abstract

An explicit form of charged–lepton mass matrix, predicting \( m_\tau = 1776.80\) MeV from the experimental values of \(m_e\) and \(m_\mu \) (in good agreement with the experimental figure \(m_\tau =1777.05^{+0.29}_{-0.26}\) MeV), is applied to three neutrinos \(\nu _e\), \(\nu _\mu \), \(\nu _\tau \) in order to correlate tentatively their masses and mixing parameters. It is suggested that for neutrinos the diagonal elements of the mass matrix are small versus its off-diagonal elements. Under such a conjecture, the neutrino masses, lepton Cabibbo–Kobayashi–Maskawa matrix and neutrino oscillation probabilities are calculated in the corresponding lowest perturbative order. Then, the nearly maximal mixing of \(\nu _\mu \) and \(\nu _\tau \) is predicted in consistency with the observed deficit of atmospheric \(\nu _\mu \)’s. However, the predicted deficit of solar \(\nu _e\)’s is much too small to explain the observed effect, what suggests the existence of (at least) one sort, \(\nu _s^{(e)}\), of sterile neutrinos, whose mixing with \(\nu _e\) would be responsible for the observed deficit. Perspectives for applying the same form of mass matrix to quarks are also outlined. Two independent predictions of \(|V_{ub}|\)/\(|V_{cb}| = 0.0753 \pm 0.0032\) and unitary angle \(\gamma \simeq 70^\circ \) are deduced from the experimental values of \(|V_{us}|\) and \(|V_{cb}|\) (with the use of quark masses \(m_s\), \(m_c\) and \(m_b\)). In the last three Sections, the option of two sorts, \(\nu _s^{(e)}\) and \(\nu _s^{(\mu )}\), of sterile neutrinos is considered. They may dominate neutrino mixing, and even cause that two extra neutrino mass states (arising then) are agents of some tiny neutrino instability and related damping of \(\nu _e\) and \(\nu _\mu \) oscillations. In Appendix, three conventional Majorana sterile neutrinos are discussed.

abstract

The dipole fit to the proton form factor is extended impirically in a three quark analysis of the electromagnetic form factors \(G_{\rm E}\) and \(G_{\rm M}\). A relativisitic three quark Dirac shell model wave function is used to describe the quarks in the proton rest frame. Fits beyond the dipole to the electromagnetic form factors lead to the upper and lower components of the shell model wave function, and eventually to a model determination of the potentials acting on the quarks. Asymptotically the scalar potential is a confining linear potential. Its slope allows one to estimate the flux tube constant. A best fit of the electromagnetic form factors using the composite three quark wave function yields similiar values for the flux tube constant. The flux tube constant found is about one half the 0.9 GeV/fm found from meson studies.

abstract

We calculate the Casimir energy of the rotating Nambu-Goto string with the Gauss-Bonnet term in the action and point-like masses at the ends. This energy turns out to be negative for every values of the parameters of the model.

abstract

We have estimated the two gamma decay width of \(D\) meson by using the bound state model of Holdom and Sutherland. Here we have derived an effective quark level Lagrangian for \(c\rightarrow u\gamma \) and \( c\rightarrow u\gamma \gamma \) and hence we have calculated the decay width of \(D\rightarrow \gamma \gamma \). We have obtained the branching ratio for the above decay mode as: Br \((D^{0}\rightarrow 2\gamma ) = 8.63 \times 10^{-6}\).

abstract

A pseudotriangular Hopf algebra structure on a deformed Yangian \(Y_{F}(g)\) associated to a simple Lie algebra \(g\) is given by using a star-product on the corresponding simple Poisson Lie group.

abstract

A statistical model of the early stage of central nucleus–nucleus (A+A) collisions is developed. We suggest a description of the confined state with several free parameters fitted to a compilation of A+A data at the AGS. For the deconfined state a simple Bag model equation of state is assumed. The model leads to the conclusion that a Quark Gluon Plasma is created in central nucleus–nucleus collisions at the SPS. This result is in quantitative agreement with existing SPS data on pion and strangeness production and gives a natural explanation for their scaling behaviour. The localization and the properties of the transition region are discussed. It is shown that the deconfinement transition can be detected by observation of the characteristic energy dependence of pion and strangeness multiplicities, and by an increase of the event–by–event fluctuations. An attempt to understand the data on \(J/\psi \) production in Pb+Pb collisions at the SPS within the same approach is presented.

abstract

The improved method of intermittent data analysis is proposed. It exploits, in addition to the standard density moments, the information on the bin–bin correlations, observed in the data and expressed in terms of the density correlators. The improving recovering corrections are implemented into the data analysis in the form of the recursive algorithm, and tested in the framework of multiplicative cascading models.

abstract

We study the influence of a high density behaviour of the nuclear symmetry energy on a kaon condensation in neutron stars. We find that the symmetry energy typical for several realistic nuclear potentials, which decreases at high densities, inhibits kaon condensation for weaker kaon–nucleon couplings at any density. There exists a threshold coupling above which the kaon condensate forms at densities exceeding some critical value. This is in contrast to the case of rising symmetry energy, as e.g. for relativistic mean field models, when the kaon condensate can form for any coupling at a sufficiently high density. Properties of the condensate are also different in both cases.

abstract

We present an event-by-event analysis of the cluster structure of final multihadron states resulting from heavy ion collisions. A comparison of experimental data with the states obtained from Monte Carlo generators is shown. The analysis of the first available experimental events suggests that the method is suitable for selecting some different types of events.

abstract

The excited states of \(^{93}\)Mo have been investigated via \(^{93}\)Nb \((p,n\gamma \))\(^{93}\)Mo reaction with the proton beam energies from 2.7–4.3 MeV. The angular distributions have been used to assign the spins and the multipole mixing ratios using statistical theory for compound nuclear reactions. The ambiguity in the spin values for the 2181.3, 2247.3 and 2539.3 keV levels have been removed. The multipole mixing ratios eight \(\gamma \)-transitions have been newly measured. The lifetimes of the levels at 2539.3 and 2642.0 keV have been measured for the first time using Doppler shift attenuation method. The experimental results are compared with the existing theoretical models.

abstract

The isospin and spin dependence of the real part of the single-particle potential of a \({\mit \Sigma }\) hyperon in nuclear matter, \(\hat {V}_{\mit \Sigma }\), is investigated. The isospin, spin, and spin-isospin dependent parts \(V_\tau \), \(V_\sigma \), and \(V_{\sigma \tau }\) of \(\tilde {V}_{\mit \Sigma }\) are expressed in terms of an effective \({\mit \Sigma } N\) interaction in nuclear matter. With suitable approximations numerical results for \(V_\tau \), \(V_\sigma \), and \(V_{\sigma \tau }\) are obtained for four models of the Nijmegen baryon-baryon interaction. A comparison with recent \((K^-,\pi ^\pm )\) experiments favors model F as a realistic representation of the \({\mit \Sigma } N\) interaction.

abstract

High quality quantum wires conductance measurements have revealed an unexpected feature: the quantization step of the conductance is apparently system dependent. We show that even a single impurity (modelled by a short range potential) in a wire leads to enhanced backscattering and affects the conductance steps. We construct a random matrix model which shows similar behaviour with the size of conductance step dependent on a single parameter.