318 research outputs found
Models of Yukawa interaction in the two Higgs doublet model, and their collider phenomenology
Possible models of Yukawa interaction are discussed in the two Higgs doublet
model (THDM) under the discrete symmetry imposed to avoid the flavor changing
neutral current at the leading order. It is known that there are four types of
such models corresponding to the possible different assignment of charges for
the discrete symmetry on quarks and leptons. We first examine decay properties
of Higgs bosons in each type of the models, and summarize constraints on the
models from current experimental data. We then shed light on the differences
among these models in collider phenomenology. In particular, we mainly discuss
so-called the Type-II THDM and the Type-X THDM. The Type-II THDM corresponds to
the model with the same Yukawa interaction as the minimal supersymmetric
standard model (MSSM). On the other hand, in the Type-X THDM, additional Higgs
bosons can predominantly decay into leptons. This scenario may be interesting
because of the motivation for a light charged Higgs boson scenario such as in
the TeV scale model of neutrino, dark matter and baryogenesis. We study how we
can distinguish the Type-X THDM from the MSSM at the Large Hadron Collider and
the International Linear Collider.Comment: 33 pages, 41 eps files, version accepted for publication in Physical
Review
Electromagnetic Structure of the Meson in the Light-Front Quark Model
We investigate the elastic form factors of the rho meson in the light-front
quark model(LFQM). With the phenomenologically accessible meson vertices
including the one obtained by the Melosh transformation frequently used in the
LFQM, we find that only the helicity matrix element of the plus
current receives the zero-mode contribution. We quantify the zero-mode
contribution in the helicity amplitude using the angular condition of
spin-1 system. After taking care of the zero-mode issue, we obtain the
magnetic() and quadrupole() moments of the rho meson as and
, respectively, in the LFQM consistent with the Melosh transformation
and compare our results with other available theoretical predictions.Comment: 14pages, 5figure
Photon distribution amplitudes and light-cone wave functions in chiral quark models
The leading- and higher-twist distribution amplitudes and light-cone wave
functions of real and virtual photons are analyzed in chiral quark models. The
calculations are performed in the nonlocal quark model based on the instanton
picture of QCD vacuum, as well as in the spectral quark model and the
Nambu--Jona-Lasinio model with the Pauli-Villars regulator, which both treat
interaction of quarks with external fields locally. We find that in all
considered models the leading-twist distribution amplitudes of the real photon
defined at the quark-model momentum scale are constant or remarkably close to
the constant in the variable, thus are far from the asymptotic limit form.
The QCD evolution to higher momentum scales is necessary and we carry it out at
the leading order of the perturbative theory for the leading-twist amplitudes.
We provide estimates for the magnetic susceptibility of the quark condensate
and the coupling , which in the nonlocal model turn out
to be close to the estimates from QCD sum rules. We find the higher-twist
distribution amplitudes at the quark model scale and compare them to the
Wandzura-Wilczek estimates. In addition, in the spectral model we evaluate the
distribution amplitudes and light-cone wave functions of the -meson.Comment: 24 pages, 15 figure
Preparation and structural stability of ordered nanocomposites: opal matrix - lead titanates
The conditions for the formation of nanocomposites based on the basis of lattice packings of SiO[2] nanospheres (opal matrices) with included crystallites of lead titanates (PbTiO[3] and PbTi[3]O[7]) in interspherical nanospacing are considered. For the formation of nanocomposites are used sample opal matrices with dimensions of single-domain regions >=0,1 mm.{3} The diameter of SiO[2] nanospheres was ~260 nm. Obtained nanocomposites volume >2 cm{3} in filling >20% of interspherical nanospacing PbTiO[3], PbTi[3]O[7] crystallites were size of 16-36 nm. Using X-ray diffraction and Raman spectroscopy are studied composition and structural stability when heated nanocomposites to 550°C, which allowed the identification of a local phase transition with change of the space group. The dependence of the composition of synthesized materials on the conditions of their preparation is submitted
Scalar Particle Contribution to Higgs Production via Gluon Fusion at NLO
We consider the gluon fusion production cross section of a scalar Higgs boson
in models where fermion and scalar massive colored particles are present. We
report analytic expressions for the matrix elements of , , and processes completing the calculation of the NLO QCD
corrections in these extended scenarios. The formulas are written in a complete
general case, allowing a flexible use for different theoretical models.
Applications of our results to two different models are presented: i) a model
in which the SM Higgs sector is augmented by a weak doublet scalar in the
adjoint representation. ii) The MSSM, in the limit of neglecting the
gluino contribution to the cross section.Comment: 20 pages, 5 figures. Minor changes. Refs. adde
Assessment of the quality of life of patients with achalasia of the cardia after videoendoscopic Heller cardiomyotomy with Dor fundoplication
Background. The leading symptom of achalasia of cardia (AC) is dysphagia, along with other symptoms significantly affecting the quality of life of patients.The aim. Based on the results of questioning patients using special and general questionnaires and using special methods for studying the closing function of the cardia, to evaluate the quality of life of patients with stages 2–4 of AC after video-laparoscopic esophagocardiomyotomy according to Heller with anterior hemiasophagofundoplication according to Dor.Materials and methods. The basis of the work was the analysis of the results of esophagocardiomyotomy according to Heller with anterior hemiesophagofundoplication according to Dor in 106 patients with stages 2–4 of AC. The postoperative follow-up period averaged 2 ± 0.4 years. In the pre- and postoperative periods, the results of fluoroscopy of the esophagus and stomach, manometry of the esophagus and the esophageal-gastric junction were studied, and three questionnaires were used (Eckhardt scale, GIQLI questionnaire and SF-36).Results. Analysis of the data obtained showed that the clinical manifestations of the disease in the postoperative period decreased in all patients with stages 2–4 of AC, the results in patients with stage 2 were better than in patients with stages 3 and 4 (p < 0.05). The results of fluoroscopy of the esophagus and stomach, manometry of the esophagus and the esophagogastric junction showed improvement in the postoperative period in patients at all stages of the disease, the results of patients with stage 4 were worse compared with stages 2 and 3 (p < 0.05).Conclusion. Videoendoscopic esophagomyotomy according to Heller with anterior fundoplication according to Dor significantly reduces the severity of clinical manifestations of AC and improves the quality of life in patients with stages 2–4 of AC, as a result of which surgery should be recommended to patients already at stage 2 and organ-preserving surgery at stage 4 of the disease
First Measurement of Target And Double Spin Asymmetries for ep → epπ° in the Nucleon Resonance Region Above the Δ (1232)
The exclusive channel polarized proton(polarized e,e\u27 p)π0 was studied in the first and second nucleon resonance regions in the Q2 range from 0.187 to 0.770 GeV2 at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the π0 and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region. This data set, once included in the global fits of the above models, is expected to place strong constraints on the electrocoupling amplitudes A 1/2 and S 1/2 for the Roper resonance N (1400) P11, and the N(1535)S11 and N(1520)D13 states
Electron Scattering from High-Momentum Neutrons in Deuterium
We report results from an experiment measuring the semiinclusive reaction 2H(e,e′ps) in which the proton ps is moving at a large angle relative to the momentum transfer. If we assume that the proton was a spectator to the reaction taking place on the neutron in deuterium, the initial state of that neutron can be inferred. This method, known as spectator tagging, can be used to study electron scattering from high-momentum (off-shell) neutrons in deuterium. The data were taken with a 5.765 GeV electron beam on a deuterium target in Jefferson Laboratory\u27s Hall B, using the CEBAF large acceptance spectrometer. A reduced cross section was extracted for different values of final state missing mass W∗, backward proton momentum →ps, and momentum transfer Q2. The data are compared to a simple plane wave impulse approximation (PWIA) spectator model. A strong enhancement in the data observed at transverse kinematics is not reproduced by the PWIA model. This enhancement can likely be associated with the contribution of final state interactions (FSI) that were not incorporated into the model. Within the framework of the simple spectator model, a “bound neutron structure function” Feff2n was extracted as a function of W∗ and the scaling variable x∗ at extreme backward kinematics, where the effects of FSI appear to be smaller. For ps \u3e 0.4 GeV/c, where the neutron is far off-shell, the model overestimates the value of Feff2n in the region of x∗ between 0.25 and 0.6. A dependence of the bound neutron structure function on the neutron\u27s “off-shell-ness” is one possible effect that can cause the observed deviation
Measurement of Direct fₒ(980) Photoproduction on the Proton
We report on the results of the first measurement of exclusive f0(980) meson photoproduction on protons for Eγ = 3.0–3.8 GeV and −t = 0.4–1.0 GeV2 . Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The resonance was detected via its decay in the π+π− channel by performing a partial wave analysis of the reaction γp→pπ+π− . Clear evidence of the f0(980) meson was found in the interference between P and S waves at M π+π− ∼1 GeV. The S -wave differential cross section integrated in the mass range of the f0(980) was found to be a factor of about 50 smaller than the cross section for the ρ meson. This is the first time the f0(980) meson has been measured in a photoproduction experiment
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