arXiv subjects
Publications and source records attributed to T. Barakat.
The magnetic moments of heavy sextet $J^P = {1\over 2}^+$ baryons are calculated in framework of the light cone QCD sum rules method. Linearly independent relations among the magnetic moments of these baryons are obtained. The results for the magnetic moments of heavy baryons obtained in this work are compared with the predictions of the other approaches.
Linear and nonlinear optical absorption coefficients of the two-dimensional semiconductor ring in the perpendicular magnetic field $\bf B$ are calculated within independent electron approximation. Characteristic feature of the energy spectrum are crossings of the levels with adjacent nonpositive magnetic quantum numbers as the intensity $B$ changes. It is shown that the absorption coefficient of the associated optical transition is drastically decreased at the fields corresponding to the crossing. Proposed model of the Volcano disc allows to get simple mathematical analytical results, which provide clear physical interpretation. An interplay between positive linear and intensity-dependent negative cubic absorption coefficients is discussed; in particular, critical light intensity at which additional resonances appear in the total absorption dependence on the light frequency, is calculated as a function of the magnetic field and levels' broadening.
The scale invariant of the effective potential of the standard model at two-loop is used as a boundary condition under the assumption that the two-loop effective potential approximates the full effective potential. This condition leads with the help of the renormalization group functions of the model at two-loop to an algebraic equation of the scalar self coupling with coefficients that depend on the gauge and the top quark couplings. It admits only two real positive solutions. One of them, in the absence of the gauge and top quark couplings, corresponds to the non-perturbative ultraviolet fixed point of the scalar renormalization group function and the other corresponds to the perturbative infrared fixed point. The dependence of the scalar coupling on the top quark and the strong couplings at two-loop radiative corrections is analyzed.
The perturbation technique within the framework of the asymptotic iteration method is used to obtain large-order shifted 1/N expansions, where N is the number of spatial dimensions. This method is contrary to the usual Rayleigh-Schrödinger perturbation theory, no matrix elements need to be calculated. The method is applied to the Schrödinger equation and the non-polynomial potential $V(r)=r^2+\frac{b r^2}{(1+cr^2)}$ in three dimensions is discussed as an illustrative example.
Exact solutions for vibrational levels of diatomic molecules via the Morse potential are obtained by means of the asymptotic iteration method. It is shown that, the numerical results for the energy eigenvalues of $^{7}Li_{2}$ are all in excellent agreement with the ones obtained before. Without any loss of generality, other states and molecules could be treated in a similar way.
The asymptotic iteration method is applied, to calculate the angular spheroidal eigenvalues $λ^{m}_{\ell}(c)$ with arbitrary complex size parameter $c$. It is shown that, the obtained numerical results of $λ^{m}_{\ell}(c)$ are all in excellent agreement with the available published data over the full range of parameter values $\ell$, $m$, and $c$. Some representative values of $λ^{m}_{\ell}(c)$ for large real $c$ are also given.
The rare $B\to K^{*}ν\barν$ decay when $K^{*}$ meson is longitudinally or transversely polarized is analysed in the context of the fourth generation model. A significant enhancement to the missing energy spectrum over the SM is recorded.
We study Dick quark-antiquark potential (up to a color factor) $V_D(r)={-α_s \over r} + gf \sqrt{N_c \over {2(N_c-1)}} \ln[exp(2mr)-1]$ in the heavy meson sector. This potential emerges from an effective dilaton-gluon coupling inspired from string theory and proves to be linearly rising at large distances which ensures quark confinement. The semi-relativistic wave equation which appears in the theory of relativistic quark-antiquark bound states is used. This equation is cast into a constituent second order Schrödinger-like equation with the inclusion of relativistic corrections up to order $(v/c)^{2}$ in the quark speeds. The resulting equation is solved for Dick potential via the Shifted-$l$ expansion technique (SLET). The obtained results show that the spin-averaged energy levels of heavy-mesons are well explained and agree with other potential models or QCD sum rules predictions. Moreover, as a by-product, our analysis assign to the dilaton a mass around 56.9 MeV lying within the range of many theoretical scenario of dilatonic mass.
The radiative leptonic $B_{c}\toτ\bar{ν_τ}γ$ decay is analysed in context of 2HDM. It is shown that with large values of $tanβ$, the contributions of Model II to the decay rate exceeds considerably the Standard Model ones, while the contributions of Model I overlap with the Standard Model predictions.
The semi-relativistic equation is cast into a second-order Schrodinger-like equation with the inclusion of relativistic corrections up to order (v/c)^2. The resulting equation is solved via the shifted-l expansion technique, which has been recently developed to get eigenvalues of relativistic and non-relativistic wave equations. The Coulomb, Oscillator, and the Coulomb-plus-linear potential used in qq-bar phenomenology are tested. The method gives quite accurate results over a wide range of r and any choice of quantum numbers n and l. However, a comparison of the present work with those of Lucha et al. and Nickisch et al. will serve as a test of this approach.