Search for hyperdeformed structures populated in the <Superscript>37</Superscript>Cl+<Superscript>120</Superscript>Sn reaction by using EUROBALL III

The ridge structure with ΔE_γ=±30 keV, observed in the past in coincidence with protons emitted in the reaction 187 MeV ³⁷Cl +¹²⁰Sn and attributed to an hyperdeformed nuclear shape in ¹⁵²Dy, has been studied in a new experiment performed with the EUROBALL III array. The ridge is now observed in coincidence with transitions in the yrast superdeformed band of ¹⁵²Dy but no discrete rotational bands have been identified. Received: 7 February 2000     

Modelling the nucleon wave function from soft and hard processes

Current light-cone wave functions for the nucleon are unsatisfactory since they are in conflict with the data of the nucleon’s Dirac form factor at large momentum transfer. Therefore, we attempt a determination of a new wave function respecting theoretical ideas on its parameterization and satisfying the following constraints: It should provide a soft overlap contribution to the proton’s form factor in agreement with data; it should be consistent with current parameterizations of the valence quark distribution functions and lastly it should provide an acceptable value for theJ/ψ → N N decay width. The latter process is calculated within the modified perturbative approach to hard exclusive reactions. A simultaneous fit to the three sets of data leads to a wave function whosex-dependent part, the distribution amplitude, shows the same type of asymmetry as those distribution amplitudes constrained by QCD sum rules. The assymetry is however much more moderate as in those amplitudes. Our distribution amplitude resembles the asymptotic one in shape but the position of the maximum is somewhat shifted.     

Hafnium nitride with thorium phosphide structure: physical properties and an assessment of the Hf-N,Zr-N,and Ti-N phase diagrams at high pressures and temperatures

The physical properties of the new cubic phase of Hf3N4 as well as of isomorphic Zr3N4 and Ti3N4 are studied using first-principles calculations. Hf3N4, Zr3N4, and Ti3N4 are semiconductors with band gaps of 1.8, 1.1, and 0.6 eV, respectively. The band structure is characterized by the simultaneous presence of steep and extremely flat bands. The calculated shear modulus G indicates that the cubic Hf3N4 will be harder than the mononitride HfN. At ambient conditions, the cubic modifications of M3N4 (M=Hf, Zr, Ti) are metastable with respect to orthorhombic M3N4 phases, but the orthorhombic phases of Hf3N4 and Zr3N4 are stable with respect to the mononitrides and nitrogen.     

PD-sets for the codes related to some classical varieties

We generalize the notion of a PD-set of a code to that of a t-PD-set of an arbitrary permutation set. We find PD-sets for miquelian Benz planes of small order and for the ruled rational normal surface of order 3 in PG(4,3) and in PG(4,4). These results yield PD-sets for the related linear codes.     

Solid-on-solid model for the interface pinning transition in Ising ferromagnets

The transition associated with the pinning of a domain wall in a two-dimensional Ising ferromagnet with a free surface is studied using a discrete solid-on-solid model. The corresponding Sine-Gordon model is also briefly discussed.     

A realistic calculation of the azimuthal asymmetry in semi-inclusive deep inelastic scattering

The azimuthal asymmetry in deep inelastic scattering is calculated in first order QCD for nonvanishing intrinsic transverse momentum; the hadronization is simulated with a Monte-Carlo program. It turns out that, within our scheme, the asymmetry data are mainly sensitive to the intrinsic transverse momentum. The QCD contribution to the asymmetry is small.     

A method for the calculation of Coulomb interference and rescattering corrections to total cross sections in pure spin states

We propose a dispersion theoretic approach to the calculation of Coulomb interference and rescattering corrections to total cross sections in pure spin states. Both types of corrections can be carried out only if the real parts of the forward amplitudes are known, which in general is not the case. However, we show that under some assumptions the unknown real parts enter linearly, which together with analyticity leads to a uniquely solvable integral equation. Our approach is particularly useful in pp and pd scattering where corresponding measurements have been or will be performed. Some applications are discussed.