Study of the (d,2-He) Reaction at E_d = 99 MeV

This work was supported by the National Science Foundation Grants NSF PHY 78-22774 A03, NSF PHY 81-14339, and by Indiana Universit

New Experimental Limit on Photon Hidden-Sector Paraphoton Mixing

We report on the first results of a search for optical-wavelength photons mixing with hypothetical hidden-sector paraphotons in the mass range between 10^-5 and 10^-2 electron volts for a mixing parameter greater than 10^-7. This was a generation-regeneration experiment using the "light shining through a wall" technique in which regenerated photons are searched for downstream of an optical barrier that separates it from an upstream generation region. The new limits presented here are approximately three times more sensitive to this mixing than the best previous measurement. The present results indicate no evidence for photon-paraphoton mixing for the range of parameters investigated.Comment: 9 pages, 3 figure

Effective Field Theory for Layered Quantum Antiferromagnets with Non-Magnetic Impurities

We propose an effective two-dimensional quantum non-linear sigma model combined with classical percolation theory to study the magnetic properties of site diluted layered quantum antiferromagnets like La$_{2}$Cu$_{1-x}$M$_x$O$_{4}$ (M$=$Zn, Mg). We calculate the staggered magnetization at zero temperature, $M_s(x)$, the magnetic correlation length, $\xi(x,T)$, the NMR relaxation rate, $1/T_1(x,T)$, and the N\'eel temperature, $T_N(x)$, in the renormalized classical regime. Due to quantum fluctuations we find a quantum critical point (QCP) at $x_c \approx 0.305$ at lower doping than the two-dimensional percolation threshold $x_p \approx 0.41$. We compare our results with the available experimental data.Comment: Final version accepted for publication as a Rapid Communication on Physical Review B. A new discussion on the effect of disorder in layered quantum antiferromagnets is include

Additional evidence for fusion-fission in S32+24Mg reactions: Division of excitation energy and spin in the fission fragments

We have measured rays in coincidence with C12 fragments from the fission of Ni56 produced with the S32+24Mg reaction at Elab=140 MeV. These data provide insight into the fission process in this light system by giving information about the energy and spin sharing between the C12 and Ti44 fragments, and the spin alignment of the lighter, C12 fragment. The spin transfer and the nuclear temperature at scission deduced from this measurement can be related to the compound-nucleus spin and potential energy at scission. The results indicate a statistical decay process consistent with the predictions of the transition-state model employing newer estimates of the spin- and mass-asymmetry-dependent saddle-point energies and corresponding shapes. No evidence is found for the spin alignment of the C12 fragments, contrary to what might be expected for a deep-inelastic scattering origin of the fully energy damped yields

Observation of superdeformation in Hg191

The first observation of superdeformation in the mass region A190 is reported. A rotational band of twelve transitions with an average energy spacing of 37 keV, an average moment of inertia scrF(2) of 110 Latin small letter h with stroke2 MeV-1, and an average quadrupole moment of 183 e b has been observed in Hg191; this band persists at low rotational frequency. These results are in excellent agreement with a calculation that predicts an ellipsoidal axis ratio of 1.65:1 for the superdeformed shape in this nucleus

Superdeformed band in Hg192

The observation of a superdeformed band in the nucleus Hg192 is reported. The band has sixteen transitions with an average energy spacing of 36 keV and an average dynamic moment of inertia scrI(2) of 112 Latin small letter h with stroke2 MeV-1. This band persists to rather low rotational frequency (Latin small letter h with stroke0.125 MeV) and is proposed to extend in spin from 10+ to 42+. No transitions linking the superdeformed states and the low deformation yrast levels were found and the decay out of the superdeformed band appears to be statistical. This is the second case of superdeformation in the 190 region

Feeding of superdeformed bands: The mechanism and constraints on band energies and the well depth

Entry distributions leading to normal and superdeformed (SD) states in Hg192 have been measured. A model, based on Monte Carlo simulations of γ cascades, successfully reproduces the entry distribution for SD states, as well as all other known observables connected with the population of SD states. Comparison of experimental and model results, together with the measured SD entry distribution, suggest that the SD band lies 3.3-4.3 MeV above the normal yrast line when it decays around spin 10 and that the SD well depth is 3.5-4.5 MeV at spin 40