118027838
Structure of Co-65,Co-67 studied through the beta decay of Fe-65,Fe-67 and a deep-inelastic reaction
The neutron-rich isotopes {sup 65,67}Fe and {sup 65}Co have been produced at the LISOL facility, Louvain-La-Neuve, in the proton-induced fission of {sup 238}U. Beams of these isotopes have been extracted with high selectivity by means of resonant laser ionization combined with mass separation. Yrast and near-yrast levels of {sup 65}Co have also been populated in the {sup 64}Ni+{sup 238}U reaction at Argonne National Laboratory. The level structure of {sup 65}Co could be investigated by combining all the information from both the {sup 65}Fe and {sup 65}Co{beta} decay and the deep-inelastic reaction. The {sup 65}Fe, {sup 65}Co, and {sup 67}Fe decay schemes and the {sup 65}Co yrast structure are fully established. The {sup 65,67}Co level structures can be interpreted as resulting from the coexistence of core-coupled states with levels based on a low-energy proton-intruder configuration.
7752926
Possible dynamic effects in the particle decay of 59Cu compound nuclei.
The slopes of the energy spectra of {ital p}, {ital d}, {ital t}, and {alpha} particles emitted from {sup 59}Cu nuclei formed in the reaction of {sup 32}S+{sup 27}Al at a bombarding energy of 150 MeV are described by statistical-model calculations in which the deformation is frozen during the first two steps of the deexcitation chain. The resultant fits to the high-energy portions of the spectra are comparable to those previously obtained by modifying the spin dependence of the level density, suggesting that dynamic effects may be important in evaporation from light nuclei.
36391679
Investigation of pion absorption in heavy-ion induced subthreshold pi 0 production.
We present results from an experimental study of reabsorption effects in subthreshold pi0 production in the reaction Xe-129 + Au-197 at 44 MeV/nucleon. Within the picture of pion generation in nucleon-nucleon scattering we deduce, from our data and from a comparison with the systematics of production cross sections available for lighter reaction systems, information on the pi0 absorption length in nuclear matter. For the pi0 kinetic-energy range congruent-to 5-100 MeV the energy-averaged lambda(abs) and its momentum dependence are obtained, and compared with optical-model calculations.
40623384
Yrast isomers in exotic N=81 nucleus 151Yb studied using a fragment mass analyzer.
9087855
Gamma ray studies of neutron-rich sdf shell nuclei produced in heavy ion collisions.
Reanalysis of [ital ichproductsofbinaryreactio] [ital nsof]$[sup 34]S, [sup 36]S, and [sup 37]Cl beams on [sup 160]Gd targets. Gates set on known [ital amma]$[ital raysin]$[ital A][similar to]160 products selected individual react ion channels and identified coincident [ital amma]$[ital raysin]$[ital A][similar to]36 partner products. Transfers of protons from projectile to target and of neutrons from target to projectile were generally favored, leading to excited neutron-rich light nuclei, including some difficult to reach by other means. Notable results include the observation of [ital amma]$[ital raycascadesup][sup [ital t][ital h][ital e]][ital high] [ital e] [ital stknownyraststatesinfour]$[ital N]=20 isotones. In two [ital N]=19 nuclei, [sup 33]Si and [sup 34]P, the two [ital N]=22 nuclei, [sup 38]S and [sup 39]Cl, previously unknown yrast states were identified.
38753635
Shapes of 59Cu nuclei at moderate excitation energies and spin.
Continuum {gamma}-ray spectra from the decay of {sup 59}Cu formed at excitation energies of 54 and 74 MeV and angular momenta up to 40{h bar} have been measured and analyzed. The parameters of the giant dipole resonance have been extracted using the statistical model. The giant dipole resonance parameters for the lower excitation energy agree well with published data for spherical {sup 63}Cu nuclei. At the higher excitation, the giant dipole resonance strength distribution is not described by a single Lorentzian fit in disagreement with the findings for {sup 63}Cu at the same excitation energy. This seems to be correlated with the onset of spin driven deformations as recently evidenced from the shapes of evaporative particle spectra.
118615935
Supersymmetric dark matter sectors
We investigate the properties of a dark matter sector where supersymmetry is a good symmetry. In this context we find that the stability of the dark matter candidate is possible even when R-parity is broken in the visible sector. In order to illustrate the idea we investigate a simple scenario where the dark matter candidate is the lightest scalar field in the dark sector which annihilates mainly into two sfermions when these channels are available. We study the relic density constraints and the predictions for the dark matter detection experiments.
119194544
Prospects and constraints for vector-like MFV matter at LHC
We examine the prospects for LHC discovery of SU(2)L singlet vector-like quarks that obey Minimal Flavour Violation (MFV) and are consistent with lower energy phenomenology. We study models where the vector-like quarks have the same quantum numbers as uR or dR, allowing mixing, which generally leads to significant low energy constraints. We find that at leading order in the MFV expansion there are two naturally phenomenologically viable MFV models of this type when the Weyl spinor components of the vector-like quarks are flavour triplets. We examine direct production bounds, flavour and electroweak precision data constraints for these models and determine the cross section for allowed values of the model parameters at LHC. For the models we identify as naturally phenomenologically viable, large amounts of parameter space afford a significant early discovery reach at LHC while being consistent with lower energy phenomenology.
34406165
Standard model with compactified spatial dimensions
We analyze the structure of the standard model coupled to gravity with spatial dimensions compactified on a three-torus. We find that there are no stable one-dimensional vacua at zero temperature, although there does exist an unstable vacuum for a particular set of Dirac neutrino masses.
118501625
Standard model vacua for two-dimensional compactifications
We examine the structure of lower-dimensional standard model vacua for two-dimensional compactifications (on a 2D torus and on a 2D sphere). In the case of the torus we find a new standard model vacuum for a large range of neutrino masses consistent with experiment. Quantum effects play a crucial role in the existence of this vacuum. For the compactification on a sphere the classical terms dominate the effective potential for large radii and a stable vacuum is achieved only by introducing a large magnetic flux. We argue that there are no two-dimensional standard model vacua for compactifications on a surface of genus greater than one.