# Ab initio calculations for non-strange and strange few-baryon systems

## TL;DR

This paper employs ab initio methods to accurately calculate low-energy spectra and resonance properties of non-strange and strange baryon systems, enhancing the precision of astrophysical and hypernuclear data.

## Contribution

It introduces a modified hyperspherical harmonics basis for improved resolution in LIT calculations, enabling more precise determination of astrophysical S-factors and hypernuclear binding energies.

## Key findings

- High-precision calculations of helium isotopes spectra
- Enhanced LIT resolution with modified HH basis
- Consistent hypernuclear binding energy results

## Abstract

Concerning the non-strange particle systems the low-energy excitation spectra of the three- and four-body helium isotopes are studied. Objects of the study are the astrophysical $S$-factor $S_{12}$ of the radiative proton deuteron capture $d(p,\gamma)^3$He and the width of the $^4$He isoscalar monopole resonance.Both observables are calculated using the Lorentz integral transform (LIT) method. The LIT equations are solved via expansions of the LIT states on a specifically modified hyperspherical harmonics (HH) basis. It is illustrated that at low energies such a modification allows to work with much higher LIT resolutions than with an unmodified HH basis. It is discussed that this opens up the possibility to determine astrophysical $S$-factors as well as the width of low-lying resonances with the LIT method. In the sector of strange baryon systems binding energies of the hypernucleus $^3_\Lambda$H are calculated using a nonsymmetrized HH basis. The results are compared with those calculated by various other groups with different methods. For all the considered non-strange and strange baryon systems it is shown that high-precision results are obtained.