arXiv subjects

H. Abbasi

Publications and source records attributed to H. Abbasi.

5 recordsLinked to original sources

arXiv2015

Polarized and Unpolarized Lepton Pair Forward-backward Asymmetries in $\overline{B}\rightarrow \overline{K}_{0}^{*}(1430) \ell^+\ell^-$ and $\overline{B}\rightarrow \overline{K} \ell^+\ell^-$ Decays in Two Higgs Doublet Model

In this paper we shall focus on the effects of concrete models such as SM and Model III of 2HDM on the polarized and unpolarized forward-backward asymmetries of $\overline{B}\rightarrow \overline{K}_0^{*}(1430) \ell^+\ell^-$ and $\overline{B}\rightarrow \overline{K} \ell^+\ell^-$ decays. The obtained results of these decay modes are compared to each other. Also, we obtain the minimum required number of events for detecting each asymmetry and compare them with the number of produced $B\bar{B}$ pairs at the LHC or supposed to be produced at the Super-LHC. At the end, we conclude that the study of these asymmetries for $\overline{B}\rightarrow \overline{K}_0^*(1430) \ell^+\ell^-$ and $\overline{B}\rightarrow \overline{K} \ell^+\ell^-$ processes are very effective tools for establishing new physics in the future B-physics experiments.

hep-ph↗

arXiv2015

Hybrid (kinetic-fluid) simulation scheme based on method of characteristics

Certain features of the method of characteristics are of considerable interest in relation with Vlasov simulation [H. Abbasi {\it et al}, Phys. Rev. E \textbf{84}, 036702 (2011)]. A Vlasov simulation scheme of this kind can be recurrence free providing initial phase points in velocity space are set randomly. Naturally, less filtering of fine-structures (arising from grid spacing) is possible as there is now a smaller scale than the grid spacing that is average distance between two phase points. Its interpolation scheme is very simple in form and carried out with less operations. In our previous report, the simplest model (immobile ions) was considered to merely demonstrate the important features. Now, a hybrid model is introduced that solves the coupled Vlasov-Fluid-Poisson system self-consistently. A possible application of the code is the study of ion-acoustic (IA) soliton attributes. To this end, a collisionless plasma with hot electrons and cold positive ions is considered. For electrons, the collisionless Vlasov equation is solved by following collisionless phase point trajectories in phase space while ions obey the fluid equations. The periodic boundary conditions are assumed. Both, the characteristic equations of the Vlasov equation and the fluid equations are solved using the Leapfrog-Trapezoidal method. However, to obtain the first half-time step of the Leapfrog, the Euler-Trapezoidal scheme, is employed. The presented scheme conveniently couples the two well-known grids in the Leapfrog method. The first test of the model is an stationary IA soliton. Trapping of electrons is considered and the associated phase space hole is shown. Then as a non-stationary test, the IA soliton generation from a localized initial profile is examined. Conservation laws are the other benchmark tests.

physics.plasm-ph↗

arXiv2010

Vlasov model using kinetic phase point trajectories

A method of solution of the collisionless Vlasov equation, by following collisionless phase point trajectories in phase space, is presented. It is shown that by increasing the number of phase points, without enhancing the resolution of phase space grid, the accuracy of simulation will be improved. Besides, the phase points spacing introduces a smaller scale than grid spacing on which fine structures might be more conveniently handled. In order to perform simulation with a large population of phase points, an effective interpolation scheme is introduced that reduces the number of operations. It is shown that by randomizing initial position of the phase points along velocity axis, the recurrence effect does not happen. Finally, the standard problem of linear Landau damping will be examined.

physics.plasm-ph↗

arXiv2005

Subsonic ion-acoustic solitons

In this paper, the nonlinear theory of plasma waves is extended to the plasmas that their equilibrium state are specified by the non-Maxwellian (here kappa) distribution. We believe that the extension is very important since most of the space and some of laboratory plasmas are not in the Maxwellian equilibrium. Although the linear theory of this issue has been known for the decades but, to our knowledge, this is the first attempt in opening the gate to the nonlinear world of plasma waves with the non-Maxwellian equilibrium. As an example the ion-acoustic solitons are studied in this framework taking into account the electron trapping in the trough of longitudinal field. It is shown, as the most important result regarding to the non-Maxwillian equilibrium, that there is the possibility for the ion-acoustic solitons to move subsonically. The solitons velocity and their width are monotonically increasing functions of spectral index ($κ$) and approach to the their Maxwellian values as $κ\to \infty$.

physics.plasm-ph↗

arXiv2005

A Computational Fluid Model for Investigation of Plasma Waves and Instabilities

A computational fluid model is developed to study waves and instabilities. A new technique involving initial perturbations in configuration space have been implemented to excite the plasma waves; i.e. the perturbations acting similar to a random velocity distribution in particle in cell (PIC) codes. This forms a new powerful tool for investigation of many waves arising in both thermal and cold plasmas and as such will allow investigation of problems demanding scales and resolution not yet possible by PIC codes. The model predicts Langmuir waves, two stream instabilities, nonlinear wave-wave interaction, and the Debye screening effects. The agreement between theory and simulation where analytic results are available are excellent.

physics.plasm-ph↗