arXiv subjects

Aleš Cieplý

Publications and source records attributed to Aleš Cieplý.

7 recordsLinked to original sources

arXiv2021

Model selection for $K^+Σ^-$ photoproduction within isobar model

We utilise an isobar model to investigate the $K^+ Σ^-$ photoproduction off a neutron in the resonance region. Except for the Born terms, we include high-spin (spin-3/2 and spin-5/2) nucleon resonances in the consistent formalism together with a few $Δ$ and kaon resonances to achieve an acceptable agreement with data. Interestingly, we reveal that no hyperon resonances are needed to achieve a reasonable description of data. On the other hand the $N(1720)3/2^+$ resonance was found to be very important for correct description of data. The free parameters of the model were fitted to experimental data from the LEPS and CLAS Collaborations on either differential cross sections or photon beam asymmetry. The novel feature of the fitting procedure is the use of a regularization method, the Least Absolute Shrinkage Selection Operator, and information criteria in order to choose the best fit.

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arXiv2020

From $\bar{K}N$ Interactions to $\bar{K}$-Nuclear Quasi-Bound States

We review the current status of our study of $K^-$-nuclear interactions and $K^-$-nuclear quasi-bound states. The adopted $K^-$-nuclear optical potential consists of two parts -- the single-nucleon one constructed microscopically from chirally motivated $\bar{K}N$ amplitudes, and a phenomenological multi-nucleon one constrained in fits to kaonic atoms data. The inclusion of multi-nucleon absorption in our calculations of $K^{-}$ quasi-bound states in many-body systems leads to huge widths, considerably exceeding the binding energies. If this feature is confirmed the observation of such states is unlikely. Finally, a development of a new microscopical model for in-medium $K^-NN$ absorption is discussed as well.

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arXiv2017

Onset of $η$ nuclear binding

Recent studies of $η$ nuclear quasibound states by the Jerusalem-Prague Collaboration are reviewed, focusing on stochastic variational method self consistent calculations of $η$ few-nucleon systems. These calculations suggest that a minimum value Re$\,a_{ηN} \approx 1$ fm (0.7 fm) is needed to bind $η\,^3$He ($η\,^4$He).

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arXiv2017

Studies of mesic atoms and nuclei

$K^-$ mesons offer a unique setting where mesic atoms have been studied both experimentally and theoretically, thereby placing constraints on the possible existence and properties of meson-nuclear quasibound states. Here we review progress in this field made recently by the Jerusalem--Prague Collaboration using near-threshold $K^-N$ scattering amplitudes generated in several meson--baryon coupled channels models inspired by a chiral EFT approach. Our own procedure of handling subthreshold kinematics self consistently is used to transform these free-space energy dependent amplitudes to in-medium density dependent amplitudes from which $K^-$ optical potentials are derived. To fit the world data of kaonic atoms, these single-nucleon optical potentials are augmented by multi-nucleon terms. It is found that only two of the studied models reproduce also the single-nucleon absorption fractions available from old bubble chamber experiments. These two models are then checked for possible $K^-$ nuclear quasibound states, despite realizing that $K^-$ optical potentials are not constrained by kaonic atom data at densities exceeding half nuclear-matter density. We find that when such states exist, their widths are invariably above 100 MeV, forbiddingly large to allow observation. Multi-nucleon absorption is found to be substantial in this respect. This suggests that observable strongly bound $K^-$ mesons are limited to the very light systems, such as $K^-pp$.

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arXiv2015

Effective model for in-medium $\bar{K}N$ interactions including the $L=1$ partial wave

Coupled channels model of meson-baryon interactions based on the effective chiral Lagrangian is extended to account explicitly for the $Σ(1385)$ resonance that dominates the $P$-wave $\bar{K}N$ and $πΣ$ interactions at energies below the $\bar{K}N$ threshold. The presented model aims at a uniform treatment of the $Λ(1405)$ and $Σ(1385)$ dynamics in the nuclear medium. We demonstrate the applicability of the model by confronting its predictions with the vacuum scattering data, then we follow with discussing the impact of nuclear matter on the $πΣ$ mass spectrum and on the energy dependence of the $K^{-}p$ branching ratios.

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arXiv2014

In-medium antikaon interactions and bound states

Correct treatment of subthreshold Kbar-N dynamics is mandatory in kaonic-atom and Kbar-nuclear bound-state calculations, as demonstrated by using in-medium chirally-based models of Kbar-N interactions. Recent studies of kaonic-atom data reveal appreciable multi-nucleon contributions. Kbar-nuclear widths larger than 50 MeV are anticipated.

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arXiv2014

In-medium antikaon and eta-meson interactions and bound states

The role played by subthreshold meson-baryon dynamics is demonstrated in kaonic-atom, Kbar-nuclear and eta-nuclear bound-state calculations within in-medium models of Kbar-N and eta-N interactions. New analyses of kaonic atom data reveal appreciable multi-nucleon contributions. Calculations of eta-nuclear bound states show, in particular, that the eta-N scattering length is not a useful indicator of whether or not eta mesons bind in nuclei nor of the widths anticipated for such states.

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