'Mass

[eveningmass79]

Single and double coincidence nucleon spectra in the weak decay of Λ-hypernuclei are studied within a nuclear matter formalism extended to finite nuclei via the local density approximation. With respect to previous calculations, the present work adopts a unified microscopic approach for both the one- and two-body induced mechanisms, including the channels Λnn→nnn and Λpp→npp in addition to the mode Λnp→nnp already considered in earlier phenomenological studies. The propagation of the final nucleons in the residual nucleus is simulated by an intranuclear cascade code. Through the comparison of our predictions with 12ΛC KEK nucleon coincidence data obtained with a nucleon kinetic energy threshold of 30 MeV and an opening angle region we determine Γn/Γp=0.66±0.24. We find that the value of Γn/Γp extracted from single nucleon distributions is strongly affected by final state interaction effects. Some discrepancies between measured and calculated proton spectra are also pointed out.

[eveningmass79]

A geometric analysis of the sdg interacting boson model is performed. A coherent state is used in terms of three types of deformation: axial quadrupole (β2), axial hexadecapole (β4) and triaxial (γ2). The phase-transitional structure is established for a schematic sdg Hamiltonian which is intermediate between four dynamical symmetries of U(15), namely the spherical U(5)U(9), the (prolate and oblate) deformed SU±(3) and the γ2-soft SO(15) limits. For realistic choices of the Hamiltonian parameters the resulting phase diagram has properties close to what is obtained in the sd version of the model and, in particular, no transition towards a stable triaxial shape is found.

[eveningmass79]

We analyze the 12Be spectrum with two microscopic methods. Microscopic cluster calculations are performed within the Generator Coordinate Method (GCM) framework. An extended two-cluster model which includes the , and channels is developed. It represents an extension of a previous work by Descouvemont and Baye where only the 0+ ground states of 8He and 6He were taken into account. The GCM calculations lead to a good description of the molecular band suggested by Freer et al. and by Saito et al. The isomeric state and the state are also well described by the GCM. New bands of positive and negative parities are proposed. This approach is complemented by No-Core Shell Model (NCSM) calculations, in order to clarify the structure of the ground state and the hypothesis of an associated rotational band. The GCM and NCSM calculations do not support the existence of a band built on the ground state.

[eveningmass79]

We use a recently improved density-matrix expansion to calculate the nuclear energy density functional in the framework of in-medium chiral perturbation theory. Our calculation treats systematically the effects from 1π-exchange, iterated 1π-exchange, and irreducible 2π-exchange with intermediate Δ-isobar excitations, including Pauli-blocking corrections up to three-loop order. We find that the effective nucleon mass M*(ρ) entering the energy density functional is identical to the one of Fermi-liquid theory when employing the improved density-matrix expansion. The strength F(ρ) of the surface-term as provided by the pion-exchange dynamics is in good agreement with that of phenomenological Skyrme forces in the density region ρ0/2<ρ<ρ0. The spin–orbit coupling strength Fso(ρ) receives contributions from iterated 1π-exchange (of the “wrong sign”) and from three-nucleon interactions mediated by 2π-exchange with virtual Δ-excitation (of the “correct sign”). In the region around ρ0/20.08 fm−3 where the spin–orbit interaction in nuclei gains most of its weight these two components tend to cancel, thus leaving all room for the short-range spin–orbit interaction. The strength function FJ(ρ) multiplying the square of the spin–orbit density comes out much larger than in phenomenological Skyrme forces and it has a pronounced density dependence.

[eveningmass79]

The range corrections to the universal properties and structure of two-neutron halo nuclei are investigated within an effective quantum mechanics framework. Treating the nucleus as an effective three-body system, we make a systematic improvement upon previous calculations by calculating the linear range corrections at next-to-leading order. Since the effective ranges for the neutron–core interactions are not known, we estimate the effective range to be set by the inverse of the pion mass. We investigate the possibility of excited Efimov states in two-neutron halo nuclei and calculate their mean square radii to next-to-leading order. We find that the effective range corrections are generally small and the leading order predictions are very robust.

[eveningmass79]

Energy loss of a jet due to multiple collisions in the nuclear target is studied in the framework of the perturbative QCD with an infrared cutoff. An iterational procedure for its calculation is developed, which allows to reliably find up to 16 successive collisions in rescattering. The calculated shift of the scaling variable reaches values of the order 0.1 at medium x and transverse momentum p in the interval 5–10 GeV/c. The shift is found to be independent of the atomic number of the target and energy.

[eveningmass79]

We compute the electric-current susceptibility χ of hot quark–gluon matter in an external magnetic field B. The difference between the susceptibilities measured in the directions parallel and perpendicular to the magnetic field is ultraviolet-finite and given by , where V denotes the volume, T the temperature, Nc the number of colors, and qf the charge of a quark of flavor f. This non-zero susceptibility difference acts as a background to the Chiral Magnetic Effect, i.e. the generation of electric current along the direction of magnetic field in the presence of topological charge. We propose a description of the Chiral Magnetic Effect that takes into account the fluctuations of electric current quantified by the susceptibility. We find that our results are in agreement with recent lattice QCD calculations. Our approach can be used to model the azimuthal dependence of charge correlations observed in heavy ion collisions.

[jazluvr]

Flexing our intellectual muscles are we? Lol.