International Journal of Modern Physics E

The ASACUSA collaboration of CERN has recently carried out two-photon laser spectroscopy of antiprotonic helium atoms. Some nonlinear two-photon transitions of the antiproton at the deep UV wavelengths λ = 139.8–197.0 nm were excited by irradiating the atom with two counterpropagating laser beams. This reduced the thermal Doppler broadening in the observed spectral lines. Three transition frequencies were thus determined with fractional precisions of 2.3–5 parts in 10⁹. By comparing the results with three-body quantum electrodynamics calculations, the antiproton-to-electron mass ratio was derived as 1836.1526736(23). In this paper, we briefly review these recent experimental results.

Forward–backward (FB) charge correlations are investigated by analyzing experimental data on ¹⁶O–AgBr interactions at 14.5A, 60A and 200A GeV. Findings are compared with the predictions of Monte Carlo model, heavy-ion jet interaction generater (HIJING). The results reveal that the observed correlations are mainly of short-range type, which arise due to the decay of clusters and/or resonances produced in the central rapidity region. The range of FB correlations are observed to extend with increasing beam energy. However, there is no evidence for the presence of long-range correlations even at the highest incident energy considered.

Galactic dark matter is matter hypothesized to account for the discrepancy of the mass of a galaxy determined from its gravitational effects, assuming the validity of Newton's law of universal gravitation, and the mass calculated from the "luminous matter", stars, gas, dust, etc. observed to be contained within the galaxy. The conclusive observation from the rotation curves of spiral galaxies that the mass discrepancy is greater, the larger the distance scales involved implies that either Newton's law of universal gravitation requires modification or considerably more mass (dark matter) is required to be present in each galaxy. Both the modification of Newton's law of gravitation and the hypothesis of the existence of considerable dark matter in a galaxy are discussed. It is shown that the Generation Model (GM) of particle physics, which leads to a modification of Newton's law of gravitation, is found to be essentially equivalent to that of Milgrom's modified Newtonian dynamics (MOND) theory, with the GM providing a physical understanding of the MOND theory. The continuing success of MOND theory in describing the extragalactic mass discrepancy problems constitutes a strong argument against the existence of undetected dark matter haloes, consisting of unknown nonbaryonic matter, surrounding spiral galaxies.

We have studied the ground state bulk properties of magnesium isotopes using axially symmetric relativistic mean field formalism. The BCS pairing approach is employed to take care of the pairing correlation for the open shell nuclei. The contour plot of the nucleons distribution are analyzed at various parts of the nucleus, where clusters are located. The presence of an ¹⁶O core along bubble like α-particle(s) and few nucleons are found in the Mg isotopes.

By using the revised Landau hydrodynamic model and taking into account the effect of leading particles, we discuss the pseudorapidity distributions of produced charged particles in high energy heavy-ion collisions. The charged particles resulted from the freeze-out of the matter produced in collisions possess the Gaussian-like rapidity distributions. The leading particles are assumed having the rapidity distributions of the Gaussian form with the normalization constant being equal to the number of participants, which can be figured out in theory. It is found that the results from the revised Landau hydrodynamic model together with the contributions from leading particles are well consistent with the experimental data carried out by BNL-RHIC-PHOBOS Collaboration in different centrality Au+Au collisions at energies of , 130 and 62.4 GeV, respectively.

Useful information about the shape transitions of even–even isotones ¹⁴⁴Ba, ¹⁴⁶Ce, ¹⁴⁸Nd, ¹⁵⁰Sm, ¹⁵²Gd, ¹⁵⁴Dy with 88 neutrons and ^218-226Ra isotopes with 88 protons are obtained from the ratios of as a function of neutron number N or proton number Z and the relations and r((I+2)/I) as a function of the angular momentum I. Interacting Boson Model (IBM-1), Bohr–Mottelson Model (BM) and Interacting Vector Boson Model (IVBM) have been employed to study the energy levels for the ground and octupole bands of the above nuclei. The best input parameters for the above approaches which lead to the best fit to experimental data are determined. The ΔI = 1 staggering (odd–even staggering) in octupole bands of the studied nuclei is found to exhibit a "beat" behavior as a function of angular momentum I. Comparisons of the displacement energies δE(I) and the staggering factor ΔE₁, γ(I) are presented between the Ba–Dy region with 88 neutrons and Ra isotopes with 88 protons.

We present a generalized variational procedure oriented to the algebraic solution of many-body Hamiltonians expressed in bosonic and fermionic variables. The method specializes in the nonperturbative regime of the solutions. As an example, we focus on the application of the method to nonperturbative QCD.