arXiv subjects

J. Mareš

Publications and source records attributed to J. Mareš.

At least 19 recordsLinked to original sources

arXiv2025

Antikaon absorption in the nuclear medium: the role of hadron self-energies and implications for kaonic atoms

A systematic study of all relevant in-medium effects on the total $K^-$-nuclear potential is presented in this work. The $K^-N$ scattering amplitudes, including Pauli blocking effects and hadron self-energies (hyperons, nucleons, pions and kaons), are derived within a next-to-leading order chiral meson-baryon coupled-channel interaction model. These amplitudes are employed in a microscopic model of the $K^-$-nuclear potential in symmetric nuclear matter that includes one-, two- and, when the kaons and pions are dressed, also multinucleon absorption processes. The potential is then applied in calculations of the strong energy shifts and widths of 64 measured kaonic atom levels. The comparison of the results of the full model that includes Pauli correlations and hadron self-energies with data provides $χ^2 /d.p=1.5$, the lowest value obtained by a theoretical model to date and comparable with that of the best fitted phenomenological potentials. Furthermore, the calculated branching ratios for mesonic and non-mesonic absorption channels in kaonic carbon and kaonic neon are in good agreement with available data.

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arXiv2022

First application of a microscopic $K^-NN$ absorption model in calculations of kaonic atoms

Strong interaction energy shifts and widths in kaonic atoms are calculated for the first time using microscopic $K^- N$ + $K^- NN$ potentials derived from $K^- N$ scattering amplitudes constructed within SU(3) chiral coupled-channels models of meson-baryon interactions. The in-medium modifications of the free-space amplitudes due to the Pauli correlations are taken into account. The $K^-N+K^-NN$ potentials evaluated for 23 nuclear species are confronted with kaonic atoms data. The description of the data significantly improves when the $K^-NN$ absorption is included. To get $χ^2$ as low as for the $K^-N+$phenomenological multi-nucleon potential an additional phenomenological term, accounting for $K^{-}-3N(4N)$ processes, is still needed. However, density dependence of this phenomenological term points out some deficiencies in the microscopic potentials and further improvements of the applied model are thus desirable. The calculated branching ratios for $K^-N$ and $K^-NN$ absorption channels in the $^{12}$C$+K^-$ atom are in reasonable agreement with the old bubble chamber data, as well as with the latest data from the AMADEUS Collaboration.

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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 $B_Λ({_Λ^5}{\rm He})$.

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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.

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arXiv2020

$Λ^*$ matter and its stability

We performed calculations of nuclear systems composed solely of $Λ^*$ hyperons, aiming at exploring the possibility of existence of absolutely stable $Λ^*$ matter. We considered $Λ^*$ interaction strengths compatible with the $Λ^*Λ^*$ binding energy $B_{Λ^*Λ^*}$ given by the $\bar{K}N$ interaction model by Yamazaki and Akaishi [1]. We found that the binding energy per $Λ^*$ saturates at values well below 100 MeV for mass number $A\geq120$. The $Λ^*$ matter is thus highly unstable against strong interaction decay.

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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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arXiv2019

The onset of $ΛΛ$ hypernuclear binding

Binding energies of light, $A\leq 6$, $ΛΛ$ hypernuclei are calculated using the stochastic variational method in a pionless effective field theory (EFT) approach at leading order with the purpose of assessing critically the onset of binding in the strangeness S=-2 hadronic sector. The EFT input in this sector consists of (i) a $ΛΛ$ contact term constrained by the $ΛΛ$ scattering length $a_{ΛΛ}$, using a range of values compatible with $ΛΛ$ correlations observed in relativistic heavy ion collisions, and (ii) a $ΛΛN$ contact term constrained by the only available $A\leq 6$ $ΛΛ$ hypernucler binding energy datum of $^{6}_{ΛΛ}$He. The recently debated neutral three-body and four-body systems $^{3}_{ΛΛ}$n and $^{4}_{ΛΛ}$n are found unbound by a wide margin. A relatively large value of $|a_{ΛΛ}| \gtrsim 1.5$ fm is needed to bind $^{4}_{ΛΛ}$H, thereby questioning its particle stability. In contrast, the particle stability of the $A=5$ $ΛΛ$ hypernuclear isodoublet $^{5}_{ΛΛ} $H--$^{5}_{ΛΛ}$He is robust, with $Λ$ separation energy of order 1 MeV.

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arXiv2019

On the Stability of $Λ(1405)$ Matter

A hypothesis of absolutely stable strange hadronic matter composed of $Λ(1405)$ baryons, here denoted $Λ^*$, is tested within many-body calculations performed using the Relativistic Mean-Field approach. In our calculations, we employed the $Λ^*Λ^*$ interaction compatible with the $Λ^*Λ^*$ binding energy $B_{Λ^*Λ^*}=40$~MeV given by the phenomenological energy-independent $\bar{K}N$ interaction model by Yamazaki and Akaishi (YA). We found that the binding energy per $Λ^*$, as well as the central density in $Λ^*$ many-body systems saturates for mass number $A\geq120$, leaving $Λ^*$ aggregates highly unstable against strong interaction decay. Moreover, we confronted the YA interaction model with kaonic atom data and found that it fails to reproduce the $K^-$ single-nucleon absorption fractions at rest from bubble chamber experiments.

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arXiv2017

$K^-$- nuclear states: Binding energies and widths

$K^-$ optical potentials relevant to calculations of $K^-$ nuclear quasi-bound states were developed within several chiral meson-baryon coupled-channel interaction models. The applied models yield quite different $K^-$ binding energies and widths. Then, the $K^-$ multinucleon interactions were incorporated by a phenomenological optical potential fitted recently to kaonic atom data. Though the applied $K^-$ interaction models differ significantly in the $K^-N$ subthreshold region, our self-consistent calculations of kaonic nuclei across the periodic table lead to conclusions valid quite generally. Due to $K^-$ multinucleon absorption in the nuclear medium the calculated widths of $K^-$ nuclear states are sizable, $Γ_{K^-} \geq 90$ MeV, and exceed substantially their binding energies in all considered nuclei.

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arXiv2016

Calculations of kaonic nuclei based on chiral meson-baryon coupled channel interaction models

We present our latest calculations of $K^-$-nuclear quasi-bound states using a self-consistent scheme for constructing $K^-$-nuclear potentials from various subthreshold chirally inspired $\bar{K}N$ scattering amplitudes. We consider in-medium versions of the scattering amplitudes taking into account Pauli blocking in the intermediate states. The resulting $K^-$ binding energies as well as the widths exhibit the same A dependence, however, the binding energies strongly depend on the model used.

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arXiv2016

Sensitivity of Λ single-particle energies to the ΛN spin-orbit coupling and to nuclear core structure in p-shell and sd-shell hypernuclei

We introduce a mean field model based on realistic 2-body baryon interactions and calculate spectra of a set of p-shell and sd-shell Λ hypernuclei - 13ΛC, 17ΛO, 21ΛNe, 29ΛSi and 41ΛCa. The hypernuclear spectra are compared with the results of a relativistic mean field (RMF) model and available experimental data. The sensitivity of Λ single-particle energies to the nuclear core structure is explored. Special attention is paid to the effect of spin-orbit ΛN interaction on the energy splitting of the Λ single particle levels 0p3/2 and 0p1/2. In particular, we analyze the contribution of the symmetric (SLS) and the anti-symmetric (ALS) spin-orbit terms to the energy splitting. We give qualitative predictions for the calculated hypernuclei.

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arXiv2015

Interaction of antiprotons with nuclei

We performed fully self-consistent calculations of $\bar{p}$-nuclear bound states using a complex ${\bar p}$-nucleus potential accounting for $\bar{p}$-atom data. While the real part of the potential is constructed within the relativistic mean-field (RMF) model, the $\bar{p}$ annihilation in the nuclear medium is described by a phenomenological optical potential. We confirm large polarization effects of the nuclear core caused by the presence of the antiproton. The ${\bar p}$ annihilation is treated dynamically, taking into account explicitly the reduced phase space for annihilation from deeply bound states as well as the compressed nuclear density due to the antiproton. The energy available for the products of ${\bar p}$ annihilation in the nuclear medium is evaluated self-consistently, considering the additional energy shift due to transformation from the ${\bar p}N$ system to ${\bar p}$-nucleus system. Corresponding $\bar{p}$ widths in the medium are significantly suppressed, however, they still remain considerable for the $\bar{p}$ potential consistent with experimental data.

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arXiv2015

Interaction of antiproton with nuclei

We performed fully self-consistent calculations of $\bar{p}$-nuclear bound states within the relativistic mean-field (RMF) model. The G-parity motivated $\bar{p}$-meson coupling constants were adjusted to yield potentials consistent with $\bar{p}$-atom data. We confirmed large polarization effects of the nuclear core caused by the presence of the antiproton. The $\bar{p}$ absorption in the nucleus was incorporated by means of the imaginary part of a phenomenological optical potential. The phase space reduction for the $\bar{p}$ annihilation products was taken into account. The corresponding $\bar{p}$ width in the medium significantly decreases, however, it still remains considerable for the $\bar{p}$ potential consistent with experimental data.

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arXiv2014

Antibaryon-nucleus bound states

We calculated antibaryon ($\bar{B}$ = $\bar{p}$, $\barΛ$, $\barΣ$, $\barΞ$) bound states in selected nuclei within the relativistic mean-field (RMF) model. The G-parity motivated $\bar{B}$-meson coupling constants were scaled to yield corresponding potentials consistent with available experimental data. Large polarization of the nuclear core caused by $\bar{B}$ was confirmed. The $\bar{p}$ annihilation in the nuclear medium was incorporated by including a phenomenological imaginary part of the optical potential. The calculations using a complex $\bar{p}$-nucleus potential were performed fully self-consistently. The $\bar{p}$ widths significantly decrease when the phase space reduction is considered for $\bar{p}$ annihilation products, but they still remain sizeable for potentials consistent with $\bar{p}$-atom data.

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arXiv2014

In-medium Eta-Nucleon interactions and Eta nuclear bound states

The in-medium Eta-N interaction near and below threshold is constructed from a free-space chirally-inspired meson-baryon coupled-channel model that captures the physics of the N(1535) baryon resonance. Nucleon Pauli blocking and hadron self-energies are accounted for. The resulting energy dependent in-medium interaction is used in self-consistent dynamical calculations of Eta nuclear bound states. Narrow states of width about or less than 2 MeV are found across the periodic table, beginning with A=10, for this in-medium coupled-channel interaction model. The binding energy of the 1s-Eta state increases with A, reaching a value of B(1s-Eta) about 15 MeV. The implications of our self-consistency procedure are discussed with respect to procedures used in other works.

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arXiv2013

No-Core Shell Model for Nuclear Systems with Strangeness

We report on a novel ab initio approach for nuclear few- and many-body systems with strangeness. Recently, we developed a relevant no-core shell model technique which we successfully applied in first calculations of lightest $Λ$ hypernuclei. The use of a translationally invariant finite harmonic oscillator basis allows us to employ large model spaces, compared to traditional shell model calculations, and use realistic nucleon-nucleon and nucleon-hyperon interactions (such as those derived from EFT). We discuss formal aspects of the methodology, show first demonstrative results for ${}_Λ^3$H, ${}_Λ^4$H and ${}^4_Λ$He, and give outlook.

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arXiv2013

Eta-nuclear bound states revisited

The strong energy dependence of the s-wave eta-N scattering amplitude at and below threshold, as evident in coupled-channels K-matrix fits and chiral models that incorporate the S11 N*(1535) resonance, is included self-consistently in eta-nuclear bound-state calculations. This approach, applied recently in calculations of kaonic atoms and Kbar-nuclear bound states, is found to impose stronger constraints than ever on the onset of eta-nuclear binding, with a minimum value of Re a_{eta N} approximately 0.9 fm required to accommodate an eta-4He bound state. Binding energies and widths of eta-nuclear states are calculated within several underlying eta-N models for nuclei across the periodic table, including eta-25Mg for which some evidence was proposed in a recent COSY experiment.

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arXiv2011

K^- nuclear potentials from in-medium chirally motivated models

A self consistent scheme for constructing K^- nuclear optical potentials from subthreshold in-medium Kbar-N s-wave scattering amplitudes is presented and applied to analysis of kaonic atoms data and to calculations of K^- quasibound nuclear states. The amplitudes are taken from a chirally motivated meson-baryon coupled-channel model, both at the Tomozawa-Weinberg leading order and at the next to leading order. Typical kaonic atoms potentials are characterized by a real part -Re V(K^-;chiral)=(85+/-5) MeV at nuclear matter density, in contrast to half this depth obtained in some derivations based on in-medium Kbar-N threshold amplitudes. The moderate agreement with data is much improved by adding complex rho- and rho^2-dependent phenomenological terms, found to be dominated by rho^2 contributions that could represent Kbar-NN -> YN absorption and dispersion, outside the scope of meson-baryon chiral models. Depths of the real potentials are then near 180 MeV. The effects of p-wave interactions are studied and found secondary to those of the dominant s-wave contributions. The in-medium dynamics of the coupled-channel model is discussed and systematic studies of K^- quasibound nuclear states are presented.

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