arXiv subjects

J. Haidenbauer

Publications and source records attributed to J. Haidenbauer.

At least 19 recordsLinked to original sources

arXiv2025

Hadron Physics Opportunities at FAIR

This White Paper outlines a coordinated, decade-spanning programme of hadron and QCD studies anchored at the GSI/FAIR accelerator complex. Profiting from intense deuteron, proton and pion beams coupled with high-rate capable detectors and an international theory effort, the initiative addresses fundamental questions related to the strong interaction featuring confinement and dynamical mass generation. This includes our understanding of hadron-hadron interactions and the composition of hadrons through mapping the baryon and meson spectra, including exotic states, and quantifying hadron structure. This interdisciplinary research connects topics in the fields of nuclear, heavy-ion, and (nuclear) astro (particle) physics, linking, for example, terrestrial data to constraints on neutron star structure. A phased roadmap with SIS100 accelerator start-up and envisaged detector upgrades will yield precision cross sections, transition form factors, in-medium spectral functions, and validated theory inputs. Synergies with external programmes at international accelerator facilities worldwide are anticipated. The programme is expected to deliver decisive advances in our understanding of non-perturbative (strong) QCD and astrophysics, and high-rate detector and data-science technology.

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arXiv2024

Neutron Star Properties and Femtoscopic Constraints

We construct the equation of state of hypernuclear matter and study the structure of neutron stars employing a chiral hyperon-nucleon interaction of the J\"{u}lich--Bonn group tuned to femtoscopic $\Lambda p$ data of the ALICE Collaboration, and $\Lambda\Lambda$ and $\Xi$N interactions determined from lattice QCD calculations by the HAL QCD Collaboration that reproduce the femtoscopic $\Lambda\Lambda$ and $\Xi^-p$ data. We employ the ab-initio microscopic Brueckner--Hartree--Fock theory extended to the strange baryon sector. A special focus is put on the uncertainties of the hyperon interactions and how they are effectively propagated to the composition, equation of state, mass-radius relation and tidal deformability of neutron stars. To such end, we consider the uncertainty due to the experimental error of the femtoscopic $\Lambda p$ data used to fix the chiral hyperon-nucleon interaction and the theoretical uncertainty, estimated from the residual cut-off dependence of this interaction. We find that the final maximum mass of a neutron star with hyperons is in the range $1.3-1.4$ $M_\odot$, in agreement with previous works. The hyperon puzzle, therefore, remains still an open issue if only two-body hyperon-nucleon and hyperon-hyperon interactions are considered. Predictions for the tidal deformability of neutron stars with hyperons are found to be in agreement with the observational constraints from the gravitational wave event GW170817 in the mass range $1.1-1.3$ $M_\odot$.

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arXiv2024

$p\barΛ$ final-state interaction in the reactions $e^+e^- \to K^- p \bar Λ$ and $J/ψ\to K^- p \bar Λ$

Near-threshold $p\barΛ$ mass spectra for the reactions $e^+e^- \to K^- p\barΛ$ and $J/ψ\to K^- p\barΛ$ are investigated with an emphasis on the role played by the interaction in the $p\barΛ$ system. As guideline for the $p\barΛ$ interaction a variety of $Λ\barΛ$ potential models is considered that have been established in the analysis of data on $p\bar p\to Λ\barΛ$ in the past. Arguments why the properties of the $p\barΛ$ and $Λ\barΛ$ interactions can be expected to be very similar are provided. It is shown that the near-threshold enhancement in the invariant mass observed for the $e^+e^-$ reaction can be reproduced quantitatively by the assumed $p\barΛ$ final-state interaction in the partial wave suggested by an amplitude analysis of the experiment. The effect of the $p\barΛ$ final-state interaction in other decays is explored, including the recently measured reactions $B^- \to J/ψ\, \bar p Λ$ and $B^+ \to J/ψ\, p \barΛ$. It is found that the final-state interaction improves the description of the measured invariant mass near threshold in most cases.

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arXiv2023

Constraining the p{\Lambda} interaction from a combined analysis of scattering data and correlation functions

This work provides the first combined analysis of low-energy p$\Lambda$ scattering, considering both cross section and correlation data. The obtained results establish the most stringent constraints to date on the two-body p$\Lambda$ interaction, pointing to a weaker attraction than so far accepted. The best set of scattering lengths for the spin singlet and triplet are found to range from $f_0, f_1 = (2.1, 1.56)$ to $(3.34, 1.18)~$fm. With a chiral NY potential fine-tuned to those scattering parameters, the in-medium properties of the $\Lambda$ are explored and a potential depth of $U_\Lambda= -36.3\pm 1.3 \mathrm{(stat)}^{+2.5}_{-6.2}\mathrm{(syst)}$ MeV is found at nuclear matter saturation density.

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arXiv2022

Status of the hyperon-nucleon interaction in chiral effective field theory

The Jülich-Bonn group aims at an extensive study of the baryon-baryon ($BB$) interaction involving strange baryons ($Λ$, $Σ$, $Ξ$) within SU(3) chiral effective field theory. An overview of achievements and new developments over the past few years is provided. The topics covered are: 1) Derivation of the leading charge-symmetry breaking (CSB) interaction for the $ΛN$ system and its application in a study of CSB effects in $A$=$4$ $Λ$-hypernuclei. 2) Updated results for the $ΞN$ interaction at NLO and predictions for $Ξ^- p$ correlation functions. 3) Extension of the $ΛN$-$ΣN$ interaction to next-to-next-to-leading order.

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arXiv2022

Exploring the $Σ^+ p$ interaction by measurements of the correlation function

The spin-dependent components of the fundamental hyperon-nucleon interactions are largely unknown. We show that under reasonable assumptions, a measurement of the $Σ^+ p$ correlation function in high-energy proton-proton or heavy-ion collisions combined with cross section data allows to separate the singlet and the triplet $S$-wave contributions.

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arXiv2022

Conceptual design of the Spin Physics Detector

The Spin Physics Detector, a universal facility for studying the nucleon spin structure and other spin-related phenomena with polarized proton and deuteron beams, is proposed to be placed in one of the two interaction points of the NICA collider that is under construction at the Joint Institute for Nuclear Research (Dubna, Russia). At the heart of the project there is huge experience with polarized beams at JINR. The main objective of the proposed experiment is the comprehensive study of the unpolarized and polarized gluon content of the nucleon. Spin measurements at the Spin Physics Detector at the NICA collider have bright perspectives to make a unique contribution and challenge our understanding of the spin structure of the nucleon. In this document the Conceptual Design of the Spin Physics Detector is presented.

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arXiv2022

Strangeness ${S=-3}$ and ${-4}$ baryon-baryon interactions in chiral effective field theory

Studies of the baryon-baryon interaction involving hyperons within chiral effective field theory, so far performed up to next-to-leading order (NLO) in the chiral expansion, have shown that for the strangeness $S=-1$ ($ΛN$, $ΣN$) and $S=-2$ ($ΛΛ$, $ΞN$) sectors a consistent and satisfactory description of the available scattering data and experimental constraints can be achieved based on the assumption of broken SU(3) flavor symmetry. We explore the possible extension of this approach at the NLO level to strangeness $S=-3$ and $S=-4$ baryon-baryon systems where empirical information is rather scarce. Specifically we address the question how measurements of two-body correlation functions in heavy-ion collisions and/or in high-energetic proton-proton collisions can help to constrain the interaction in channels like $ΞΛ$ or $ΞΞ$.

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arXiv2021

On the structure in the $ΛN$ cross section at the $ΣN$ threshold

The complexity of threshold phenomena is exemplified on a prominent and long-known case - the structure in the $Λp$ cross section (invariant mass spectrum) at the opening of the $ΣN$ channel. The mass splitting between the $Σ$ baryons together with the angular momentum coupling in the $^3S_1$-$^3D_1$ partial wave imply that, in principle, up to six channels are involved. Utilizing hyperon-nucleon potentials that provide an excellent description of the available low-energy $Λp$ and $ΣN$ scattering data, the shape of the resulting $Λp$ cross section is discussed and the poles near the $ΣN$ threshold are determined. Evidence for a strangeness $S=-1$ dibaryon is provided, in the form of a deuteron-like (unstable) $ΣN$ bound state. Predictions for level shifts and widths of $Σ^-p$ atomic states are given.

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arXiv2021

Comment on "$Λ_c N$ interaction in leading order covariant chiral effective field theory"

Song et al. [Phys. Rev. C 102, 065208 (2020)] presented results for the $Λ_c N$ interaction based on an extrapolation of lattice simulations by the HAL QCD Collaboration at unphysical quark masses to the physical point via covariant chiral effective field theory. We point out that their predictions for the $^3D_1$ partial wave disagree with available lattice results. We discuss the origin of that disagreement and present a comparison with predictions from conventional (non-relativistic) chiral effective field theory.

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arXiv2020

Spin observables of proton-deuteron elastic scattering at SPD NICA energies within the Glauber model and pN amplitudes

A systematic analysis of nucleon-nucleon scattering amplitudes is available up to a laboratory energy of $3$~GeV in case of the $pp$ system and up to $1.2$ GeV for $pn$. At higher energies there is only incomplete experimental information on $pp$ elastic scattering, whereas data for the $pn$ system are very scarce. We apply the spin-dependent Glauber theory to calculate spin observables of $pd$ elastic scattering at $3$-$50$ GeV/c using $pp$ amplitudes available in the literature and parametrized within the Regge formalism. The calculated vector $A_y^p$, $A_y^d$ and tensor $A_{xx}$, $A_{yy}$ analyzing powers and the spin-correlation coefficients $C_{y,y}$, $C_{x,x}$, $C_{yy,y}$, $C_{xx,y}$ can be measured at SPD NICA and, thus, will provide a test of the used $pN$ amplitudes.

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arXiv2020

Exploring the $Λ$-deuteron interaction via correlations in heavy-ion collisions

$Λ$-deuteron two-particle momentum correlation functions, to be measured in high-energy heavy-ion collisions, are investigated. In particular, the question is addressed whether such correlations can serve as an additional and alternative source of information on the elementary $ΛN$ interaction. The study is performed within the Lednicky-Lyuboshits formalism, utilizing an effective range expansion for the two relevant $S$-wave $Λd$ amplitudes with parameters taken from the literature. It is found that in collisions characterized by a large emitting source the $Λd$ correlation function is predominatly sensitive to the quartet state ($^4S_{3/2}$). In contrast, for small source sizes the contribution from the doublet partial wave ($^2S_{1/2}$) could be significant. Though the latter is constrained by the hypertriton binding energy, its present experimental uncertainty impedes an accurate determination of the doublet amplitude and, in turn, complicates conclusions on the quartet state.

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arXiv2020

Femtoscopic correlations and the $Λ_c N$ interaction

We study the prospects for deducing constraints on the interaction of charmed baryons with nucleons from measurements of two-particle momentum correlation functions for $Λ_c p$. The correlation functions are calculated for $Λ_c N$ and $Σ_c N$ interactions that have been extrapolated from lattice QCD simulations at unphysical masses of $m_π=410-570$ MeV to the physical point using chiral effective field theory as guideline. In addition, we consider phenomenological $Y_c N$ models from the literature to explore the sensitivity of the results to the properties of the interaction in detail. We find that a measurement of the $Λ_c p$ correlation functions could indeed allow one to discriminate between strongly attractive $Λ_c N$ forces, as predicted by some phenomenological models, and a weakly attractive interaction as suggested by the presently available lattice simulations.

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arXiv2019

Kaon Photoproduction and the $Λ$ Decay Parameter $α_-$

The weak decay parameter $α_-$ of the $Λ$ is an important quantity for the extraction of polarization observables in various experiments. Moreover, in combination with $α_+$ from $\barΛ$ decay it provides a measure for matter-antimatter asymmetry. The weak decay parameter also affects the decay parameters of the $Ξ$ and $Ω$ baryons and, in general, any quantity in which the polarization of the $Λ$ is relevant. The recently reported value by the BESIII collaboration of $0.750(9)(4)$ is significantly larger than the previous PDG value of $0.642(13)$ that had been accepted and used for over 40 years. In this work we make an independent estimate of $α_-$, using an extensive set of polarization data measured in kaon photoproduction in the baryon resonance region and constraints set by spin algebra. The obtained value is 0.721(6)(5). The result is corroborated by multiple statistical tests as well as a modern phenomenological model, showing that our new value yields the best description of the data in question. Our analysis supports the new BESIII finding that $α_-$ is significantly larger than the previous PDG value. Any experimental quantity relying on the value of $α_-$ should therefore be re-considered.

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arXiv2019

Hyperon-nucleon interaction within chiral effective field theory revisited

The $ΛN$ and $ΣN$ interactions are considered at next-to-leading order in SU(3) chiral effective field theory. Different options for the low-energy constants that determine the strength of the contact interactions are explored. Two variants are analysed in detail which yield equivalent results for $ΛN$ and $ΣN$ scattering observables but differ in the strength of the $ΛN \to ΣN$ transition potential. The influence of this difference on predictions for light hypernuclei and on the properties of the $Λ$ and $Σ$ hyperons in nuclear matter is investigated and discussed. The effect of the variation in the potential strength of the $ΛN$-$ΣN$ coupling (also called $Λ-Σ$ conversion) is found to be moderate for the considered $^3_Λ\rm H$ and $^4_Λ\rm He$ hypernuclei but sizable in case of the matter properties. Further, the size of three-body forces and their relation to different approaches to hypernuclear interactions is discussed.

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arXiv2019

Phenomenological view on baryon-baryon potentials from lattice QCD simulations

A qualitative discussion on the range of the potentials as they result from the phenomenological meson-exchange picture and from lattice simulations by the HAL QCD Collaboration is presented. For the former pion- and/or $η$-meson exchange are considered together with the scalar-isoscalar component of correlated $ππ/K \bar K$ exchange. It is observed that the intuitive expectation for the behavior of the baryon-baryon potentials for large separations, associated with the exchange of one and/or two pions, does not always match with the potentials extracted from the lattice simulations. Only in cases where pion exchange provides the longest ranged contribution, like in the $ΞN$ system, a reasonable qualitative agreement between the phenomenological and the lattice QCD potentials is found for baryon-baryon separations of $r \gtrsim 1$ fm. For the $ΩN$ and $ΩΩ$ interactions where isospin conservation rules out one-pion exchange a large mismatch is observed, with the potentials by the HAL QCD Collaboration being much longer ranged and much stronger at large distances as compared to the phenomenological expectation. This casts some doubts on the applicability of using these potentials in few- or many-body systems.

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arXiv2018

Scattering of charmed baryons on nucleons

Chiral effective field theory is utilized for extrapolating results on the $Λ_c N$ interaction, obtained in lattice QCD at unphysical (large) quark masses, to the physical point. The pion-mass dependence of the components that constitute the $Λ_c N$ potential up to next-to-leading order (pion-exchange diagrams and four-baryon contact terms) is fixed by information from lattice QCD simulations. No recourse to SU(3) or SU(4) flavor symmetry is made. It is found that the results of the HAL QCD Collaboration for quark masses corresponding to $m_π= 410$--$570$ MeV imply a moderately attractive $Λ_c N$ interaction at $m_π= 138$ MeV with scattering lengths of $a\approx -1$ fm for the $^1S_0$ as well as the $^3S_1$ partial waves. For such an interaction the existence of a charmed counterpart of the hypertriton is unlikely but four- and/or five-baryons systems with a $Λ_c$ baryon could be indeed bound.

hep-ph↗

arXiv2018

Coupled-channel effects in hadron-hadron correlation functions

Two-particle momentum correlation functions as measured in heavy ion collisions or in high-energetic proton-proton collisions are studied. Special emphasis is put on systems like $ΛΛ$ or $K^-p$ where effects from the coupling to other channels could be relevant. In both cases other channels open at relatively low momenta or are already open at the reaction threshold. To have a solid basis, realistic coupled-channel interactions for $ΛΛ-ΞN-ΛΣ-ΣΣ$ and $πΛ-πΣ-\bar KN$ are utilized in the actual calculations. It is found that the opening of the $ΞN$ channel leaves a trace in the $ΛΛ$ correlation function that could be detectable in experiments. Should the proposed $H$-dibaryon be located close to or below the $ΞN$ it will have a very pronounced effect. The presence of open channels in systems like $Ξ^- p$ or $K^-p$ does influence the correlation functions significantly at low momenta and will certainly complicate any dedicated analysis.

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