Speaker
Description
One key quantity for better constraining the contributions of hyperons to the equation of state of neutron matter is the $\Lambda$-neutron interaction. In absence of $\Lambda$-neutron scattering data, isospin symmetry is usually assume and interactions are determined by fitting to $\Lambda$-proton data.
But charge symmetry breaking (CSB) of the $\Lambda$-nucleon interaction has been well established by the experimentally known difference of the $\Lambda$ separation energies of the mirror hypernuclei $^4_\Lambda$He and $^4_\Lambda$H [1].
In this contribution, we employ chiral hyperon-nucleon interactions including the leading CSB contributions to constrain the $\Lambda$-neutron interaction. To this aim, 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, and then predict $\Lambda$n scattering lengths[2]. Based on two version of the hyperon-nucleon interaction and next-to-leading order and using different momentum cutoffs, we also estimate uncertainties of these predictions. The impact of the possible changes of the experimental input is discussed in view of recently improved experimental results for the separation energies of $^4_\Lambda$He and $^4_\Lambda$H.
References
[1] A. Gal, E.V. Hungerford and D.J. Millener,
Rev. Mod. Phys. 88 (2016), 035004 [arXiv:1605.00557 [nucl-th]].
[2] J. Haidenbauer, U.-G. Meißner and A. Nogga, Few Body Syst. 62 (2021), 105
[arXiv:2107.01134 [nucl-th]].