Hyperonic mixing in five-baryon double-strangeness hypernuclei in a two-channel treatment

Properties of hypernuclei $_{\Lambda \Lambda}^5$H and $_{\Lambda \Lambda }^5$He are studied in a two-channel approach with explicit treatment of coupling of channels ^3\text{Z}+\Lambda+\Lambda and \alpha+\Xi. Diagonal \Lambda\Lambda and coupling \Lambda\Lambda-\Xi N interactions are derived within G-matrix procedure from Nijmegen meson-exchange models. Bond energy \Delta B_{\Lambda\Lambda} in $_{\Lambda \Lambda}^5$He exceeds significantly that in $_{\Lambda \Lambda}^5$H due to the channel coupling. Diagonal \Xi\alpha attraction amplifies the effect, which is sensitive also to \Lambda-core interaction. The difference of the \Delta B_{\Lambda\Lambda} values can be an unambiguous signature of the \Lambda\Lambda-\Xi N coupling in \Lambda\Lambda hypernuclei. However, improved knowledge of the hyperon-nucleus potentials is needed for quantitative extraction of the coupling strength from future data on the \Lambda\Lambda hypernuclear binding energies.Comment: 11 pages with 3 figures; Phys. Rev. C, accepte

Consistency of Lambda-Lambda hypernuclear events

Highlights of Lambda-Lambda emulsion events are briefly reviewed. Given three accepted events, shell-model predictions based on p-shell Lambda hypernuclear spectroscopic studies are shown to reproduce the Lambda-Lambda (LL) binding energies of LL10Be and LL13B in terms of the LL binding energy of LL6He. Predictions for other species offer judgement on several alternative assignments of the LL13B KEK-E176 event, and on the assignments LL11Be and LL12Be suggested recently for the KEK-E373 HIDA event. The predictions of the shell model, spanning a wide range of A values, are compared with those of cluster models, where the latter are available.Comment: Based on talk given by Avraham Gal at EXA 2011, Vienna, September 2011; Proceedings version prepared for the journal Hyperfine Interactions; v2--slight changes, matches published versio

S-wave Pairing of Λ\Lambda Hyperons in Dense Matter

In this work we calculate the $^1S_0$ gap energies of $\Lambda$ hyperons in neutron star matter. The calculation is based on a solution of the BCS gap equation for an effective G-matrix parameterization of the $\Lambda-\Lambda$ interaction with a nuclear matter background, presented recently by Lanskoy and Yamamoto. We find that a gap energy of a few tenths of MeV is expected for $\Lambda$ Fermi momenta up to about 1.3 fm$^{-1}$. Implications for neutron star matter are examined, and suggest the existence of a $\Lambda$ $^1S_0$ superfluid between the threshold baryon density for $\Lambda$ formation and the baryon density where the $\Lambda$ fraction reaches $15-20$.Comment: 16 pages, Revtex, 9 figures, 33 reference

On the Surface Structure of Strange Superheavy Nuclei

Bound, strange, neutral superheavy nuclei, stable against strong decay, may exist. A model effective field theory calculation of the surface energy and density of such systems is carried out assuming vector meson couplings to conserved currents and scalar couplings fit to data where it exists. The non-linear relativistic mean field equations are solved assuming local baryon sources. The approach is calibrated through a successful calculation of the known nuclear surface tension.Comment: 12 pages, 9 figure

Phenomenological model for the Kbar N --> K Xi reaction

A phenomenological model for the Kbar N --> K Xi reaction is suggested. The model includes s and u channel exchanges by Lambda, Sigma, Sigma(1385), and Lambda(1520) and s channel exchanges by above-threshold hyperonic resonances. Explicit expression for the propagator for a particle with spin 7/2 is presented. High-mass and high-spin resonances play a significant role in the process. We deal with the whole set of existing experimental data on the cross sections and polarizations in the energy range from the threshold to 2.8 GeV in the center-of-mass system and reach a good agreement with experiments. Applications of the model to other elementary reactions of Xi production and to Xi hypernuclear spectroscopy are briefly discussed.Comment: Published version; minor change

Production of {\pi}+ and K+ mesons in argon-nucleus interactions at 3.2 AGeV

First physics results of the BM@N experiment at the Nuclotron/NICA complex are presented on {\pi}+ and K+ meson production in interactions of an argon beam with fixed targets of C, Al, Cu, Sn and Pb at 3.2 AGeV. Transverse momentum distributions, rapidity spectra and multiplicities of {\pi}+ and K+ mesons are measured. The results are compared with predictions of theoretical models and with other measurements at lower energies.Comment: 29 pages, 20 figure

Proton drip line for light hypernuclei

We determine the location of the proton drip line for light $$\Lambda$$ and $$\Lambda \Lambda$$ hypernuclei. While it is already known for $$1\le Z\le 4$$, our main focus is the $$5\le Z\le 8$$ range, and further conclusions are drawn for proton-rich $$\Lambda$$ hypernuclei up to $$Z = 20$$. $$\Lambda$$ binding energies from the Skyrme-Hartree-Fock calculation and the energies of unstable nuclei known experimentally are used. It is shown that $$^9_\Lambda$$C, $$^{10}_{\Lambda \Lambda }$$C and $$^{14}_{\Lambda \Lambda }$$O with unstable nuclear cores are bound whereas $$^8_\Lambda$$B, $$^{12}_\Lambda$$N, $$^{13}_\Lambda$$O and $$^{13}_{\Lambda \Lambda }$$N are not. Boundness of $$^9_{\Lambda \Lambda }$$B remains questionable. Among heavier systems, $$^{17}_\Lambda$$F, $$^{20}_\Lambda$$Na and $$^{20}_\Lambda$$Mg are shown to be the possible candidates for bound hypernuclei