Addendum: Triton and hypertriton binding energies calculated from SU_6 quark-model baryon-baryon interactions

Previously we calculated the binding energies of the triton and hypertriton, using an SU_6 quark-model interaction derived from a resonating-group method of two baryon clusters. In contrast to the previous calculations employing the energy-dependent interaction kernel, we present new results using a renormalized interaction, which is now energy independent and reserves all the two-baryon data. The new binding energies are slightly smaller than the previous values. In particular the triton binding energy turns out to be 8.14 MeV with a charge-dependence correction of the two-nucleon force, 190 keV, being included. This indicates that about 350 keV is left for the energy which is to be accounted for by three-body forces.Comment: 4 pages, 1 figur

FE analysis on tube hydroforming of small diametr ZM21 magnesium alloy tube

Tube hydroforming (THF) is one of the plasticity processing methods. Tubular parts, for instance automotive components are expanded by forces such as internal pressure and axial compression in order to deform an objective shape. THF has less restriction on shape and size of workpieces owing to adopting the liquid tool. The demand of a small diameter magnesium alloy tubular parts have been increased for applying small medical and electronic devices. In this study, it was investigated that influence of process conditions such as processing temperature, internal pressure and axial feeding amount on formability of small diameter ZM21 magnesium alloy tube with outer diameter of 2.0mm and thickness of 0.20mm. Furthermore, the processing conditions for improving the formability of material in THF were examined. For prior evaluation of deformation characteristics in the warm THF of small diameter ZM21 magnesium alloy tube, a finite element (FE) simulation was conducted. The FE method (FEM) code was used LS-DYNA 3D for analysis of the FE model of the tube and the dies. The material characteristics were obtained by tensile test and fracture test. From FE analysis results, it was elucidated that effect of the processing temperature, the variable internal pressure and the axial feeding amount on deformation behavior. The formability of ZM21 magnesium alloy tube was improved by processing at 250 C. The difference of deformation characteristic between FE results and experimental results was compared. As the results, the processing condition which could improve the formability of ZM21 tube was clarified using this FE model. The effect of adding the straightening stage in the loading path after the preform on formability was investigated. The thinning of the wall thickness of the tube was inhibited by calibration after the axial feeding

Inclusive K+K^+ and exclusive K+YK^+Y photoproduction on the deuteron: Λ\Lambda- and Σ\Sigma-threshold phenomena

Inclusive $K^+$ and exclusive $K^+Y$ photoproduction on the deuteron are investigated theoretically. Modern hyperon-nucleon forces and a recently updated kaon photoproduction operator for the $\gamma +N\to K^++Y$ process are used. Sizable effects of the hyperon-nucleon final state interaction are found near the $K^+\Lambda N$ and $K^+\Sigma N$ thresholds in the inclusive reaction. Angular distributions for the exclusive process show clear $YN$ final state interaction effects in certain kinematic regions. Precise data especially for the inclusive process around the $K^+\Sigma N$ threshold would help to clarify the strength and property of the $\Lambda N-\Sigma N$ interaction.Comment: 14 pages, 10 figure

Excitation spectra of the spin-1/2 triangular-lattice Heisenberg antiferromagnet

We use series expansion methods to calculate the dispersion relation of the one-magnon excitations for the spin-1/2 triangular-lattice nearest-neighbor Heisenberg antiferromagnet above a three-sublattice ordered ground state. Several striking features are observed compared to the classical (large-S) spin-wave spectra. Whereas at low energies the dispersion is only weakly renormalized by quantum fluctuations, significant anomalies are observed at high energies. In particular, we find roton-like minima at special wave-vectors and strong downward renormalization in large parts of the Brillouin zone, leading to very flat or dispersionless modes. We present detailed comparison of our calculated excitation energies in the Brillouin zone with the spin-wave dispersion to order 1/S calculated recently by Starykh, Chubukov, and Abanov [cond-mat/0608002]. We find many common features but also some quantitative and qualitative differences. We show that at temperatures as low as 0.1J the thermally excited rotons make a significant contribution to the entropy. Consequently, unlike for the square lattice model, a non-linear sigma model description of the finite-temperature properties is only applicable at extremely low temperatures.Comment: 14 pages, 11 figure

The nonmesonic weak decay of the hypertriton

The nonmesonic decay of the hypertriton is calculated based on a hypertriton wavefunction and 3N scattering states, which are rigorous solutions of 3-body Faddeev equations using realistic NN and hyperon-nucleon interactions. The pion-exchange together with heavier meson exchanges for the $\Lambda N \to N N$ transition is considered. The total nonmesonic decay rate is found to be 0.5% of the free $\Lambda$ decay rate. Integrated as well as differential decay rates are given. The p- and n- induced decays are discussed thoroughly and it is shown that the corresponding total rates cannot be measured individually.Comment: 27 pages, 20 figures, revtex, submitted to Phys. Rev.

Direct evidence for ferromagnetic spin polarization in gold nanoparticles

We report the first direct observation of ferromagnetic spin polarization of Au nanoparticles with a mean diameter of 1.9 nm using X-ray magnetic circular dichroism (XMCD). Owing to the element selectivity of XMCD, only the gold magnetization is explored. Magnetization of gold atoms estimated by XMCD shows a good agreement with the results obtained by conventional magnetometry. This result is evidence of intrinsic spin polarization in nano-sized gold.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

Precise calculation of the two-step process for K- d -> pi Sigma N in the Lambda (1405) resonance region

The reaction K- d -> pi Sigma N is investigated taking into account single scattering and the two-step process due to Kbar N -> pi Sigma rescattering. The influence of some common approximations are examined. It is found that the treatment of the kinematics in the Green's function that appears in the loop integral of the rescattering process has a rather strong impact on the resulting lineshape of the pi Sigma invariant mass spectrum. Specifically, a calculation with correct kinematics where the three-body unitarity cut due to the nK- p threshold occurs at the physical value yields a pronounced peak in the invariant mass spectrum at this threshold and, at the same time, suppresses the signal in the region of the Lambda(1405) resonance. On the other hand, an approximation applied in past calculations shifts that threshold down and, consequently, leads to an accidental and therefore erroneous enhancement of the signal of the Lambda(1405) in the pi Sigma invariant mass spectrum.Comment: 11 pages, 13 figure