New Research in Physics

Abstract In this paper, to solve the current ambiguity in the entrance channels or of resonance state for Kaon-proton interaction at 4.2 Gev/c, a mixture of transition matrix elements for entrance channels of and in the resonance formation of have been used. A comparison of the theoretical invariant mass spectra with the totally Hemingway’s experimental data indicates that in this interaction, the channel is the dominant entrance channel. In the following, using the analysis method, the mass and width of the resonant state are respectively obtained and that are in a good agreement with the present values of mass and width of the in particle data group (PDG).

Abstract In this paper, quantum two-stream and multi-stream instabilities have been studied by taking into account the effect of Fermi pressure term. The dispersion relation is calculated by means of a quantum non-relativistic hydrodynamic model. It is shown that there is no any free energy for velocities shorter than Fermi velocity in the system and hence the plasma system is stable in this condition. On the other hand, it has been observed, taking into account the effect of Fermi pressure decreases the maximum growth rate of instabilities but cut-off wave number increases. It is found that the growth rate and cut-off wave number of two-stream instability is larger than multi-stream instability due to Focusing of energy.

Abstract In this paper we investigate self-focusing and intensity of Gaussian laser beam propagating through the homogeneous plasma in the external tapered magnetic field. It is known that the nonlinearities effects can be acquire by the laser-plasma interaction which can lead to the self-focusing of the laser beam. By considering these nonlinear effects, equation of beamwidth of Gaussian laser beam under the paraxial approximation has been obtained and numerically solved. Results of numerical method show that external tapered magnetic field can further boost the self-focusing and localize the beam intensity. Besides, effects of cyclotron frequency, plasma density and slope constant of magnetic field parameters on self-focusing have been investigated. In addition, more results on evaluation of laser beam intensity depict that in presence of tapered magnetic field and also by increasing the slope constant parameter of the tapered magnetic field, the intensity of laser beam increases noticeably.

Abstract In this paper, 3D simulation is used in the interaction of the Gaussian laser pulse with plasma electrons that have ramp density parameter in the nonlinear regime of the laser wake-field acceleration (LWFA). The influence of the ramp electrons density parameter on acceleration of the bunch electrons and percent of the trap of electrons at the end of the bubble is investigated. The effect of the density ramp environment as a way of the increase in the deceleration length numerically and eventually the influence of the initial energy and direction of the bunch electrons is proved. By determining the optimum plasma density ramp, the percentage of trapping and spontaneous injection of electrons will increase substantially.

Abstract Liver cancer is one of the most common leading causes of cancer death worldwide. Radio frequency ablation (RFA) is one of the best ways to treat liver cancer. It is very noticeable and surprising. The success of the treatment depends on choosing an appropriate condition for it. In the paper, the treatment of liver tumor by a needle electrode is studied theoretically. The liver tissue is considered as a cylinder with 120 mm in height and 50 mm in radius. The simulations are performed by solving Bioheat equation with considering the RF energy absorption in the tissue and tumor, the boundary and primary conditions. The modeling is done by the finite element method (FEM). Also, the effect of blood perfusion and the vessel are included in this study. The results at 10 minutes and electrical potential of 18 V show that an elliptical cancerous tumor with the large-diameter of 27 mm and the short-diameter of 9 mm is damaged completely. According the simulations, the needle RF electrode is suitable for the treatment of various dimensions, deep and metastatic cancerous tumors. Also, size, shape, and elongation of elliptical cancerous tumors which can be destroyed by using different electrical potentials, are estimated in the paper. The results show that increasing the electrical potential leads to the reduction of the elliptical elongation and the coagulation area will be closer to the sphere.

Abstract The Generalized Parton Distributions (GPDs) in the proton is calculated for the u and d valence quarks, using the so-called "valon" representation of hadrons. We have used the existing experimental data on Dirac form factor and determined the free parameter of the model. Existing data agree with our theoretical calculations. Our model results are also compared with some other models.