Nuclear Reactions: A Challenge for Few- and Many-Body Theory

A current interest in nuclear reactions, specifically with rare isotopes concentrates on their reaction with neutrons, in particular neutron capture. In order to facilitate reactions with neutrons one must use indirect methods using deuterons as beam or target of choice. For adding neutrons, the most common reaction is the (d,p) reaction, in which the deuteron breaks up and the neutron is captured by the nucleus. Those (d,p) reactions may be viewed as a three-body problem in a many-body context. This contribution reports on a feasibility study for describing phenomenological nucleon-nucleus optical potentials in momentum space in a separable form, so that they may be used for Faddeev calculations of (d,p) reactions.Comment: to appear in the Proceedings of HITES 2012: Conference on `Horizons of Innovative Theories, Experiments, and Supercomputing in Nuclear Physics', June 4-7, 2012, New Orleans, Louisian

Quark-Model Baryon-Baryon Interaction and its Applications to Hypernuclei

The quark-model baryon-baryon interaction fss2, proposed by the Kyoto-Niigata group, is a unified model for the complete baryon octet (B_8=N, Lambda, Sigma and Xi), which is formulated in a framework of the (3q)-(3q) resonating-group method (RGM) using the spin-flavor SU_6 quark-model wave functions and effective meson-exchange potentials at the quark level. Model parameters are determined to reproduce properties of the nucleon-nucleon system and the low-energy cross section data for the hyperon-nucleon scattering. Due to the several improvements including the introduction of vector-meson exchange potentials, fss2 has achieved very accurate description of the NN and YN interactions, comparable to various one-boson exchange potentials. We review the essential features of fss2 and our previous model FSS, and their predictions to few-body systems in confrontation with the available experimental data. Some characteristic features of the B_8 B_8 interactions with the higher strangeness, S=-2, -3, -4, predicted by fss2 are discussed. These quark-model interactions are now applied to realistic calculations of few-body systems in a new three-cluster Faddeev formalism which uses two-cluster RGM kernels. As for the few-body systems, we discuss the three-nucleon bound states, the Lambda NN-Sigma NN system for the hypertriton, the alpha alpha Lambda system for 9Be Lambda, and the Lambda Lambda alpha system for 6He Lambda Lambda.Comment: 20 pages, 12 figures, 18th Nishinomiya Yukawa Memorial Symposium on Strangeness in Nuclear Matter, 4 - 5 December 2003, Nishinomiya, Japan. (to be published in Prog. Theor. Phys. Suppl.

Electromagnetic K+ production on the deuteron with hyperon recoil polarization

Photo- and electroproduction processes of K+ on the deuteron are investigated theoretically. Modern hyperon-nucleon forces as well as an updated kaon production operator on the nucleon are used. Sizable effects of the hyperon-nucleon final state interaction are seen in various observables. Especially the photoproduction double polarization observable C_z is shown to provide a handle to distinguish different hyperon-nucleon force models.Comment: 4 pages, 7 eps-figures, talk given at the VII International Conference on Hypernuclear and Strange Particle Physics, Torino, Italy, October 23-27, 2000, to appear in the proceedings (Nucl. Phys. A

NMR Evidence for Antiferromagnetic Transition in the Single-Component Molecular System, [Cu(tmdt)2_{2}]

The magnetic state of the single-component molecular compound, [Cu(tmdt)$_{2}$], is investigated by means of $^{1}$H-NMR. An abrupt spectral broadening below 13 K and a sharp peak in nuclear spin-lattice relaxation rate, $T_{1}^{-1}$, at 13 K are observed as clear manifestations of a second-order antiferromagnetic transition, which is consistent with the previously reported magnetic susceptibility and EPR measurement. The ordered moment is estimated at $0.22-0.45$ ${\mu}_{\rm B}$/molecule. The temperature-dependence of $T_{1}^{-1}$ above the transition temperature indicates one-dimensional spin dynamics and supports that the spins are on the central part of the molecule differently from other isostructural compounds.Comment: 13pages, 5 figure

Electron Correlations in the Quasi-Two-Dimensional Organic Conductor θ\theta-(BEDT-TTF)2_{2}I3_{3} investigated by 13^{13}C NMR

We report a $^{13}$C-NMR study on the ambient-pressure metallic phase of the layered organic conductor $\theta$-(BEDT-TTF)$_{2}$I$_{3}$ [BEDT-TTF: bisethylenedithio-tetrathiafulvalene], which is expected to connect the physics of correlated electrons and Dirac electrons under pressure. The orientation dependence of the NMR spectra shows that all BEDT-TTF molecules in the unit cell are to be seen equivalent from a microscopic point of view. This feature is consistent with the orthorhombic symmetry of the BEDT-TTF sublattice and also indicates that the monoclinic $I_{3}$ sublattice, which should make three molecules in the unit cell nonequivalent, is not practically influential on the electronic state in the conducting BEDT-TTF layers at ambient pressure. There is no signature of charge disproportionation in opposition to most of the $\theta$-type BEDT-TTF salts. The analyses of NMR Knight shift, $K$, and the nuclear spin-lattice relaxation rate, $1/T_{1}$, revealed that the degree of electron correlation, evaluated by the Korringa ratio [$\varpropto 1/(T_{1}TK^{2}$)], is in an intermediate regime. However, NMR relaxation rate $1/T_{1}$ is enhanced above $\sim$ 200K, which possibly indicates that the system enters into a quantum critical regime of charge-order fluctuations as suggested theoretically.Comment: 19pages, 6figure

Lambda-N scattering length from the reaction gamma d -> K^+ Lambda n

The perspects of utilizing the strangeness-production reaction gamma d -> K^+ Lambda n for the determination of the Lambda n low-energy scattering parameters are investigated. The spin observables that need to be measured in order to isolate the Lambda n singlet (1S0) and triplet (3S1) states are identified. Possible kinematical regions where the extraction of the Lambda n scattering lengths might be feasible are discussed.Comment: 8 pages, 4 figure