Mass Spectrum and Decay Constants of Heavy Quarkonia

In this paper, a non-relativistic potential model is used to find the solution of radial Schrodinger wave equation by using Crank Nicolson discretization for heavy quarkonia ( ̅, ̅). After solving the Schrodinger radial wave equation, the mass spectrum and hyperfine splitting of heavy quarkonia are calculated with and without relativistic corrections. The root means square radii and decay constants for S and P states of c ̅ and ̅ mesons by using the realistic and simple harmonic oscillator wave functions. The calculated results of mass, hyperfine splitting, root means square radii and decay constants agreed with experimental and theoretically calculated results in the literature.

Scattering in Classical and Quantum Physics

Scattering experiments provide the main source of information on the properties of elementary particles. Here we present the theory of scattering in both classical and non-relativistic quantum physics. We introduce the basic notions of cross section and of range and strength of interactions. We work out some illustrative examples. The concept of resonant scattering, central to almost all applications in particle physics, is explained in the simple case of potential scattering, where we derive the Breit–Wigner formula. This framework of non-relativistic potential scattering turns out to be very convenient for introducing several other important concepts and results, such as the optical theorem, the partial wave amplitudes and the corresponding phase shifts and scattering lengths. The special cases of scattering at low energies, and that in the Born approximation, are studied. We also offer a first glance at the problem of the infrared divergences for the case of Coulomb scattering.

Relativistic electric potential near a resting straight carbon nanotube of a finite-length with stationary current

Based on the Lienard – Wiechert potentials for a uniformly and rectilinearly moving electron, a relativistic electric field is studied near a densely filled with potassium atoms single-walled carbon nanotube (K@CNT) with a stationary electric current inside it. The relativistic electric field in the laboratory coordinate system arises (due to the Lorentz transformations) only for a nanotube of a finite length. This field is a result of summation of the Coulomb fields of stationary positively charged ionic cores of potassium and an equal number of ballistically moving valence electrons of potassium that create a current. It is shown that the magnitude of the negative relativistic electric potential of K@CNT in the direction perpendicular to the nanotube does not depend on the direction of the current density. The relationship is obtained between the K@CNT radius and the number of open channels of ballistic electron transfer over potassium atoms. The Landauer formula is used, which relates the number of open quasi-one-dimensional channels and the direct current electrical conduction. For the first time, analytical formulas are obtained for the dependence of the relativistic potential near K@CNT on the electric voltage between the ends of the nanotube and on its radius in the limit of zero absolute temperature. The case is considered when the distance from the point of registration of the relativistic potential above the center of the nanotube is much less than its length. For nanotube with diameter of 2 nm and length of 100 mm, under an external electric field strength of 5 mV/mm, the magnitude of the potential of the relativistic electric field is of about 2 mV. Modern measurement techniques make it possible to register the predicted relativistic potential.

Charmonium Properties

We calculated the mass spectra of charmonium meson by using matrix method to make the predictions of ground and radially excited states of charmonium mesons via non-relativistic potential model. We compared our results with other theoretical approaches and recently published experimental data. The predictions are found to be in a good accordance with the latest experimental results of Particle data group and with the results of other theoretical approaches. Besides, we calculated the momentum width coefficients β of charmonium meson. Since, there are no experimental data for the momentum width coefficients β of charmonium meson yet. Consequently, our calculated coefficients β are compared with other theoretical studies and it is found to be in a good agreement with our results. The obtained results of coefficients β have implications for decay constants, decay widths and differential cross sections for charmonium system and generally for heavy mesons system. Our study is considered as theoretical calculation of some properties of charmonium meson.

Core-collapse supernovae in the hall of mirrors

Context. Modeling core-collapse supernovae (SNe) with neutrino transport in three dimensions (3D) requires tremendous computing resources and some level of approximation. We present a first comparison study of core-collapse SNe in 3D with different physics approximations and hydrodynamics codes. Aims. The objective of this work is to assess the impact of the hydrodynamics code, approximations for the neutrino, gravity treatments, and rotation on the simulation of core-collapse SNe in 3D. Methods. We use four different hydrodynamics codes in this work (ELEPHANT, FLASH, fGR1, and SPHYNX) in combination with two different neutrino treatments, the isotropic diffusion source approximation (IDSA) and two-moment M1, and three different gravity treatments (Newtonian, 1D General Relativity correction, and full General Relativity). Additional parameters discussed in this study are the inclusion of neutrino-electron scattering via a parametrized deleptonization and the influence of rotation. Results. The four codes compared in this work include Eulerian and fully Lagrangian (smoothed particle hydrodynamics) codes for the first time. They show agreement in the overall evolution of the collapse phase and early post-bounce within the range of 10% (20% in some cases). The comparison of the different neutrino treatments highlights the need to further investigate the antineutrino luminosities in IDSA, which tend to be relatively high. We also demonstrate the requirement for a more detailed heavy-lepton neutrino leakage. When comparing with a full General Relativity code, including an M1 transport method, we confirm the influence of neutrino-electron scattering during the collapse phase, which is adequately captured by the parametrized deleptonization scheme. Also, the effective general relativistic potential reproduces the overall dynamic evolution correctly in all Newtonian codes. Additionally, we verify that rotation aids the shock expansion and estimate the overall angular momentum losses for each code in rotating scenarios.