385 research outputs found
Faddeev calculation of a quasi-bound state
We report on the first genuinely three-body
coupled-channel Faddeev calculation in search for quasi-bound states in the
system. The main absorptivity in the subsystem is accounted
for by fitting to data near threshold. Our calculation yields one such
quasi-bound state, with , , bound in the range MeV, with a width of MeV. These results differ
substantially from previous estimates, and are at odds with the signal observed by the FINUDA collaboration.Comment: Minor editorial revision; version accepted for publication in Phys.
Rev. Let
Ab initio approach to s-shell hypernuclei 3H_Lambda, 4H_Lambda, 4He_Lambda and 5He_Lambda with a Lambda N-Sigma N interaction
Variational calculations for s-shell hypernuclei are performed by explicitly
including degrees of freedom. Four sets of YN interactions (SC97d(S),
SC97e(S), SC97f(S) and SC89(S)) are used. The bound-state solution of
He is obtained and a large energy expectation value of the tensor
transition part is found. The internal energy of the
He subsystem is strongly affected by the presence of a particle
with the strong tensor transition potential.Comment: Phys. Rev. Lett. 89, 142504 (2002
The (K-,p) reaction on nuclei with in-flight kaons
We perform a theoretical study of the spectrum of protons with kinetic
energies of around 600 MeV, emitted following the interaction of 1 GeV/c kaons
with nuclei. A recent experimental analysis of this (K-,p) reaction on 12C,
based on the dominant quasielastic process, has suggested a deeply attractive
kaon nucleus potential. Our Monte Carlo simulation considers, in addition, the
one-and two-nucleon K- absorption processes producing hyperons that decay into
\pi N pairs. We find that this kaon in-flight reaction is not well suited to
determine the kaon optical potential due, essentially, to the limited
sensitivity of the cross section to its strength, but also to unavoidable
uncertainties from the coincidence requirement applied in the experiment. A
shallow kaon nucleus optical potential obtained in chiral models is perfectly
compatible with the observed spectrum.Comment: To appear in the proceedings of the 10th International Conference on
Hypernuclear and Strange Particle Physics, Tokai, Ibaraki (Japan), 14-18
September, 200
quasi-bound state and the interaction: coupled-channel Faddeev calculations of the system
Coupled-channel three-body calculations of an ,
quasi-bound state in the system were
performed and the dependence of the resulting three-body energy on the two-body
interaction was investigated. Earlier results of
binding energy MeV and width
MeV are confirmed [N.V. Shevchenko {\it et al.}, Phys. Rev. Lett. {\bf 98},
082301 (2007)]. It is shown that a suitably constructed energy-independent
complex potential gives a considerably shallower and narrower
three-body quasi-bound state than the full coupled-channel calculation.
Comparison with other calculations is made.Comment: 22 pages, 7 figures, 4 tables; minor corrections, accepted for
publication in Phys. Rev.
nuclear bound states in a dynamical model
A comprehensive data base of K- atom level shifts and widths is re-analyzed
in order to study the density dependence of the Kbar-nuclear optical potential.
Significant departure from a t*rho form is found only for nuclear densities
about and less than 20% of nuclear-matter density, and extrapolation to
nuclear-matter density yields an attractive potential, about 170 MeV deep.
Partial restoration of chiral symmetry compatible with pionic atoms and
low-energy pion-nuclear data plays no role at the relevant low-density regime,
but this effect is not ruled out at high densities. Kbar-nuclear bound states
are generated across the periodic table self consistently, using a relativistic
mean-field model Lagrangian which couples the Kbar to the scalar and vector
meson fields mediating the nuclear interactions. The reduced phase space
available for Kbar absorption from these bound states is taken into account by
adding an energy-dependent imaginary term which underlies the corresponding
Kbar-nuclear level widths, with a strength required by fits to the atomic data.
Substantial polarization of the core nucleus is found for light nuclei, and the
binding energies and widths calculated in this dynamical model differ
appreciably from those calculated for a static nucleus. A wide range of binding
energies is spanned by varying the Kbar couplings to the meson fields. Our
calculations provide a lower limit of Gamma(Kbar) = 50 +/- 10 MeV on the width
of nuclear bound states for Kbar binding energy in the range B(Kbar) = 100 -
200 MeV. Comments are made on the interpretation of the FINUDA experiment at
DAFNE, Frascati, which claimed evidence for deeply bound (K- pp) states in
light nuclei.Comment: Added 2 figures and discussion. Version accepted for publication in
NP
Characterizing Interdisciplinarity of Researchers and Research Topics Using Web Search Engines
Researchers' networks have been subject to active modeling and analysis.
Earlier literature mostly focused on citation or co-authorship networks
reconstructed from annotated scientific publication databases, which have
several limitations. Recently, general-purpose web search engines have also
been utilized to collect information about social networks. Here we
reconstructed, using web search engines, a network representing the relatedness
of researchers to their peers as well as to various research topics.
Relatedness between researchers and research topics was characterized by
visibility boost-increase of a researcher's visibility by focusing on a
particular topic. It was observed that researchers who had high visibility
boosts by the same research topic tended to be close to each other in their
network. We calculated correlations between visibility boosts by research
topics and researchers' interdisciplinarity at individual level (diversity of
topics related to the researcher) and at social level (his/her centrality in
the researchers' network). We found that visibility boosts by certain research
topics were positively correlated with researchers' individual-level
interdisciplinarity despite their negative correlations with the general
popularity of researchers. It was also found that visibility boosts by
network-related topics had positive correlations with researchers' social-level
interdisciplinarity. Research topics' correlations with researchers'
individual- and social-level interdisciplinarities were found to be nearly
independent from each other. These findings suggest that the notion of
"interdisciplinarity" of a researcher should be understood as a
multi-dimensional concept that should be evaluated using multiple assessment
means.Comment: 20 pages, 7 figures. Accepted for publication in PLoS On
On kaonic hydrogen. Phenomenological quantum field theoretic model revisited
We argue that due to isospin and U-spin invariance of strong low-energy
interactions the S-wave scattering lengths a^0_0 and a^1_0 of bar-KN scattering
with isospin I=0 and I = 1 satisfy the low-energy theorem a^0_0 + 3 a^1_0 = 0
valid to leading order in chiral expansion. In the model of strong low-energy
bar-KN interactions at threshold (EPJA 21,11 (2004)) we revisit the
contribution of the Sigma(1750) resonance, which does not saturate the
low-energy theorem a^0_0 + 3 a^1_0 = 0, and replace it by the baryon background
with properties of an SU(3) octet. We calculate the S-wave scattering
amplitudes of K^-N and K^-d scattering at threshold. We calculate the energy
level displacements of the ground states of kaonic hydrogen and kaonic
deuterium. The result obtained for kaonic hydrogen agrees well with recent
experimental data by the DEAR Collaboration. We analyse the cross sections for
elastic and inelastic K^-p scattering for laboratory momenta of the incident
K^- meson from the domain 70 MeV/c < p_K < 150 MeV/c. The theoretical results
agree with the available experimental data within two standard deviations.Comment: 20 pages, Latex, We have slightly corrected the contribution of the
double scattering. This changes the S-wave scattering length of K^-d
scattering by 17%, which is commensurable with the theoretical uncertaint
Plans for Hadronic Structure Studies at J-PARC
Hadron-physics projects at J-PARC are explained. The J-PARC is the
most-intense hadron-beam facility in the multi-GeV high-energy region. By using
secondary beams of kaons, pions, and others as well as the primary-beam proton,
various hadron projects are planned. First, some of approved experiments are
introduced on strangeness hadron physics and hadron-mass modifications in
nuclear medium. Second, future possibilities are discussed on hadron-structure
physics, including structure functions of hadrons, spin physics, and
high-energy hadron reactions in nuclear medium. The second part is discussed in
more details because this is an article in the hadron-structure session.Comment: 10 pages, LaTeX, 20 eps files, to be published in Journal of Physics:
Conference Series (JPCS), Proceedings of the 24th International Nuclear
Physics Conference (INPC 2010), Vancouver, Canada, July 4 - 9, 201
Signature of strange dibaryon in kaon-induced reaction
We examine how the signature of the strange-dibaryon resonances in the
barKNN-piSigmaN system shows up in the scattering amplitude on the physical
real energy axis within the framework of Alt-Grassberger-Sandhas (AGS)
equations. The so-called point method is applied to handle the three-body
unitarity cut in the amplitudes. We also discuss the possibility that the
strange-dibaryon production reactions can be used for discriminating between
existing models of the two-body barKN-piSigma system with Lambda(1405).Comment: 4 pages, 6 figures, talk given at The Fifth Asia-Pacific Conference
on Few-Body Problems in Physics 2011 (APFB2011), held in Seoul, Korea, August
22-26, 201
Realistic shell-model calculations: current status and open problems
The main steps involved in realistic shell-model calculations employing
two-body low-momentum interactions are briefly reviewed. The practical value of
this approach is exemplified by the results of recent calculations and some
remaining open questions and directions for future research are discussed.Comment: 12 pages, 2 figures, contribution to J. Phys G, Special Issue, Focus
Section: Open Problems in Nuclear Structur
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