A model for the packing of irregularly shaped grains

In this paper we will attempt to address the problem of the packing properties of granular materials composed of irregularly shaped grains (using configurational statistical mechanics). In particular, we will develop a model for a system of irregular grains based upon perturbing a packing of mono- or poly-disperse spheres. In the mono-disperse case we will show that the system packs less densely than a packing of perfect spheres, except when local correlations between configurations of grains are taken into account. The opposite is found to be true for a perturbation expansion based upon poly-disperse spheres. Finally we will show that for a bi-disperse packing of spheres phase segregation occurs for any size ratio and discuss whether this is to be expected.     

The statistical mechanics of granular systems composed of elongated grains

In this paper we will suggest a model for the packing properties and phase behaviour of a granular material whose constituents are elongated in nature, using the concepts of configurational statistical mechanics. We will show that, depending upon the shape of the grains, the systems need not necessarily undergo a discontinuous first-order phase transition (even at minimum close packing). We will also briefly discuss the relationship between this model and more conventional models, such as Onsager's hard rod model.     

Alpha-particle inelastic scattering form factors in the Coulomb-nuclear interference region

Alpha-particle scattering cross sections have been measured at 15, 18 and 19 MeV from the ground state and first excited state of ⁵²Cr, ⁵⁶Fe, ⁶⁰Ni and ⁶⁴Zn. Excitation functions have also been measured for inelastic α-scattering from ⁵²Cr and ⁶⁰Ni. The data extends into the forwardangle Coulomb-nuclear interference region. The results are analysed with the optical model and DWBA, using the deformed potential model. The relative and absolute magnitudes of the nuclear and Coulomb deformation parameters and the shapes of the form factors have been deduced from the data. The importance of data in the Coulomb-nuclear interference region in determining these quantities is demonstrated.     

Peripheral pn production and decay angular distributions in the reaction π−p → (pn)p at 12 GeV/c incident momentum

The reaction $\text{π}{}^{\mathrm{?}}\text{p}\text{→ (}\text{p}\text{n}\text{)}\text{p}{}_{\mathrm{s}}$, where p_s is a slow proton, was measured at 12 GeV/c incident momentum with the CERN-OMEGA spectrometer. Both antiproton and proton were identified uniquely by electronics information. We obtained 1844 events with four-momentum Transfer squared in the range 0.13 ? |t| ? 0.33 GeV² and with invariant masses $\text{M(}\text{p}\text{n}\text{)}$ up to 2.5 GeV. The corresponding cross section in this t range is determined to be σ = 4 ± 0.4 μb. Extrapolating the differential cross section over the whole t range assuming dσ/dt ≈ exp(5.3t) we estimate a cross section of σ = 9.3 ± 2.0 μb. Comparison with data on $\text{π}{}^{\mathrm{?}}\text{p}\text{→ (}\text{p}\text{p}\text{)}\text{n}{}_{\mathrm{s}}$ (where n_s is a slow neutron) in the same t range shows that the $\text{(}\text{p}\text{n}\text{)}\text{p}{}_{\mathrm{s}}\text{and}\text{(}\text{p}\text{p}\text{)}\text{n}{}_{\mathrm{s}}$ cross sections have approximately the same magnitude.     

Charm dimuons and determination of the strange sea

We re-examine the standard charm model for opposite-sign dimuon events in neutrino-nucleon scattering. Published dimuon rates are shown to be consistent with a simple SU(3) symmetric sea. We discuss the types of correlated studies of different dimuon observables needed to extract unambiguous information on the nucleon's strange sea from upcoming, high statistics data. Our calculations demonstrate the sizeable effects of finite energy resolution and missing final-state energy on predictions of observed dimuon rates, particularly for data obtained from wide-band incident neutrino spectra. We emphasize the crucial role of the non-zero charm mass, not only for the analysis of dimuon events, but also for the interpretation of large-y inclusive $\text{v}\text{N}\text{→}\text{μ}\text{X}$ data.