Sfermion masses in the supersymmetric economical 3-3-1 model

Sfermion masses and eigenstates in the supersymmetric economical 3-3-1 model are studied. By lepton number conservation, the exotic squarks and superpartners of ordinary quarks are decoupled. Due to the fact that in the 3-3-1 models, one generation of quarks behaves differently from other two, by R-parity conservation, the mass mixing matrix of the squarks in this model are smaller than that in the Minimal Supersymmetric Standard Model (MSSM). Assuming substantial mixing in pairs of highest flavours, we are able to get mass spectrum and eigenstates of all the sfermions. In the effective approximation, the slepton mass splittings in the first two generations, are consistent with those in the MSSM, namely: m^2_{\tilde{l}_L} - m^2_{\tilde{\nu}_{l L}} = m_W^2 \cos 2\ga $(l=e, \mu)$. In addition, within the above effective limit, there exists degeneracy among sneutrinos in each multiplet: $m^2_{\tilde{\nu}_{l L}} = m^2_{\tilde{\nu}_{l R}}$. In contradiction to the MSSM, the squark mass splittings are different for each generation and not to be m_W^2 \cos 2\ga.Comment: 34 pages, 2 figures, Revised version in which D-term and F-term contributions are slightly change

Supersymmetric economical 3-3-1 model

The supersymmetric extension of the economical 3-3-1 model is presented. The constraint equations and the gauge boson identification establish a relation between the vacuum expectation values (VEVs) at the top and bottom elements of the Higgs triplet $\chi$ and its supersymmetric counterpart $\chi^\prime$. Because of this relation, the exact diagonalization of neutral gauge boson sector has been performed. The gauge bosons and their associated Goldstone ones mix in the same way as in non-supersymmetric version. This is also correct in the case of gauginos. The eigenvalues and eigenstates in the Higgs sector are derived. The model contains a heavy neutral Higgs boson with mass equal to those of the neutral non-Hermitian gauge boson $X^0$ and a charged scalar with mass equal to those of the $W$ boson in the standard model, i. e. $m_{\varrho_1} = m_W$. This result is in good agreement with the present estimation: $m_{H^\pm} > 79.3$ GeV, CL= 95 %. We also show that the boson sector and the fermion sector gain masses in the same way as in the non-supersymmetric case.Comment: 33 page

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 $Z$ 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, $w \simeq w^\prime$. 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

Density functional theory calculations of the carbon ELNES of small diameter armchair and zigzag nanotubes: core-hole, curvature and momentum transfer orientation effects

We perform density functional theory calculations on a series of armchair and zigzag nanotubes of diameters less than 1nm using the all-electron Full-Potential(-Linearised)-Augmented-Plane-Wave (FPLAPW) method. Emphasis is laid on the effects of curvature, the electron beam orientation and the inclusion of the core-hole on the carbon electron energy loss K-edge. The electron energy loss near-edge spectra of all the studied tubes show strong curvature effects compared to that of flat graphene. The curvature induced $\pi-\sigma$ hybridisation is shown to have a more drastic effect on the electronic properties of zigzag tubes than on those of armchair tubes. We show that the core-hole effect must be accounted for in order to correctly reproduce electron energy loss measurements. We also find that, the energy loss near edge spectra of these carbon systems are dominantly dipole selected and that they can be expressed simply as a proportionality with the local momentum projected density of states, thus portraying the weak energy dependence of the transition matrix elements. Compared to graphite, the ELNES of carbon nanotubes show a reduced anisotropy.Comment: 25 pages, 15 figures, revtex4 submitted for publication to Phys. Rev.

MATERIALS AND INTERFACES CHARACTERIZATION BY MICRO-RAMAN SPECTROSCOPY

Several aspects of Raman and micro-Raman spectroscopy are shown and applied for the characterization of semiconductor materials and bi-layers of semiconductor on semiconductor and insulator on semiconductor. As a molecular technique, Raman spectroscopy will inform not only on the nature of elements but also on chemical bonds between atoms. Raman spectroscopy also permits the studies of disordered or amorphous materials. Based on the anisotropy in Raman scattering, the determination of the orientation of surfaces and thin layers becomes also easy. Micro-Raman spectroscopy, with a spatial resolution of the order of 1 µm2, allows the study of heterogenous or very small materials. This technique is very helpful in the determination of heterogeneity, stress and gradient in semiconductors. On step-etched or bevelled samples of a bi-layer, micro-Raman spectroscopy helps to examine the epitaxy quality of the deposit versus its thickness and also to detect eventual chemical bonds between deposit and substrate

Spectre Raman de résonance et fonction de l'énergie potentielle du bromure d'iode en solution

Le spectre Raman de résonance de IBr est enregistré dans divers solvants. Une progression de 17 harmoniques a pu être observée, ce qui permet le calcul, avec une bonne précision, des constantes spectroscopiques ωe et d'anharmonicité ωexe et ωeye, ainsi que la fonction de l'énergie potentielle de IBr en solution : V = [math] x 2 x 105q2 — 1,49 x 1013q3 + 1,55 x 1021q4 La diminution de l'anharmonicité de IBr en solution dans les solvants non ou peu polaires est interprétée par une contribution importante des forces répulsives entre soluté et solvant

Pesticide use in Vietnamese vegetable production : a 10-year study

Vietnam has had varying success over the past decade with its pesticides policy. Some of the most toxic pesticides have been banned from the market. But while many countries have successfully decreased agricultural pesticide use per hectare, this has not (yet) happened in Vietnam. Due to insufficient pesticide management capacity of the Vietnamese government, pesticide types and quantities registered and distributed on the market have substantially increased in Vietnam over the last 10 years. A 10-year monitoring programme at farm level showed that pesticide use follows the increasing pesticide availability on the market, and many toxic and illegal pesticides are still being used. In an agricultural country dominated by millions of small-scale farmers and with limited state capacity for control at farm level, reduction of the use of the most toxic pesticides can best be achieved by more effective pesticide market control through stricter and more effective state regulations and implementation, aimed at eliminating illegal, low quality and counterfeit pesticides from the market. But even then, better state and private extension services, and greater state capacity for control and enforcement remain essential in enabling farmers to make better decisions about pesticide use.</p