arXiv subjects

B. Bazak

Publications and source records attributed to B. Bazak.

6 recordsLinked to original sources

arXiv2022

Consequences of increased hypertriton binding for $s$-shell $Λ$-hypernuclear systems

Consequences of increasing the binding energy of the hypertriton ground state ${_Λ^3}{\rm H}(J^P={\frac{1}{2}}^+)$ from the emulsion value $B^{\rm EMUL}_Λ({_Λ^3}{\rm H}_{\rm g.s.})$=0.13$\pm$0.05 MeV to the STAR value $B^{\rm STAR}_Λ(^{3}_Λ{\rm H}) = (0.41\pm 0.12 \pm 0.11)$ MeV are studied for $s$-shell hypernuclei within a pionless EFT approach at leading order, constrained by the binding energies of the $0^+$ and $1^+$ ${_Λ^4} {\rm H}$ states. The stochastic variational method is used in bound-state calculations, whereas the inverse analytic continuation in the coupling constant method is used to locate $S$-matrix poles of continuum states. It is found that the $Λnn({\frac{1}{2}}^+)$ resonance becomes broader and less likely to be observed experimentally, whereas the ${_Λ^3}{\rm H}({\frac{3}{2}}^+)$ spin-flip virtual state moves closer to the $Λd$ threshold to become a shallow bound state for specific $ΛN$ interaction strengths. The effect of such a near-threshold ${_Λ^3}{\rm H}({\frac{3}{2}}^+)$ state on femtoscopic studies of $Λ$-deuteron correlations, and its lifetime if bound, are discussed. Increasing $B_Λ({_Λ^3} {\rm H}_{\rm g.s.})$ moderately, up to $\sim$0.5 MeV, hardly affects calculated values of $B_Λ({_Λ^5}{\rm He})$.

nucl-th↗

arXiv2021

Nature of the $Λnn$ $(J^π=1/2^+, I=1)$ and ${\rm ^3_ΛH^*} (J^π=3/2^+, I=0)$ states

The nature of the $Λnn$ and ${\rm ^3_ΛH^*} (J^π=3/2^+,~I=0)$ states is investigated within a pionless effective field theory at leading order, constrained by the low energy $ΛN$ scattering data and hypernuclear 3- and 4-body data. Bound state solutions are obtained using the stochastic variational method, the continuum region is studied by employing two independent methods - the inverse analytic continuation in the coupling constant method and the complex scaling method. Our calculations yield both the $Λnn$ and ${\rm ^3_ΛH^*}$ states unbound. We conclude that the excited state ${\rm ^3_ΛH^*}$ is a virtual state and the $Λnn$ pole located close to the three-body threshold in a complex energy plane could convert to a true resonance with Re$(E)>0$ for some considered $ΛN$ interactions. Finally, the stability of resonance solutions is discussed and limits of the accuracy of performed calculations are assessed.

nucl-th↗

arXiv2020

Few-body bound states of two-dimensional bosons

We study clusters of the type A$_N$B$_M$ with $N\leq M\leq 3$ in a two-dimensional mixture of A and B bosons, with attractive AB and equally repulsive AA and BB interactions. In order to check universal aspects of the problem, we choose two very different models: dipolar bosons in a bilayer geometry and particles interacting via separable Gaussian potentials. We find that all the considered clusters are bound and that their energies are universal functions of the scattering lengths $a_{AB}$ and $a_{AA}=a_{BB}$, for sufficiently large attraction-to-repulsion ratios $a_{AB}/a_{BB}$. When $a_{AB}/a_{BB}$ decreases below $\approx 10$, the dimer-dimer interaction changes from attractive to repulsive and the population-balanced AABB and AAABBB clusters break into AB dimers. Calculating the AAABBB hexamer energy just below this threshold, we find an effective three-dimer repulsion which may have important implications for the many-body problem, particularly for observing liquid and supersolid states of dipolar dimers in the bilayer geometry. The population-imbalanced ABB trimer, ABBB tetramer, and AABBB pentamer remain bound beyond the dimer-dimer threshold. In the dipolar model, they break up at $a_{AB}\approx 2 a_{BB}$ where the atom-dimer interaction switches to repulsion.

cond-mat.quant-gas↗

arXiv2020

The Continuum Spectrum of Hypernuclear Trios

The spectrum of hypernuclear trios composed of a $Λ$ baryon and two nucleons is the subject of an ongoing experimental campaign, aiming to study the interaction of the $Λ$ particle with a neutron, and the 3-body $Λ$-nucleon-nucleon force. In this manuscript we utilize baryonic effective field theory at leading order, constrained to reproduce the available low energy light hypernuclear data, to study the continuum spectrum of such hypernuclear trios. Using the complex scaling method and the inverse analytic continuation in the coupling constant method we find the existence of a virtual state in the $Λn p$ $J^π=\frac{3}{2}^{+}$ channel, leading to cross-section enhancement near threshold. For the $Λn n$ $J^π=\frac{1}{2}^{+}$ channel we predict a resonance state. Depending, however, on the value of the $ΛN$ scattering length, the resonance pole moves from the physical to the unphysical complex energy sheet within the experimental bounds.

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arXiv2017

Eta-mesic nuclei

In this contribution we report on theoretical studies of $η$ nuclear quasi-bound states in few- and many-body systems performed recently by the Jerusalem-Prague Collaboration [1-5]. Underlying energy-dependent $ηN$ interactions are derived from coupled-channel models that incorporate the $N^*(1535)$ resonance. The role of self-consistent treatment of the strong energy dependence of subthreshold $ηN$ amplitudes is discussed. Quite large downward energy shift together with rapid decrease of the $ηN$ amplitudes below threshold result in relatively small binding energies and widths of the calculated $η$ nuclear bound states. We argue that the subthreshold behavior of $ηN$ scattering amplitudes is crucial to conclude whether $η$ nuclear states exist, in which nuclei the $η$ meson could be bound and if the corresponding widths are small enough to allow detection of these $η$ nuclear states in experiment.

nucl-th↗

arXiv2017

Onset of $η$-nuclear binding in a pionless EFT approach

$ηNNN$ and $ηNNNN$ bound states are explored in stochastic variational method (SVM) calculations within a pionless effective field theory (EFT) approach at leading order. The theoretical input consists of regulated $NN$ and $NNN$ contact terms, and a regulated energy dependent $ηN$ contact term derived from coupled-channel models of the $N^{\ast}(1535)$ nucleon resonance plus a regulated $ηNN$ contact term. A self consistency procedure is applied to deal with the energy dependence of the $ηN$ subthreshold input, resulting in a weak dependence of the calculated $η$-nuclear binding energies on the EFT regulator. It is found, in terms of the $ηN$ scattering length $a_{ηN}$, that the onset of binding $η\,^3$He requires a minimal value of Re$\,a_{ηN}$ close to 1 fm, yielding then a few MeV $η$ binding in $η\,^4$He. The onset of binding $η\,^4$He requires a lower value of Re$\,a_{ηN}$, but exceeding 0.7 fm.

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