International Journal of Modern Physics E

The recent discussion about experimental evidence for pentaquark states has revitalized the interest in exotic hadrons. If such states really exist, it is natural to assume that they will be formed at the late hadronization stage of ultra-relativistic heavy ion collisions, given the success of quark recombination models in the description of hadronization. Here, we apply the qMD model to study the formation of color neutral exotic multi-quark clusters at hadronization. We search for color neutral clusters made up of up to six color charges, respectively. We thus obtain estimates for the numbers and phase space distributions of exotic hadronic states produced by clustering in heavy ion collisions, including the members of the pentaquark multiplets. We obtain particle abundances that are smaller than thermal model predictions. Moreover, the results obtained in recombination from ultra-relativistic heavy ion collisions can be compared to the estimates based on equal population of the corresponding multiplets, and to results from fully thermalized systems. We find that the distribution of exotic hadrons from recombination over large multiplets provides a sensitive signal for thermalization and decorrelation of the initial, non-equilibrium state of the collision.

The "electroweak connection", which forms one of the cornerstones of the Standard Model of particle physics, is formulated within the framework of the Generation Model. It is shown that the electroweak connection can be derived assuming that the weak interactions are effective interactions rather than fundamental interactions, arising from a U(1)×SU(2) local gauge invariance, which is spontaneously broken by a Higgs field.

The well known and analytically solvable Lipkin–Meshkov–Glick model was devised to test several many-body approximation approaches used in nuclear physics. Here, we use this model to illustrate a method that sets lower bounds for the ground state energy of a quantum Hamiltonian. The idea of the method consists of dividing the Hamiltonian into identical groups of terms that represent subdivisions in the particle population of the system, and then to make an appropriate use of the ground energy of one of these groups. The bounds clearly improve as the size of these groups increases.

In this article, we investigate the contribution of the high twist Feynman diagrams to the large-p_T single pseudoscalar and vector mesons inclusive production cross section in two-photon collisions and we present the general formulae for the high and leading twist differential cross sections. The pion wave function where two non-trivial Gegenbauer coefficients a₂ and a₄ have been extracted from the CLEO data, Braun–Filyanov pion wave function, the asymptotic and the Chernyak–Zhitnitsky wave functions are all used in the calculations. For ρ-meson we used the Ball–Braun wave function. The results of the calculations reveal that the high twist cross sections, the ratio R, the dependence transverse momentum p_T and the rapidity y of meson in the Φ_CLEO(x, Q²) wave function case is very close to the Φ_asy(x) asymptotic wave function case. It is shown that the high twist contribution to the cross section depends on the choice of the meson wave functions.

The decay of ⁷²As has been investigated by means of γ-ray spectroscopy. The ⁷²As nuclei were produced through the ⁷²Ge(p, n)⁷²As reaction. The Compton-suppressed spectrometer and high-purity Ge detectors have been used in singles and in coincidence modes respectively to study γ-rays in the β⁺+EC decay of ⁷²As to ⁷²Ge. 79 γ-rays, among which 3 were observed for the first time, were reported. A decay scheme of ⁷²As including 1 new level is proposed that accommodates 77 of these transitions. Tentative spin and parity assignments are suggested for a number of levels according to the log ft values and γ-branching ratios.

We show that the principle of entropy increase may be exactly founded on a few axioms valid not only for quantum and classical statistics, but also for a wide range of statistical processes.

The medium effect of in-medium nucleon–nucleon cross section on the isoscaling parameter α is investigated for two couples of central nuclear reactions ⁴⁰Ca+⁴⁸Ca and ⁶⁰Ca+⁴⁸Ca; ¹¹²Sn+¹¹²Sn and ¹²⁴Sn+¹²⁴Sn at beam energy region from 40 to 60 MeV/nucleon with isospin dependent quantum molecular dynamics. It is found that there is the obvious medium effect of on the isoscaling parameters α. The mechanism for the medium effect of on α is investigated.

The neutron emission spectrum of the highly excited compound nuclear system ¹³²Sn is investigated at high spin. The doubly magic nucleus ¹³²Sn undergoes a shape transition at high angular momentum which affects the nuclear level density and neutron emission probability considerably. The interplay of temperature, shape, deformation and rotational degrees of freedom and their influence on neutron emission is emphasized. We predict an enhancement of nucleonic emission at those spins where the nucleus suffers a transition from a spherical to deformed shape.

The one-dimensional semi-relativistic equation has been solved for the -symmetric generalized Hulthén potential. The Nikiforov–Uvarov (NU) method which is based on solving the second-order linear differential equations by reduction to a generalized equation of hypergeometric type, is used to obtain exact energy eigenvalues and corresponding eigenfunctions. We have investigated the positive and negative exact bound states of the s-states for different types of complex generalized Hulthén potentials.

In quantum mechanics the hyper-spherical method is one of the most well-established and successful computational tools. The general theory of harmonic polynomials and hyper-spherical harmonics is of central importance in this paper. The interaction potential V is assumed to depend on the hyper-radius ρ only where ρ is the function of the Jacobi relative coordinate x₁, x₂,…, x_n which are functions of the particles' relative positions.

Brajinskii's equations are the fundamental relations governing the behavior of the plasma produced during a fusion reaction, especially ICF plasma. These equations contains six partial differentials coupled together. In this paper we have tried to give analytical solutions to these equations using a one-dimensional method. Laplace transform technique is the main tool to do that with an arbitrary boundary and initial conditions for some special cases.

The ⁹⁷Mo nucleus has been studied with the reaction ⁹⁵Mo (t, p) ⁹⁷Mo using a multichannel magnetic spectrograph. The isotopically enriched thin target ⁹⁵Mo was bombarded with the 12 MeV triton beam obtained from the tandem Van de Graaff accelerator at the Atomic Weapon Research Establishment, Aldermaston. Proton spectra are obtained at 12 different angles from 5° to 87.5° at an interval of 7.5° and are detected in nuclear emulsion plates. Forty-eight levels in the energy range from 0.000 to 3.189 MeV have been observed. Absolute differential cross-sections for these levels have been measured. The angular distributions are compared with the theoretical distorted-wave Born approximation calculations to determine L and J^π values. The nuclear properties of ⁹⁷Mo are compared with previous experimental results and model predictions.