Faddeev calculation of a K−ppK^- p p quasi-bound state

We report on the first genuinely three-body ${\bar K}NN - \pi \Sigma N$ coupled-channel Faddeev calculation in search for quasi-bound states in the $K^- p p$ system. The main absorptivity in the $K^- p$ subsystem is accounted for by fitting to $K^- p$ data near threshold. Our calculation yields one such quasi-bound state, with $I=1/2$, $J^{\pi}=0^-$, bound in the range $B \sim 55-70$ MeV, with a width of $\Gamma \sim 95-110$ MeV. These results differ substantially from previous estimates, and are at odds with the $K^- p p \to \Lambda p$ 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 $\Sigma$ degrees of freedom. Four sets of YN interactions (SC97d(S), SC97e(S), SC97f(S) and SC89(S)) are used. The bound-state solution of $_\Lambda^5$He is obtained and a large energy expectation value of the tensor $\Lambda N-\Sigma N$ transition part is found. The internal energy of the $^4$He subsystem is strongly affected by the presence of a $\Lambda$ particle with the strong tensor $\Lambda N-\Sigma N$ 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

KˉNN\bar{K}NN quasi-bound state and the KˉN\bar{K}N interaction: coupled-channel Faddeev calculations of the KˉNN−πΣN\bar{K}NN - \pi \Sigma N system

Coupled-channel three-body calculations of an $I=1/2$, $J^{\pi}=0^-$ $\bar{K}NN$ quasi-bound state in the $\bar{K}NN - \pi \Sigma N$ system were performed and the dependence of the resulting three-body energy on the two-body $\bar{K}N - \pi \Sigma$ interaction was investigated. Earlier results of binding energy $B_{K^-pp} \sim 50 -70$ MeV and width $\Gamma_{K^-pp} \sim 100$ 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 $\bar{K}N$ 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.

Kˉ\bar K 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

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

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