arXiv subjects

Johann Haidenbauer

Publications and source records attributed to Johann Haidenbauer.

At least 19 recordsLinked to original sources

arXiv2026

Hyperon single-particle potentials in nuclear matter based on baryon-baryon interactions derived within chiral effective field theory

An analysis of the Lambda and Sigma single-particle potentials is presented, based on YN interactions derived within chiral effective field theory up to next-to-next-to-leading order (N$^2$LO). The self-consistent Brueckner-Hartree-Fock framework is employed within the continuous choice for the single-particle potential. The result for the Lambda single-particle potential is comparable to the ones obtained with previous chiral YN interactions up to next-to-leading order (NLO). The Sigma single-particle potential is found weakly attractive, in contrast to earlier weakly repulsive results, reflecting new constraints from the recent J-PARC E40 data on $Σ^+p$ scattering. An estimate of the theoretical uncertainty of the single-particle potentials is provided.

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arXiv2025

Properties of hyperons in nuclear matter from chiral hyperon-nucleon interactions at next-to-next-to-leading order

The $Λ$ and $Σ$ single-particle potentials in infinite nuclear matter are analyzed within a recently established chiral hyperon-nucleon ($YN$) interaction up to N$^2$LO in combination with an nucleon-nucleon interaction derived in the same scheme. The self-consistent Brueckner-Hartree-Fock method with the continuous choice of the single-particle potential is employed. It is found that the $Λ$ single-particle potential is comparable to the results achieved with the NLO $YN$ interaction from 2019. The resulting $Σ$ potential becomes more attractive compared to the previous NLO results due to the constraint from the recent $ΣN$ differential cross section data measured in the J-PARC E40 experiment. An estimate of the theoretical uncertainty of the single-particle potentials is provided in terms of the truncation error in the chiral expansion.

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arXiv2025

Dynamical coupled-channel models for hadron dynamics

Dynamical coupled-channel (DCC) approaches parametrize the interactions and dynamics of two and more hadrons and their response to different electroweak probes. The inclusion of unitarity, three-body channels, and other properties from scattering theory allows for a reliable extraction of resonance spectra and their properties from data. We review the formalism and application of the ANL-Osaka, the Juelich-Bonn-Washington, and other DCC approaches in the context of light baryon resonances from meson, (virtual) photon, and neutrino-induced reactions, as well as production reactions, strange baryons, light mesons, heavy meson systems, exotics, and baryon-baryon interactions. Finally, we also provide a connection of the formalism to study finite-volume spectra obtained in Lattice QCD, and review applications involving modern statistical and machine learning tools.

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arXiv2025

$Λ$ and $Σ$ potentials in dense matter based on chiral EFT: Bridging heavy-ion collisions, hypernuclei, and neutron stars

The $Λ$ and $Σ$ directed flows at $\sqrt{s_{NN}}=4.5~\mathrm{GeV}$ are investigated to examine their sensitivity to the hyperon single-particle potentials. The single-particle potentials are obtained from $G$-matrix calculations with two- and three-body forces based on SU(3) chiral effective field theory. The $Λ+Σ^0$ directed flow shows sensitivity to the variation in the $Σ$ single-particle potential. Its effect is more pronounced for the $Σ^0$ directed flow.

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arXiv2025

Ab initio description of hypernuclei

Hypernuclei are bound states of neutrons, protons and one or two hyperons, thus extending the nuclear landscape to a third dimension. They also encode information about the baryon-baryon and three-baryon interactions. Here, we review recent work on chiral effective field theory for two- and three-baryon interactions and their application in nuclei based on ab initio methods. These include the Faddeev-Yakubovsky equations, the no-core-shell-model (NCSM) and nuclear lattice effective field theory (NLEFT). Besides of providing an overview of the formalisms explicit results for the separation energies of light $Λ$ hypernuclei are provided. Two-body and three-body forces are included consistently, in line with the underlying power counting. Calculations of $Λ$ hypernuclei within the NCSM, performed up to A=7 so far, suggest that agreement with the experimental binding energies can be achieved once appropriate three-body forces are taken into account. Similar conclusions are drawn from the study based on NLEFT, where even hypernuclei up to A=16 can be computed. Additionally, applications of ab initio approaches in calculations of $ΛΛ$ and $Ξ$ hypernuclei are discussed and possible candidates for the lightest systems that could be bound are identified, namely $^{\ \ 5}_{ΛΛ}{\rm He}$ and $^4_Ξ{\rm H}$.

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arXiv2024

Electromagnetic form factors of hyperons in the timelike region: A short review

We review recent experimental and theoretical results for the electromagnetic form factors of hyperons (Y) in the timelike region, accessible in the reactions $e^+e^-\to \bar YY$. Specifically, we focus on the final states $\bar ΛΛ$, $\barΛΣ^0$/$\bar Σ^0Λ$, $\bar ΣΣ$, $\bar ΞΞ$, and $\barΩΩ$. The $\bar Λ_cΛ_c$ system is also discussed.

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arXiv2024

Light $Λ$ hypernuclei studied with chiral hyperon-nucleon and hyperon-nucleon-nucleon forces

A study of light $Λ$ hypernuclei in chiral effective field theory is presented. For the first time chiral $Λ$NN and $Σ$NN three-body forces are included consistently. The calculations are performed within the no-core shell model. Results for the separation energies of the hypernuclei $^3_Λ\mathrm{H}$, $^4_Λ\mathrm{H}$/$^4_Λ\mathrm{He}$, $^5_Λ\mathrm{He}$, and $^7_Λ\mathrm{Li}$ are given. It is found that the experimental values can be fairly well reproduced once YNN three-body forces are taken into account.

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arXiv2024

Benchmarking $Λ$NN three-body forces and first predictions for A=3-5 hypernuclei

Explicit expressions for the leading chiral hyperon-nucleon-nucleon three-body forces have been derived by Petschauer et al [Phys. Rev. C93.014001 (2016)]. An important prerequisite for including these three-body forces in few- and many-body calculations is the accuracy and efficiency of their partial-wave decomposition. A careful benchmark of the ΛNN potential matrix elements, computed using two robust and efficient partial-wave decomposition methods, is presented. In addition, results of a first quantitative assessment for the contributions of $Λ$NN forces to the separation energies in A=3-5 hypernuclei are reported.

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arXiv2024

Study of the electromagnetic form factors of the nucleons in the timelike region

The electromagnetic form factors $G_{\rm E}$ and $G_{\rm M}$ of the proton and neutron in the timelike region are extracted in a study of the processes $e^+ e^-\to \bar{p}p$ and $e^+ e^-\to \bar{n}n$. The reaction amplitude is evaluated within the distorted wave Born approximation, with the interaction of the antinucleon-nucleon ($\bar{N}N$) pair taken into account. The latter is constructed within $SU(3)$ chiral effective field theory up to the next-to-leading order. An excellent description of the $e^+ e^-\to \bar{N}N$ data in the energy region from the $\bar{N}N$ threshold up to center-of-mass energies $E_{\rm cm}=2.2$~GeV is achieved. Results for the electromagnetic form factors $G_{\rm E}, G_{\rm M}$, $G_{\rm E}/G_{\rm M}$, and the subtracted effective form factors, $G_{\rm osc}$, are provided. These can be helpful for further studies of the properties of the nucleons.

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arXiv2024

Separation energies of light $Λ$ hypernuclei and their theoretical uncertainties

Separation energies of light $Λ$ hypernuclei ($A\leq 5$) and their theoretical uncertainties are investigated. Few-body calculations are performed within the Faddeev-Yakubovsky scheme and the no-core shell model. Thereby, modern and up-to-date $N\!N$ and $Y\!N$ potentials derived within chiral effective field theory are employed. % It is found that the numerical uncertainties of the few-body methods are well under control and an accuracy of around $1$ keV for the hypertriton and of less than $20$ keV for the separation energies of the $^4_Λ\mathrm{He}$ and $^5_Λ\mathrm{He}$ hypernuclei can be achieved. Variations caused by differences in the $N\!N$ interaction are in the order of $10$ keV for $^3_Λ\mathrm{H}$ and no more than $110$ keV for $A=4,\,5$ $Λ$ hypernuclei, when recent high-precision potentials up to fifth order in the chiral expansion are employed. The variations are smaller than expected contributions from chiral $Y\!N\!N$ three-body forces (3BFs) which arise at the chiral order of state-of-the-art $Y\!N$ potentials. Estimates for those 3BFs are deduced from a study of the truncation uncertainties in the chiral expansion.

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arXiv2023

New insights into the oscillation of the nucleon electromagnetic form factors

The electromagnetic form factors of the proton and the neutron in the timelike region are investigated. Electron-positron annihilation into antinucleon-nucleon ($\bar NN$) pairs is treated in distorted wave Born approximation, including the final-state interaction in the $\bar NN$ system. The latter is obtained by a Lippmann-Schwinger equation for $\bar{N}N$ potentials derived within SU(3) chiral effective field theory. By fitting to the phase shifts and (differential) cross section data, a high quality description is achieved. With these amplitudes, the oscillations of the electromagnetic form factors of the proton and the neutron are studied. It is found that each of them can be described by two fractional oscillators. One is characterized as \lq overdamped' and dominates near the threshold, while the other is \lq underdamped' and plays an important role in the high-energy region. These two oscillators are essential to understand the distributions of polarized electric charges induced by hard photons for the nucleons.

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arXiv2023

$Λ\barΛ$ final-state interaction in the reactions $e^+e^-\to ϕΛ\bar Λ$ and $e^+e^- \to ηΛ\bar Λ$

Near-threshold $Λ\barΛ$ mass spectra for the reactions $e^+e^- \to ηΛ\barΛ$ and $e^+e^- \to ϕΛ\barΛ$ are investigated with an emphasis on the role played by the interaction in the $Λ\barΛ$ system. A variety of $Λ\barΛ$ potential models is employed that have been established in the analysis of data on $p\bar p\to Λ\barΛ$ in the past. It is shown that the near-threshold enhancement observed for the two $e^+e^-$ reactions can be reproduced by considering the $Λ\barΛ$ final-state interaction in the partial waves suggested by the helicity-angle analysis of the experiments. For $e^+e^- \to ηΛ\barΛ$ the same $Λ\barΛ$ $S$-wave interaction as in $e^+e^- \to Λ\barΛ$ is relevant and with it a consistent description of the pertinent measurements can be achieved. It is pointed out that a nonzero threshold cross section as observed for the latter reaction is not supported by the new $ηΛ\barΛ$ data.

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arXiv2023

Ab initio calculation of charge symmetry breaking in $A=7$ and $8$ $Λ$-hypernuclei

The separation energies of the isospin triplet $^7_Λ\mathrm{He}$, $^7_Λ\mathrm{Li^{*}}$, $^7_Λ$Be, and the $T=1/2$ doublet $^8_Λ$Li, $^8_Λ$Be are investigated within the no-core shell model. Calculations are performed based on a hyperon-nucleon potential derived from chiral effective field theory at next-to-leading order. The potential includes the leading charge-symmetry breaking (CSB) interaction in the $Λ$N channel, whose strength has been fixed to the experimentally known difference of the $Λ$ separation energies of the mirror hypernuclei $^4_Λ\mathrm{He}$ and $^4_Λ\mathrm{H}$. It turns out that the CSB predicted for the $A=7$ systems is small and agrees with the splittings deduced from the empirical binding energies within the experimental uncertainty. In case of the $A=8$ doublet, the computed CSB is somewhat larger than the available experimental value. Using other experimental input for $A=4$ can change this prediction moving it closer to experiment.

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arXiv2023

Hyperon-nucleon interaction in chiral effective field theory at next-to-next-to-leading order

A hyperon-nucleon potential for the strangeness $S=-1$ sector ($ΛN$, $ΣN$) up to third order in the chiral expansion is presented. SU(3) flavor symmetry is imposed for constructing the interaction, however, the explicit SU(3) symmetry breaking by the physical masses of the pseudoscalar mesons and in the leading-order contact terms is taken into account. A novel regularization scheme is employed which has already been successfully used in studies of the nucleon-nucleon interaction within chiral effective field theory up to high orders. An excellent description of the low-energy $Λp$, $Σ^- p$ and $Σ^+ p$ scattering data is achieved. New data from J-PARC on angular distributions for the $ΣN$ channels are analyzed. Results for the hypertriton and $A=4$ hyper-nuclear separation energies are presented. An uncertainty estimate for the chiral expansion is performed for selected hyperon-nucleon observables.

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arXiv2022

Constraints on the Lambda-neutron interaction from charge-symmetry breaking of A=4 hypernuclei

We include the leading charge symmetry breaking contributions into the hyperon-nucleon interactions derived within chiral effective field theory up to next-to-leading order. Two low energy constants are determined using the experimentally known differences of Lambda separation energies of 4-Lambda-He and 4-Lambda-H. This allows one to predict the Lambda-neutron scattering lengths for the first time based on data. Various sources of uncertainty are discussed.

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arXiv2021

$A=4-7$ $Ξ$ hypernuclei based on interactions from chiral effective field theory

We investigate the existence of bound $Ξ$ \break states in systems with $A=4-7$ baryons using the Jacobi NCSM approach in combination with chiral NN and $Ξ$N interactions. We find three shallow bound states for the NNN$Ξ$ system (with $(J^π,T)=(1^+,0)$, $(0^+,1)$ and $(1^+,1)$) with quite similar binding energies. The $^5_Ξ\mathrm{H}(\frac{1}{2}^+,\frac{1}{2})$ and $^7_Ξ\mathrm{H}(\frac{1}{2}^+,\frac{3}{2})$ hypernuclei are also clearly bound with respect to the thresholds $^4\mathrm{He} + Ξ$ and $^6\mathrm{He} +Ξ$, respectively. The binding of all these $Ξ$ systems is predominantly due to the attraction of the chiral $Ξ$N potential in the $^{33}S_1$ channel. A perturbative estimation suggests that the decay widths of all the observed states could be rather small.

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arXiv2021

Constraints on the $Λ$-neutron interaction from charge symmetry breaking in the $\mathbf{^4_Λ\rm \bf He}$--$\mathbf{^4_Λ\rm \bf H}$ hypernuclei

We utilize the experimentally known difference of the $Λ$ separation energies of the mirror hypernuclei ${^4_Λ\rm He}$ and ${^4_Λ\rm H}$ to constrain the $Λ$-neutron interaction. We include the leading charge-symmetry breaking (CSB) interaction into our hyperon-nucleon interaction derived within chiral effective field theory at next-to-leading order. In particular, we determine the strength of the two arising CSB contact terms by a fit to the differences of the separation energies of these hypernuclei in the $0^+$ and $1^+$ states, respectively. By construction, the resulting interaction describes all low energy hyperon-nucleon scattering data, the hypertriton and the CSB in ${^4_Λ\rm He}$-${^4_Λ\rm H}$ accurately. This allows us to provide first predictions for the $Λ$n scattering lengths, based solely on available hypernuclear data.

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arXiv2021

S-shell $ΛΛ$ hypernuclei based on chiral interactions

We generalize the Jacobi no-core shell model (J-NCSM) to study double-strangeness hypernuclei. All particle conversions in the strangeness $S=-1,-2$ sectors are explicitly taken into account. In two-body space, such transitions may lead to the coupling between states of identical particles and of non-identical ones. Therefore, a careful consideration is required when determining the combinatorial factors that connect the many-body potential matrix elements and the free-space two-body potentials. Using second quantization, we systematically derive the combinatorial factors in question for $S=0,-1,-2$ sectors. As a first application, we use the J-NCSM to investigate $ΛΛ$ s-shell hypernuclei based on hyperon-hyperon (YY) potentials derived within chiral effective field theory at leading order (LO) and up to next-to-leading order (NLO). We find that the LO potential overbinds $^{\text{ }\text{ }\text{ } \text{}6}_{ΛΛ}\text{He}$ while the prediction of the NLO interaction is close to experiment. Both interactions also yield a bound state for $^{\text{ }\text{ }\text{ } \text{}5}_{ΛΛ}\text{He}$. The $^{\text{}\text{ }\text{ }\text{}4}_{ΛΛ}\text{H}$ system is predicted to be unbound.

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