4,043 research outputs found
Phenomenological Comparison of Models with Extended Higgs Sectors
Beyond the Standard Model (SM) extensions usually include extended Higgs
sectors. Models with singlet or doublet fields are the simplest ones that are
compatible with the parameter constraint. The discovery of new non-SM
Higgs bosons and the identification of the underlying model requires dedicated
Higgs properties analyses. In this paper, we compare several Higgs sectors
featuring 3 CP-even neutral Higgs bosons that are also motivated by their
simplicity and their capability to solve some of the flaws of the SM. They are:
the SM extended by a complex singlet field (CxSM), the singlet extension of the
2-Higgs-Doublet Model (N2HDM), and the Next-to-Minimal Supersymmetric SM
extension (NMSSM). In addition, we analyse the CP-violating 2-Higgs-Doublet
Model (C2HDM), which provides 3 neutral Higgs bosons with a pseudoscalar
admixture. This allows us to compare the effects of singlet and pseudoscalar
admixtures. Through dedicated scans of the allowed parameter space of the
models, we analyse the phenomenologically viable scenarios from the view point
of the SM-like Higgs boson and of the signal rates of the non-SM-like Higgs
bosons to be found. In particular, we analyse the effect of
singlet/pseudoscalar admixture, and the potential to differentiate these models
in the near future. This is supported by a study of couplings sums of the Higgs
bosons to massive gauge bosons and to fermions, where we identify features that
allow us to distinguish the models, in particular when only part of the Higgs
spectrum is discovered. Our results can be taken as guidelines for future LHC
data analyses, by the ATLAS and CMS experiments, to identify specific benchmark
points aimed at revealing the underlying model.Comment: Matches journal version; figures for NMSSM changed; conclusions
unchange
One-loop conformal anomaly in an implicit momentum space regularization framework
In this paper we consider matter fields in a gravitational background in
order to compute the breaking of the conformal current at one-loop order.
Standard perturbative calculations of conformal symmetry breaking expressed by
the non-zero trace of the energy-momentum tensor have shown that some violating
terms are regularization dependent, which may suggest the existence of spurious
breaking terms in the anomaly. Therefore, we perform the calculation in a
momentum space regularization framework in which regularization dependent terms
are judiciously parametrized. We compare our results with those obtained in the
literature and conclude that there is an unavoidable arbitrariness in the
anomalous term .Comment: in European Physical Journal C, 201
Hubbard-model description of the high-energy spin-spectral-weight distribution in La(2)CuO(4)
The spectral-weight distribution in recent neutron scattering experiments on
the parent compound LaCuO (LCO), which are limited in energy range to
about 450\,meV, is studied in the framework of the Hubbard model on the square
lattice with effective nearest-neighbor transfer integral and on-site
repulsion . Our study combines a number of numerical and theoretical
approaches, including, in addition to standard treatments, density matrix
renormalization group calculations for Hubbard cylinders and a suitable spinon
approach for the spin excitations. Our results confirm that the
magnitude suitable to LCO corresponds to intermediate values smaller than
the bandwidth , which we estimate to be eV for
. This confirms the unsuitability of the conventional linear
spin-wave theory. Our theoretical studies provide evidence for the occurrence
of ground-state d-wave spinon pairing in the half-filled Hubbard model on the
square lattice. This pairing applies only to the rotated-electron spin degrees
of freedom, but it could play a role in a possible electron d-wave pairing
formation upon hole doping. We find that the higher-energy spin spectral weight
extends to about 566 meV and is located at and near the momentum .
The continuum weight energy-integrated intensity vanishes or is extremely small
at momentum . This behavior of this intensity is consistent with that
of the spin waves observed in recent high-energy neutron scattering
experiments, which are damped at the momentum . We suggest that future
LCO neutron scattering experiments scan the energies between 450 meV and 566
meV and momenta around .Comment: 23 pages, 5 figure
Improved estimate of electron capture rates on nuclei during stellar core collapse
Electron captures on nuclei play an important role in the dynamics of the
collapsing core of a massive star that leads to a supernova explosion. Recent
calculations of these capture rates were based on microscopic models which
account for relevant degrees of freedom. Due to computational restrictions such
calculations were limited to a modest number of nuclei, mainly in the mass
range A=45-110. Recent supernova simulations show that this pool of nuclei,
however, omits the very neutron-rich and heavy nuclei which dominate the
nuclear composition during the last phase of the collapse before neutrino
trapping. Assuming that the composition is given by Nuclear Statistical
Equilibrium we present here electron capture rates for collapse conditions
derived from individual rates for roughly 2700 individual nuclei. For those
nuclei which dominate in the early stage of the collapse, the individual rates
are derived within the framework of microscopic models, while for the nuclei
which dominate at high densities we have derived the rates based on the Random
Phase Approximation with a global parametrization of the single particle
occupation numbers. In addition, we have improved previous rate evaluations by
properly including screening corrections to the reaction rates into account.Comment: 32 pages, 13 figures, 1 table; elsart; to appear in Nuclear Physics
Urachal Tumor: A Case Report of an Extremely Rare Carcinoma
The urachus is a tubular structure that connects the bladder to the allantois in the embryonic development, involuting after the third trimester. The urachus carcinoma is an extremely rare tumor that accounts for <1% of all bladder cancers. We report a case of a 46-year-old woman, with no past medical history, complaining of hematuria with 6-month duration and a physical exam and an abdominal computed topographic scan revealing an exophytic mass of 6.8 cm longer axis that grew depending on the anterior bladder wall, invading the anterior abdominal wall. Cystoscopy detected mucosal erosion. The biopsy showed structures of adenocarcinoma of enteric type. The surgical specimen showed urachus adenocarcinoma of enteric type with stage IVA in the Sheldon system and stage III in the Mayo system. This case has a 3-year follow-up without disease recurrence.info:eu-repo/semantics/publishedVersio
Enzymatic production of fructose fatty acid ester using lipases from C. antarctica and porcine pancreatic
The aim of this work was to produce fructose fatty acid ester by enzymatic esterification of a fatty
acid (oleic acid or linoleic acid) with fructose, using lipases (CALB) from Candida antarctica type B
and porcine pancreas. The esterification reaction was conducted at 150 rpm and 40 °C during 72
hours. Equimolar (0.5 mmol) amounts of fructose and fatty acid were mixed with 0.6 ml of
ethanol and sodium sulfate anhydrous (0.1 g) was added for the adsorption of the water
generated during the reaction. In all experiments, 22.5 mg of lipase were used. A control
experiment was performed using the same conditions except for the addition of lipase. Samples
were analyzed by thin layer chromatography (TLC), using silica gel plates. The plates were placed
in an iodine chamber to develop fatty acid and sugar ester spots. According to the literature an Rf
of 0.5 is expected for the fructose fatty acid ester using chloroform/ hexane (1:1, v/ v) as eluting
solvent. Four different reaction schemes were studied in this work namely, sample 1 (oleic acid,
fructose, C. antarctica lipase, sodium sulfate and ethanol), sample 2 (oleic acid, fructose, porcine
pancreatic lipase, sodium sulfate and ethanol), sample 3 (linoleic acid, fructose, C. antarctica
lipase, sodium sulfate and ethanol) and sample 4 (linoleic acid, fructose, porcine pancreatic
lipase, sodium sulfate and ethanol). From the TLC assays, the formation of fructose ester was
observed for samples 1, 2 and 3. Additionally, the yield of esterification was determined by
calculating the amount of residual fatty acid in the reaction mixture, which was determined using
a volumetric method, as described elsewhere. Esterification yields of 74.3, 41.4, 63.5 and 11.2 %
(v/ v) were determined for samples 1 to 4, respectively. Therefore, it was possible to conclude
that the lipase obtained from C. antarctica had a better performance than the one obtained from
porcine pancreas. Furthermore, the reaction schemes that used oleic acid conducted to higher
yields of fructose ester production. These results point out that the enzymatic production of
fructose esters is worthwhile and suggest the need for further research
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