Electric dipole response of 6^6He: Halo-neutron and core excitations

Electric dipole ($E1$) response of $^{6}$He is studied with a fully microscopic six-body calculation. The wave functions for the ground and excited states are expressed as a superposition of explicitly correlated Gaussians (CG). Final state interactions of three-body decay channels are explicitly taken into account. The ground state properties and the low-energy $E1$ strength are obtained consistently with observations. Two main peaks as well as several small peaks are found in the $E1$ strength function. The peak at the high-energy region indicates a typical macroscopic picture of the giant dipole resonance, the out-of-phase proton-neutron motion. The transition densities of the lower-lying peaks exhibit in-phase proton-neutron motion in the internal region, out-of-phase motion near the surface region, and spatially extended neutron oscillation, indicating a soft-dipole mode (SDM) and its vibrationally excited mode.Comment: 12 pages, 12 figures, to appear in Phys. Rev.

Universal four-body states in heavy-light mixtures with positive scattering length

The number of four-body states known to behave universally is small. This work adds a new class of four-body states to this relatively short list. We predict the existence of a universal four-body bound state for heavy-light mixtures consisting of three identical heavy fermions and a fourth distinguishable lighter particle with mass ratio $\kappa \gtrsim 9.5$ and short-range interspecies interaction characterized by a positive s-wave scattering length. The structural properties of these universal states are discussed and finite-range effects are analyzed. The bound states can be experimentally realized and probed utilizing ultracold atom mixtures.Comment: 5 page

Inelastic final-state interaction

The final-state interaction in multichannel decay processes is sytematically studied with application to B decay in mind. Since the final-state inteaction is intrinsically interwoven with the decay interaction in this case, no simple phase theorem like "Watson's theorem" holds for experimentally observed final states. We first examine in detail the two-channel problem as a toy-model to clarify the issues and to remedy common mistakes made in earlier literature. Realistic multichannel problems are too challenging for quantitative analysis. To cope with mathematical complexity, we introduce a method of approximation that is applicable to the case where one prominant inelastic channel dominates over all others. We illustrate this approximation method in the amplitude of the decay B to pi K fed by the intermediate states of a charmed meson pair. Even with our approximation we need more accurate information of strong interactions than we have now. Nonethless we are able to obtain some insight in the issue and draw useful conclusions on general fearyres on the strong phases.Comment: The published version. One figure correcte

Towards pp -> VVjj at NLO QCD: Bosonic contributions to triple vector boson production plus jet

In this work, some of the NLO QCD corrections for pp -> VVjj + X are presented. A program in Mathematica based on the structure of FeynCalc which automatically simplifies a set of amplitudes up to the hexagon level of rank 5 has been created for this purpose. We focus on two different topologies. The first involves all the virtual contributions needed for quadruple electroweak vector boson production, i.e. pp -> VVVV + X. In the second, the remaining "bosonic" corrections to electroweak triple vector boson production with an additional jet (pp -> VVV j + X) are computed. We show the factorization formula of the infrared divergences of the bosonic contributions for VVVV and VVVj production with V=(W,Z,gamma). Stability issues associated with the evaluation of the hexagons up to rank 5 are studied. The CPU time of the FORTRAN subroutines rounds the 2 milliseconds and seems to be competitive with other more sophisticated methods. Additionally, in Appendix A the master equations to obtain the tensor coefficients up to the hexagon level in the external momenta convention are presented including the ones needed for small Gram determinants.Comment: 48 pages,16 figure

The Gamow-Teller States in Relativistic Nuclear Models

The Gamow-Teller(GT) states are investigated in relativistic models. The Landau-Migdal(LM) parameter is introduced in the Lagrangian as a contact term with the pseudo-vector coupling. In the relativistic model the total GT strength in the nucleon space is quenched by about 12% in nuclear matter and by about 6% in finite nuclei, compared with the one of the Ikeda-Fujii-Fujita sum rule. The quenched amount is taken by nucleon-antinucleon excitations in the time-like region. Because of the quenching, the relativistic model requires a larger value of the LM parameter than non-relativistic models in describing the excitation energy of the GT state. The Pauli blocking terms are not important for the description of the GT states.Comment: REVTeX4, no figure

Measurement of mutual inductance from frequency dependence of impedance of AC coupled circuit using digital dual-phase lock-in amplifier

We present a simple method to determine the mutual inductance $M$ between two coils in a coupled AC circuit by using a digital dual-phase lock-in amplifier. The frequency dependence of the real and imaginary parts is measured as the coupling constant is changed. The mutual inductance $M$ decreases as the distance $d$ between the centers of coils is increased. We show that the coupling constant is proportional to $d^{-n}$ with an exponent $n$ ($\approx$ 3). This coupling is similar to that of two magnetic moments coupled through a dipole-dipole interaction.Comment: 9 pages, 10 figures, Fig.1 is corrected, figures in png files, short version is published in Am. J. Phys. 76, (2008) 12