5,015 research outputs found
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.
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
Three-Cluster Equation Using Two-Cluster RGM Kernel
We propose a new type of three-cluster equation which uses two-cluster
resonating-group-method (RGM) kernels. In this equation, the orthogonality of
the total wave-function to two-cluster Pauli-forbidden states is essential to
eliminate redundant components admixed in the three-cluster systems. The
explicit energy-dependence inherent in the exchange RGM kernel is
self-consistently determined. For bound-state problems, this equation is
straightforwardly transformed to the Faddeev equation which uses a modified
singularity-free T-matrix constructed from the two-cluster RGM kernel. The
approximation of the present three-cluster formalism can be examined with more
complete calculation using the three-cluster RGM. As a simple example, we
discuss three di-neutron (3d') and 3 alpha systems in the harmonic-oscillator
variational calculation. The result of the Faddeev calculation is also
presented for the 3' system.Comment: 12 pages, no figur
Emergence of inhomogeneous moments from spin liquid in the triangular-lattice Mott insulator -(ET)Cu(CN)
The static and dynamic local spin susceptibility of the organic Mott
insulator -(ET)Cu(CN), a model material of the spin- 1/2
triangular lattice, is studied by C NMR spectroscopy from room
temperature down to 20 mK. We observe an anomalous field-dependent spectral
broadening with the continuous and bipolar shift distribution, appearing
without the critical spin fluctuations. It is attributable to spatially
nonuniform magnetizations induced in the spin liquid under magnetic fields. The
amplitude of the magnetization levels off below 1 K, while the low-lying spin
fluctuations survive toward the ground state, as indicated by the temperature
profile of the relaxation rates.Comment: 4 pages, 4 figure
Contributions of -exchange, -exchange, and contact three-body forces in NNLO ChEFT to H
Faddeev calculations of hypertriton (H) separation energy are
performed, incorporating all next-to-next-to-leading-order NN
three-body forces (3BFs) in chiral effective field theory: -exchange,
-exchange, and contact interactions. The -exchange and contact
interactions are rewritten in a form suitable for evaluating partial-wave
matrix elements. The -deuteron folding potentials constructed from
these 3BFs are evaluated to demonstrate their contributions to \h3t. The
-exchange interaction provides an attractive effect in which the d-state
component of the deuteron wave function plays an important role. The attractive
contribution tends to cancel the repulsive ones from the -exchange and
contact 3BFs. Faddeev calculations show that the net effect of the 3BFs to the
\h3t separation energy is small in a range between to keV, depending
on the NN interaction used. Although these results are based on speculative
low-energy constants, they can serve as a reference for further investigations.Comment: 6 pages, 4 figure
Faddeev Calculation of H Incorporating 2{\pi} Exchange NN Interaction
Faddeev calculations of hypertriton (H) separation energy are
performed, incorporating -exchange NN three-baryon force.
Repulsive contributions of the three-baryon force in the order of 50 100
keV are found, depending on the NN interactions employed. The effect is not
negligible compared with the small separation-energy of H and is
essential to gauge the two-body N interactions.Comment: 6 pages, 3 Figure
Partial-wave expansion of three-baryon interactions in chiral effective field theory
An expression of partial wave expansion of three-baryon interactions in
chiral effective field theory is presented. The derivation follows the method
by Hebeler et al. [Phys. Rev. C{\bf 91}, 044001 (2015)], but the final
expression is more general. That is, a systematic treatment of the higher-rank
spin-momentum structure of the interaction becomes possible. Using the derived
formula, a -deuteron folding potential is evaluated. This information
is valuable for inferring the possible contribution of the
three-baryon forces to the hypertriton as the basis of further studies by
sophisticated Faddeev calculations. A microscopic understanding of
three-baryon forces together with two-body interactions is
essential for the description of hypernuclei and neutron-star matter.Comment: 7 pages, 4 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 transition is considered. The total nonmesonic decay rate is found to be 0.5%
of the free 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.
Anisotropic charge dynamics in the quantum spin-liquid candidate -(BEDT-TTF)Cu(CN)
We have in detail characterized the anisotropic charge response of the dimer
Mott insulator -(BEDT-TTF)\-Cu(CN) by dc conductivity, Hall
effect and dielectric spectroscopy. At room temperature the Hall coefficient is
positive and close to the value expected from stoichiometry; the temperature
behavior follows the dc resistivity . Within the planes the dc
conductivity is well described by variable-range hopping in two dimensions;
this model, however, fails for the out-of-plane direction. An unusually broad
in-plane dielectric relaxation is detected below about 60 K; it slows down much
faster than the dc conductivity following an Arrhenius law. At around 17 K we
can identify a pronounced dielectric anomaly concomitantly with anomalous
features in the mean relaxation time and spectral broadening. The out-of-plane
relaxation, on the other hand, shows a much weaker dielectric anomaly; it
closely follows the temperature behavior of the respective dc resistivity. At
lower temperatures, the dielectric constant becomes smaller both within and
perpendicular to the planes; also the relaxation levels off. The observed
behavior bears features of relaxor-like ferroelectricity. Because
heterogeneities impede its long-range development, only a weak tunneling-like
dynamics persists at low temperatures. We suggest that the random potential and
domain structure gradually emerge due to the coupling to the anion network.Comment: 14 pages, 13 figure
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