Speaker
Description
Charge symmetry breaking (CSB) in the mirror $^4_\Lambda {\rm H} - ^4_\Lambda {\rm He}$ hypernuclei has been known for decades. Recent experimental measurements [1,2] confirmed the large CSB splitting in the corresponding $0^+$ states $\Delta B(0^+) = 233 \pm 92$~keV while the experimental value for the $1^+$ excited states $\Delta B(1^+) = -83 \pm 94$~keV allows a change of sign, being compatible with zero. Theoretically, it was suggested by Dalitz and von Hippel (DvH) that large hypernuclear CSB might be generated through OPE contribution by allowing $\Lambda - \Sigma^0$ mixing in $SU(3)_f$ flavor octet [3]. This mechanism was later generalized by Gal [4] and used in a study of the 4-body hypernuclear CSB using $\chi$EFT(LO) $\Lambda N$ interaction [5,6]. A rather different approach was adopted in Refs. [7,8] where hypernuclear CSB was introduced through a contact interaction fitted to the experimental $\Delta B(0^+)$ and $\Delta B(1^+)$ splittings. Interestingly, within the LO pionless effective field theory it was found that the CSB interaction fitted to these
energies might be linked through partially conserved baryon-baryon $SU(3)_f$ symmetry back to the DvH mechanism [9]. In my talk, I will review these works in order to give a general overview of the current status.
[1] T. O. Yamamoto et al. (J-PARC E13 Collaboration), Phys. Rev. Lett., 115, 222501 (2015).
[2] A. Esser et al. (MAMI A1 Collaboration), Phys. Rev. Lett. 114, 232501 (2015); F. Schulz et al. (MAMI A1 Collaboration), Nucl. Phys. A 954, 149 (2016).
[3] R. H. Dalitz and F. von Hippel, Phys. Lett 10, 153 (1964).
[4] A. Gal, Phys. Lett. B 744, 352 (2015).
[5] D. Gazda and A. Gal, Phys. Rev. Lett. 116, 122501 (2016).
[6] D. Gazda and A. Gal, Nucl. Phys. A 954 161 (2016).
[7] J. Haidenbauer, U.-G. Meissner, and A. Nogga, Few-Body Syst. 62, 105 (2021).
[8] H. Le, J. Haidenbauer, U.-G. Meissner, and A. Nogga, Phys. Rev. C 107, 024002 (2023).
[9] M. Sch\"{a}fer, N. Barnea, and A. Gal, Phys. Rev. C 106, L031001 (2022).
