4,845 research outputs found
Interactions between Octet Baryons in the SU_6 Quark model
The baryon-baryon interactions for the complete baryon octet (B_8) are
investigated in a unified framework of the resonating-group method, in which
the spin-flavor SU_6 quark-model wave functions are employed. Model parameters
are determined to reproduce properties of the nucleon-nucleon system and the
low-energy cross section data for the hyperon-nucleon interaction. We then
proceed to explore B_8 B_8 interactions in the strangeness S=-2, -3 and -4
sectors. The S-wave phase-shift behavior and total cross sections are
systematically understood by 1) the spin-flavor SU_6 symmetry, 2) the special
role of the pion exchange, and 3) the flavor symmetry breaking.Comment: 11 pages, 6 figures, submitted to Phys. Rev. C (Rapid Communication
All-optical transport and compression of ytterbium atoms into the surface of a solid immersion lens
We present an all-optical method to load 174Yb atoms into a single layer of
an optical trap near the surface of a solid immersion lens which improves the
numerical aperture of a microscope system. Atoms are transported to a region 20
um below the surface using a system comprised by three optical dipole traps.
The "optical accordion" technique is used to create a condensate and compress
the atoms to a width of 120 nm and a distance of 1.8 um away from the surface.
Moreover, we are able to verify that after compression the condensate behaves
as a two-dimensional quantum gas.Comment: 5 pages, 5 figure
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.
Single-Particle Spin-Orbit Strengths of the Nucleon and Hyperons by SU6 Quark-Model
The quark-model hyperon-nucleon interaction suggests an important
antisymmetric spin-orbit component. It is generated from a color analogue of
the Fermi-Breit interaction dominating in the one-gluon exchange process
between quarks. We discuss the strength S_B of the single-particle spin-orbit
potential, following the Scheerbaum's prescription. Using the SU6 quark-model
baryon-baryon interaction which was recently developed by the Kyoto-Niigata
group, we calculate NN, Lambda N and Sigma N G-matrices in symmetric nuclear
matter and apply them to estimate the strength S_B. The ratio of S_B to the
nucleon strength S_N =~ -40 MeV*fm^5 is (S_Lambda)/(S_N) =~ 1/5 and
(S_Sigma)/(S_N) =~ 1/2 in the Born approximation. The G-matrix calculation of
the model FSS modifies S_Lambda to (S_Lambda)/(S_N) =~ 1/12. For S_N and
S_Sigma, the effect of the short-range correlation is comparatively weak
against meson-exchange potentials with a short-range repulsive core. The
significant reduction of the Lambda single-particle potential arises from the
combined effect of the antisymmetric LS force, the flavor-symmetry breaking
originating from the strange to up-down quark-mass difference, as well as the
effect of the short-range correlation. The density dependence of S_B is also
examined.Comment: 26 page
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