arXiv subjects

Eliahu Friedman

Publications and source records attributed to Eliahu Friedman.

10 recordsLinked to original sources

arXiv2026

Hypernuclear constraints on $\Lambda N$ and $\Lambda NN$ interactions

Recent work on using density dependent $\Lambda$-nuclear optical potentials in calculations of $\Lambda$-hypernuclear binding energies is reviewed. It is found that all known $\Lambda$ binding energies in the mass range $16 \leq A \leq 208$ are well fitted in terms of two interaction parameters: one, attractive, for the spin-averaged $\Lambda N$ interaction and another one, repulsive, for the $\Lambda NN$ interaction. The $\Lambda N$ interaction term by itself overbinds $\Lambda$ hypernuclei, in quantitative agreement with recent findings obtained in EFT and Femtoscopy studies. The strength of the $\Lambda NN$ interaction term is compatible with values required to resolve the hyperon puzzle.

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arXiv2024

$\Lambda NN$ input to neutron stars from hypernuclear data

This work is a sequel to our two 2023 publications [PLB 837 137669, NPA 1039 122725] where fitting 14 1$s_\Lambda$ and 1$p_\Lambda$ single-particle binding energies in hypernuclei across the periodic table led to a well-defined $\Lambda$-nucleus optical potential. The potential consists of a Pauli modified linear-density ($\Lambda N$) and a quadratic-density ($\Lambda NN$) terms. The present work reports on extending the above analysis to 21 $\Lambda$ single-particle data points input by including 1$d_\Lambda$ and 1$f_\Lambda$ states in medium-weight and heavy hypernuclei. The upgraded results for the $\Lambda N$ and $\Lambda NN$ potential depths at nuclear-matter density $\rho_0=0.17$~fm$^{-3}$, $D^{(2)}_\Lambda=-37.5\mp 0.7$~MeV and $D^{(3)}_\Lambda=+9.8\pm 1.2$~MeV together with the total depth $D_\Lambda=-27.7\pm 0.5$~MeV, agree within errors with the earlier results. The $\Lambda$ hypernuclear overbinding associated with the $\Lambda N$-induced potential depth $D^{(2)}_\Lambda$ agrees quantitatively with a recent combined analysis of low-energy $\Lambda p$ scattering data and correlation functions [PLB 850 (2024) 138550]. These results, particularly the size of the repulsive $D^{(3)}_\Lambda$, provide an essential input towards resolving the 'hyperon puzzle' in the core of neutron stars. We also show that a key property of our $\Lambda NN$-induced potential term, i.e. a need to suppress the quadratic-density $\Lambda NN$ term involving an excess neutron and a $N=Z$ core nucleon, can be tested in the forthcoming JLab E12-15-008 experiment.

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arXiv2024

Deciphering $Ξ^-$ capture events in light emulsion nuclei

We recently showed that all five KEK and J-PARC uniquely assigned two-body $Ξ^-$+${^A}$Z$\to{_Λ^{A'}}$Z'+${_Λ^{A''}}$Z'' capture events in CNO light emulsion nuclei are consistent with Coulomb-assisted $1p_{Ξ^-}$ nuclear states in a $Ξ$-nuclear potential of nuclear-matter depth $V_Ξ\gtrsim 20$ MeV [1]. Here we argue that the recently reported $^{14}$N capture events named KINKA and IRRAWADDY are more likely $1p_{Ξ^0}$--$^{14}$C nuclear states [2] than $1s_{Ξ^-}$--$^{14}$N states, the latter assignment implying considerably smaller values of $V_Ξ$.

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arXiv2023

$ΛNN$ content of $Λ$-nucleus potential

A minimally constructed $Λ$-nucleus density-dependent optical potential is used to calculate binding energies of observed $1s_Λ$, $1p_Λ$ states across the periodic table, leading to a repulsive $ΛNN$ contribution $D_Λ^{(3)}\approx 14$ MeV to the phenomenological $Λ$-nucleus potential depth $D_Λ\approx -30$ MeV. This value is significant in connection with the so-called 'hyperon puzzle'.

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arXiv2022

$Ξ$-nuclear constraints from $Ξ^-$ emulsion capture events

All five KEK and J-PARC two-body $Ξ^-$+$^A$Z $\to$ $^{A'}_Λ$Z'+$^{A''}_Λ$Z'' capture events in light emulsion nuclei, including KISO and IBUKI in $^{14}$N, are consistent with Coulomb-assisted $1p_{Ξ^-}$ nuclear states. The underlying $Ξ$-nuclear potential is strongly attractive, with nuclear-matter depth $V_Ξ$ larger than 20 MeV. The recent $^{14}$N capture events KINKA and IRRAWADDY assigned by J-PARC E07 to $1s_{Ξ^-}$ nuclear states, and implying considerably shallower $V_Ξ$, have also another interpretation as $1p_{Ξ^0}$ nuclear states.

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arXiv2020

Extracting $σ_{πN}$ from pionic atoms

We discuss a recent extraction of the $πN$ $σ$ term $σ_{πN}$ from a large-scale fit of pionic-atom strong-interaction data across the periodic table. The value thus derived, $σ_{πN}^{\rm FG}=57\pm 7$ MeV, is directly connected via the Gell-Mann--Oakes--Renner expression to the medium-renormalized $πN$ isovector scattering amplitude near threshold. It compares well with the value derived recently by the Bern-Bonn-Jülich group, $σ_{πN}^{\rm RS}=58\pm 5$ MeV, using the Roy-Steiner equations to control the extrapolation of the vanishingly small near threshold $πN$ isoscalar scattering amplitude to zero pion mass.

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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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arXiv2018

$Λ^{\ast}(1405)$-matter: stable or unstable?

A recent suggestion [PLB 774 (2017) 522] that purely-$Λ^{\ast}(1405)$ nuclei provide the absolute minimum energy in charge-neutral baryon matter for baryon-number $A\gtrsim 8$, is tested within RMF calculations. A broad range of $Λ^{\ast}$ interaction strengths, commensurate with $(\bar K \bar K NN)_{I=0}$ binding energy assumed to be of order 100 MeV, is scanned. It is found that the binding energy per $Λ^{\ast}$, $B/A$, saturates for $A\gtrsim 120$ with values of $B/A$ considerably below 100 MeV, implying that $Λ^{\ast}(1405)$ matter is highly unstable against strong decay to $Λ$ and $Σ$ hyperon aggregates. The central density of $Λ^{\ast}$ matter is found to saturate as well, at roughly twice nuclear matter density. Moreover, it is shown that the underlying very strong $\bar K N$ potentials, fitted for isospin $I=0$ to the mass and width values of $Λ^{\ast}(1405)$, fail to reproduce values of single-nucleon absorption fractions deduced across the periodic table from $K^-$ capture-at-rest bubble chamber experiments.

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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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