Neutron and Proton Transverse Emission Ratio Measurements and the Density Dependence of the Asymmetry Term of the Nuclear Equation of State

Recent measurements of pre-equilibrium neutron and proton transverse emission from (112,124)Sn+(112,124)Sn reactions at 50 MeV/A have been completed at the National Superconducting Cyclotron Laboratory. Free nucleon transverse emission ratios are compared to those of A=3 mirror nuclei. Comparisons are made to BUU transport calculations and conclusions concerning the density dependence of the asymmetry term of the nuclear equation-of-state at sub-nuclear densities are made. The double-ratio of neutron-proton ratios between two reactions is employed as a means of reducing first-order Coulomb effects and detector efficiency effects. Comparison to BUU model predictions indicate a density dependence of the asymmetry energy that is closer to a form in which the asymmety energy increases as the square root of the density for the density region studied. A coalescent-invariant analysis is introduced as a means of reducing suggested difficulties with cluster emission in total nucleon emission. Future experimentation is presented

Prompt Alpha Decay of a Well-deformed Band in 58Ni

Two excited well-deformed bands have been observed in the semi-magic nucleus Ni-58. One of the bands was observed to partially decay by emission of a prompt discrete alpha particle that feeds the 2949 keV 6(+) spherical yrast state in the daughter nucleus Fe-54. This constitutes the first observation of prompt alpha emission from states lying in the deformed secondary minimum of the nuclear potential. gamma -ray linking transitions via several parallel paths establish the spin. parity, and excitation energy of this deformed band in Ni-58

Prompt Alpha Decay of a Well-deformed Band in 58Ni

Two excited well-deformed bands have been observed in the semi-magic nucleus Ni-58. One of the bands was observed to partially decay by emission of a prompt discrete alpha particle that feeds the 2949 keV 6(+) spherical yrast state in the daughter nucleus Fe-54. This constitutes the first observation of prompt alpha emission from states lying in the deformed secondary minimum of the nuclear potential. gamma -ray linking transitions via several parallel paths establish the spin. parity, and excitation energy of this deformed band in Ni-58

Evidence for Shape Co-existence at medium spin in 76Rb

Four previously known rotational bands in 76Rb have been extended to moderate spins using the Gammasphere and Microball gamma ray and charged particle detector arrays and the 40Ca(40Ca,3pn) reaction at a beam energy of 165 MeV. The properties of two of the negative-parity bands can only readily be interpreted in terms of the highly successful Cranked Nilsson-Strutinsky model calculations if they have the same configuration in terms of the number of g9/2 particles, but they result from different nuclear shapes (one near-oblate and the other near-prolate). These data appear to constitute a unique example of shape co-existing structures at medium spins.Comment: Accepted for publication in Physics Letters

Orbifold projection in supersymmetric QCD at N_f\leq N_c

Supersymmetric orbifold projection of N=1 SQCD with relatively small number of flavors (not larger than the number of colors) is considered. The purpose is to check whether orbifolding commutes with the infrared limit. On the one hand, one considers the orbifold projection of SQCD and obtains the low-energy description of the resulting theory. On the other hand, one starts with the low-energy effective theory of the original SQCD, and only then perfoms orbifolding. It is shown that at finite N_c the two low-energy theories obtained in these ways are different. However, in the case of stabilized run-away vacuum these two theories are shown to coincide in the large N_c limit. In the case of quantum modified moduli space, topological solitons carrying baryonic charges are present in the orbifolded low-energy theory. These solitons may restore the correspondence between the two theories provided that the soliton mass tends to zero in the large N_c limit.Comment: 10 pages; misprint corrected, reference adde

High-spin transition quadrupole moments in neutron-rich Mo and Ru nuclei: testing γ\gamma softness?

The transition quadrupole moments, $Q_{t}$, of rotational bands in the neutron-rich, even-mass $^{102-108}$Mo and $^{108-112}$Ru nuclei were measured in the 8 to 16 $\hbar$ spin range with the Doppler-shift attenuation method. The nuclei were populated as fission fragments from $^{252}$Cf fission. The detector setup consisted of the Gammasphere spectrometer and the HERCULES fast-plastic array. At moderate spin, the $Q_{t}$ moments are found to be reduced with respect to the values near the ground states. Attempts to describe the observations in mean-field-based models, specifically cranked relativistic Hartree-Bogoliubov theory, illustrate the challenge theory faces and the difficulty to infer information on $\gamma$ softness and triaxiality from the data.Comment: 17 pages, 4 figure

Shape coexistence and disappearance of pairing correlations in 82Sr

Extensive high-spin band structures in 82Sr have been established using proton-[gamma]-[gamma] coincidence techniques. On the basis of the Woods-Saxon cranking calculations with pairing, four of these bands are interpreted to have prolate, oblate, or triaxial shapes. Pairing correlations are predicted to be very weak at high spins in this nucleus, and calculations with no static pairing successfully reproduce the experimentally observed crossing frequencies and alignments despite the fact that none of the bands displays a rigid-rotor behavior. It is concluded that observation of rigid-rotor behavior is neither necessary nor sufficient for the disappearance of static pairing in nuclei.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29458/1/0000540.pd