Table of contents

Using the reaction ⁹Be(d,p)¹⁰Be (Q = 4.59 MeV) at E_d = 1.0 MeV, the energy of the first excited state in ¹⁰Be was found to be 3368.34±0.43 keV, in excellent agreement with the literature value. The result strengthens conclusions derived from recent studies of the cold ternary spontaneous fission of ²⁵²Cf.

A generalization of the Van der Waals excluded-volume procedure for the multicomponent hadron gas is proposed. The derivation is based on the grand canonical partition function for the system of particles of several species interacting by hard-core potentials. The obtained formulae for thermodynamical quantities are consistent with underlying principles of statistical mechanics as well as with thermodynamical identities. The model can be applied to the analysis of experimental data for particle number ratios in relativistic nucleus-nucleus collisions.

The new contributions to the charmless B decay BX_s´ from the unit-charged technipions P^± and P₈^± are estimated. The technipions can provide a large enhancement to the inclusive branching ratio: Br(BX_s^´)~7 x 10^-4 for m_p1 = 100 GeV and m_p8 = 250-350 GeV when the effect of QCD gluon anomaly is also taken into account. The new physics effect is essential to interpret the CLEO data.

Neutron stars, spotted as pulsars by radio telescopes and x-ray satellites, contain matter up to ten times denser than atomic nuclei, thus providing a high-pressure environment in which numerous subatomic particle processes are expected to compete with each other and novel phases of matter - like the quark-gluon plasma being sought at the most powerful terrestrial particle colliders - could exist. This article aims at exploring the possible existence of quark matter inside neutron stars and pointing out the fingerprints by means of which this novel phase of matter could register itself in the observed pulsar data. The detection of such matter in neutron stars would help to clarify how quark matter behaves, and give a boost to theories about the early universe as well as laboratory searches for the production of quark matter in heavy-ion colliders.

We systematically embed the SU(2) × U(1) Higgs model in the unitary gauge into a fully gauge-invariant theory by following the generalized BFT formalism. We also suggest a novel path to get a first-class Lagrangian directly from the original second-class one using the BFT fields.

Neutral fermions of spin-½ with magnetic moment can interact with electromagnetic fields through nonminimal coupling. In 2 + 1 dimensions the electromagnetic field strength plays the same role to the magnetic moment as the vector potential to the electric charge. This duality enables one to obtain physical results for neutral particles from known ones for charged particles. We give the probability of neutral particle-antiparticle pair creation in a vacuum by non-uniform electromagnetic fields produced by constant uniform charge and current densities.

We study Schwinger-Dyson equations for fermions in Yukawa and Wess-Zumino models, in terms of dynamical mass generation and the wavefunction renormalization function. In the Yukawa model with ₅-type interaction between scalars and fermions, we find a critical coupling in the quenched approximation above which fermions acquire dynamical mass. This is shown to be true beyond the bare 3-point vertex approximation. In the Wess-Zumino model (Wess J and Zumino B 1974 Nucl. Phys. B 70 39; Wess J and Zumino B 1974 Phys. Lett. B 49 52), there is a neat cancellation of terms leading to no dynamical mass for fermions. We comment on the conditions under which these results are general beyond the rainbow approximation and also on the ones under which supersymmetry is preserved and the scalars do not also acquire mass. The results are in accordance with the non-renormalization theorem at least to order in perturbation theory. In both the models, we also evaluate the wavefunction renormalization function, analytically in the neighbourhood of the critical coupling and numerically, away from it.

The H-dihyperon (DH) is studied in the framework of the SU(3) chiral quark model. It is shown that, with the exception of the chiral field, the overall effect of the other SU(3) chiral fields is destructive in forming a stable DH. The resultant mass of DH in a three-coupled channel calculation ranges from 2225-2234 MeV.

We calculate the neutron electric dipole moment (EDM) in the left-right supersymmetric model, including one-loop contributions from the chargino, the neutralino and the gluino diagrams. We discuss the dependence of the EDM on the phases of the model, as well as on the mass parameters in the left and right sectors. The neutron EDM imposes different conditions on the supersymmetric spectrum from either the electron EDM, or the neutron EDM in the minimal supersymmetric standard model. The neutron EDM may be a clue to an extended gauge structure in supersymmetry.

The quon algebra, which interpolates between the Bose and Fermi algebras and depends on a free parameter q, is used to generate a Marumori mapping of the quadrupole-quadrupole Hamiltonian, for a single j-shell. This Hamiltonian is then diagonalized for a system composed of six fermions and its eigenvalues are compared with the ones obtained from the counterpart fermionic Hamiltonian and with another usual boson expansion method. The deformed mapping is shown to require a larger basis than the usual Marumori method for the diagonalization of the Hamiltonian. The low-lying levels of the spectrum obtained from the fermionic calculation in the SD subspace can be reproduced with our mapping for some selected j-shells.

The -spectrum of ²⁴¹Pu with the endpoint energy of 20.8 keV was measured in the energy range from 0.2 to 9.2 keV. The spectra were recorded during 5700 h with an electrostatic spectrometer set to a resolution of E/E = 0.011. Electron energy losses within the radioactive source were treated by means of extensive Monte Carlo simulations of individual elastic and inelastic electron collisions. The upper limit for the admixture of hypothetical neutrinos with the rest masses between 14 and 17 keV/c² was derived to be less than 0.40% (the lowest limit being 0.10% for the 16 keV/c² mass) at the 95% C.L., independently of any free phenomenological parameter.

Hadron-hadron (h-h) collisions at high energies are investigated in the ultra-relativistic quantum molecular dynamics (UrQMD) approach. This microscopic transport model describes the phenomenology of hadronic interactions at low and intermediate energies (<5 GeV) in terms of interactions between known hadrons and their resonances. At higher energies, >5 GeV, the excitation of colour strings and their subsequent fragmentation into hadrons dominates the multiple production of particles in the UrQMD model. The model shows a fair overall agreement with a large body of experimental h-h data over a wide range of h-h centre-of-mass energies. Hadronic reaction data with higher precision would be useful to support the use of the UrQMD model for relativistic heavy-ion collisions.

The ²⁸Si( ⁷Li,t) ³²S reaction has been studied at 48 MeV. Using a t potential overlap based on a microscopic cluster model, the full finite-range distorted wave Born approximation analysis was carried out for nine low-lying states; 0.0 MeV (0⁺), 2.23 MeV (2⁺), 3.78 MeV (0⁺), 4.46 MeV (4⁺), 5.01 MeV (3^-), 5.80 MeV (1^-), 6.76 MeV (3^-), 7.43 MeV (1^-) and 8.49 MeV (1^-) of the residual nucleus. A re-analysis was also done for the same states of ³²S having an d overlap for the reaction ²⁸Si (⁶Li, d) ³²S at 75.6 MeV. Theoretical spectroscopic factors have been calculated for the measured even-parity states of ³²S using the shell model code OXBASH. The spectroscopic factors were compared for both the reactions.

Using the exact transmission coefficient across an asymmetric parabolic barrier derived by Zafar Ahmed and the ideas used earlier in our effective fusion barrier transmission model we develop a new asymmetric parabolic effective fusion barrier model for heavy ion fusion. A closed form expression for fusion cross section (_F) depending only on the s-wave characteristics of the fusion barrier is derived. The expected change of shape of the barrier in the interior side due to channel coupling is represented by a variable curvature parameter ₂ whereas the outer curvature ₁ is kept unchanged. We apply this model to fit the fusion data, namely fusion cross section, spin distribution, average angular momenta and barrier distribution, in the cases of the following representative pairs of nuclei at energies around the Coulomb barrier: ¹⁶O+ ¹⁴⁴Sm, ¹⁶O+ ¹⁵²Sm, ⁴⁰Ca+ ^46,48,50Ti, ⁵⁸Ni+ ⁶⁴Ni and ⁶⁴Ni+ ⁹²Zr. These examples include cases of symmetric, asymmetric and nearly symmetric fusion. We obtain good fits to the experimental data. The asymmetry parameter = (₂/₁) ^1/2 used in the present macroscopic formulation is correlated to the order of coupling in coupled channel calculations.

The ¹²C+ ¹²C excitation functions have been studied for unbound inelastic channels at centre-of-mass energies between 35 and 45 MeV and for transfer channels between 30 and 60 MeV, in steps of 250 keV. Results are presented for the inelastic channels (0⁺₁,0⁺₂), (0⁺₁,3^-₁) and (0⁺₁,4⁺₁) to the unbound ¹²C states above the -particle decay threshold and for the one- and two-nucleon transfer channels. Intermediate-structure resonances tend to disappear above E_c.m. = 35 MeV, while a broad structure becomes a general feature of the interaction at higher energies.

The variational principle for the special and general relativistic hydrodynamics is discussed in view of its application to obtain approximate solutions to these problems. We show that effective Lagrangians can be obtained for suitable ansatze for the dynamical variables such as the density profile of the system. As an example, the relativistic version of spherical droplet motion (Rayleigh-Plesset equation) is derived from a simple Lagrangian. For the general relativistic case the most general Lagrangian for spherically symmetric systems is given.

We study the breakup of ⁹Li projectiles in high-energy (28.5 MeV/u) collisions with heavy nuclear targets (²⁰⁸Pb). The wavefunctions are calculated using a simple potential model for ⁹Li. A good agreement with the measured data is obtained with insignificant E2 contribution.

The method of equivalent quanta is applied both to photon-photon and, by analogy, to double pomeron exchange in heavy-ion collisions. This Weizsäcker-Williams approach is used to calculate production cross sections for the glueball candidate f_J(1710) meson via photon-photon and pomeron-pomeron fusion in peripheral heavy-ion collisions at both RHIC and LHC energies. The impact parameter dependence for total and elastic cross sections is presented, and compared with results for proton-proton collisions.

Quasi-monochromatic photon beams of 108 MeV Compton-edge energy produced in the ROKK-1M facility at the storage ring VEPP-4M (BINP, Novosibirsk) and makrofol sheets as fission track detectors were used to measure the photofission yield of ²⁷Al. The fission yield was found to be (160±55) µb. From this result and previously measured ²⁷Al photofission yield at ~79 MeV end-point energy with the LADON apparatus, the trends of fission cross section and fissility have been obtained in the incident photon energy range ~40-110 MeV. The present results and data for other intermediate-mass nuclei obtained with the same methodology indicate an increase of fissility with decreasing Z²/A as predicted by the liquid drop model for fissioning systems lighter than ~Ag.

The sensitivity of imaging atmospheric Cerenkov telescopes (IACTs) in TeV -ray observations reaches its maximum at small zenith angles (SZAs) ( 30^o) which provides the minimum attainable energy threshold of an instrument. However, for a specific telescope site a number of -ray sources, or source candidates, can only be observed at much larger zenith angles (LZAs) ( 60^o). Moreover, the observations at LZAs allow us to extend the observation time window for any object seen at SZAs, as well as to enlarge the dynamic energy range of an instrument towards the highest observable energies of -rays. Based on Monte Carlo simulations we present the results on the sensitivity of a stereoscopic system of five IACTs in observations at LZAs. We point out some important parameters of the telescope design which could substantially improve the efficiency of such observations with forthcoming IACT arrays like CANGAROO III, HESS and VERITAS.

A detailed analysis of the world's data on ultra-high energy cosmic rays, which come from measurements of extensive air showers, reveals clear evidence for anisotropies in their arrival directions at energies below about 10¹⁹ eV. Confidence in this conclusion comes from consistency, within the errors, of the results from the different experiments and a correlation between independent indicators of anisotropy.

Although models of the Galactic magnetic field topology are not yet precise, we have used one such to estimate the fraction of cosmic rays which are light nuclei as a function of energy.