
If however the infrared scale is close to the weak scale then the effects of
hard supersymmetry breaking operators on the scalar masses can become
comparable to those from gaugino mediation. These operators alter the relative
strengths of the couplings of gauge bosons and gauginos to matter, and give
loop contributions to the scalar masses that are also cutoff at the infrared
scale. The gaugino masses, while exhibiting a more complicated dependence on
the corresponding gauge coupling, remain hierarchical and become proportional
to the corresponding gauge coupling in the limit of strong supersymmetry
breaking. The scalar masses are finite and a loop factor smaller than the
gaugino masses. The LSP remains the gravitino.Comment: 36 pages, 2 figure
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