151 research outputs found
The 125 GeV boson: A composite scalar?
Assuming that the 125 GeV particle observed at the LHC is a composite scalar
and responsible for the electroweak gauge symmetry breaking, we consider the
possibility that the bound state is generated by a non-Abelian gauge theory
with dynamically generated gauge boson masses and a specific chiral symmetry
breaking dynamics motivated by confinement. The scalar mass is computed with
the use of the Bethe-Salpeter equation and its normalization condition as a
function of the SU(N) group and the respective fermionic representation. If the
fermions that form the composite state are in the fundamental representation of
the SU(N) group, we can generate such light boson only for one specific number
of fermions for each group. In the case of small groups, like SU(2) to SU(5),
and two fermions in the adjoint representation we find that is quite improbable
to generate such light composite scalar.Comment: 24 pages, 5 figures, discussion extended, references added; version
to appear in Phys. Rev.
Spontaneous CP violation in the 3-3-1 model with right-handed neutrinos
We implement the mechanism of spontaneous CP violation in the 3-3-1 model
with right-handed neutrinos and recognize their sources of CP violation. Our
main result is that the mechanism works already in the minimal version of the
model and new sources of CP violation emerges as an effect of new physics at
energies higher than the electroweak scale.Comment: Major changes in the quark sector, electronic dipole moment of the
neutron was evaluated, accepted for publication in the physical review
Family Dependence in SU(3)_C X SU(3)_L X U(1)_X models
Using experimental results at the Z-pole and atomic parity violation, we
perform a chi-squared fit at 95% CL to obtain family-dependent bounds to Z_2
mass and Z-Z' mixing angle in the framework of SU(3)_C X SU(3)_L X U(1)_X
models. The allowed regions depend on the assignment of the quark families in
mass eigenstates into the three different families in weak eigenstates that
cancel anomaliesComment: 14 pages, 2 figures, LaTeX2e; added references, added equations with
electroweak corrections for section 4. Version to appear in Phys. Rev.
Light composite Higgs boson from the normalized Bethe-Salpeter equation
Scalar composite boson masses have been computed in QCD and Technicolor
theories with the help of the homogeneous Bethe-Salpeter equation (BSE),
resulting in a scalar mass that is twice the dynamically generated fermion or
technifermion mass (). We show that in the case of walking (or
quasi-conformal) technicolor theories, where the behavior with the
momenta may be quite different from the one predicted by the standard operator
product expansion, this result is incomplete and we must consider the effect of
the normalization condition of the BSE to determine the scalar masses. We
compute the composite Higgs boson mass for several groups with technifermions
in the fundamental and higher dimensional representations and comment about the
experimental constraints on these theories, which indicate that models based on
walking theories with fermions in the fundamental representation may, within
the limitations of our approach, have masses quite near the actual direct
exclusion limit.Comment: 9 pages, 4 figures, minor corrections, to appear in Physical Review
Neutrino Decay and Neutrinoless Double Beta Decay in a 3-3-1 Model
In this work we show that the implementation of spontaneous breaking of the
lepton number in the 3-3-1 model with right-handed neutrinos gives rise to fast
neutrino decay with majoron emission and generates a bunch of new contributions
to the neutrinoless double beta decay.Comment: Version accepted for publication in the Phys. Rev.
Quantization of eletric charge, the neutrino and generation nonuniversality
text of abstract It is showed that the eletric charge quantization is
unconnected to Majorana neutrino in the non-universal generations
leptoquark-bilepton flavordynamics which includes the right-handed neutrino and
an explicit U(1) factor in the gauge semisimple group.Comment: 4 pages, latex ps, no figure
Limit on the fermion masses in technicolor models
Recently it has been pointed out that no limits can be put on the scale of
fermion mass generation in technicolor models, because the relation
between the fermion masses and depends on the dimensionality of the
interaction responsible for generating the fermion mass. Depending on this
dimensionality it may happens that does not depend on at all. We show
that exactly in this case may reach its largest value, which is almost
saturated by the top quark mass. We make few comments on the question of how
large can be a dynamically generated fermion mass.Comment: 5 pages, 1 figure, RevTeX
Outcomes After Bidirectional Cavopulmonary Shunt in Infants Less Than 6 Months Old
AbstractObjectives. We sought to assess the results after bidirectional cavopulmonary shunt (BCPS) in infants <6 months old and to identify risk factors for poor outcome.Background. Although BCPS is a well established procedure for the palliation of patients with a single-ventricle heart, there have been very few reports of outcomes after BCPS in young infants.Methods. Since 1990, 42 infants between 0.8 and 6.0 months of age (mean [±SD] 3.7 ± 1.4) have undergone BCPS for primary (n = 16) or secondary (n = 26) palliation of tricuspid atresia (n = 13), hypoplastic left heart syndrome (n = 10) or other forms of functional single-ventricle heart (n = 19). Accessory pulmonary blood flow was included in 18 patients. Preoperative and perioperative data were gathered on retrospective review of patient records, and follow-up was conducted by means of direct physician contact or record review.Results. The overall hospital mortality rate, including that associated with reoperations, was 4.8% (2 of 42 patients). Seven patients (17%) required reoperation related to the BCPS or pulmonary blood flow in the early postoperative period: Procedures included take-down of the BCPS in four patients, with one early death, and procedures to decrease pulmonary blood flow in three patients. Age <1 month correlated significantly with early death and with early failure of the BCPS (death or take-down). Follow-up of the 37 patients discharged with intact BCPS was obtained at a mean ± SD of 14.3 ± 11.3 months postoperatively, during which time three patients died (at 6.5 ± 2.5 months). The 2-year actuarial survival rate for patients undergoing BCPS at <6 months of age was 86%. Overall freedom from death or take-down (including early and late events) was significantly lower in patients <2 months old than in those >2 months old. Four patients have undergone successful Fontan completion (18.3 ± 2.9 months postoperatively), and one patient whose BCPS was taken down subsequently underwent successful restoration of a BCPS.Conclusions. Outcomes after BCPS in young infants are comparable to those in older infants and children. However, our current preference is to defer this procedure until after 2 months of age.(J Am Coll Cardiol 1997;29:1365–70
Higgs phenomenology of supersymmetric economical 3-3-1 model
We explore the Higgs sector in the supersymmetric economical 3-3-1 model and
find new features in this sector. The charged Higgs sector is revised i.e., in
difference of the previous work, the exact eigenvalues and states are obtained
without any approximation. In this model, there are three Higgs bosons having
masses equal to that of the gauge bosons--the W and extra X and Y. There is one
scalar boson with mass of 91.4 GeV, which is closed to the boson mass and
in good agreement with present limit: 89.8 GeV at 95% CL. The condition of
eliminating for charged scalar tachyon leads to splitting of VEV at the first
symmetry breaking, namely, . The interactions among the
standard model gauge bosons and scalar fields in the framework of the
supersymmetric economical 3-3-1 model are presented. From these couplings, at
some limit, almost scalar Higgs fields can be recognized in accordance with the
standard model. The hadronic cross section for production of the bilepton
charged Higgs boson at the CERN LHC in the effective vector boson approximation
is calculated. Numerical evaluation shows that the cross section can exceed
35.8 fb.Comment: 33 pages, 1 figur
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