27 June 2022 to 1 July 2022
Prague, Czech Republic
Europe/Zurich timezone

Newly completed JLab experiment (E12-17-003): Determine the unknown Λn interaction by investigating the possible Λnn resonance

27 Jun 2022, 12:40
20m
Hotel Pyramida

Hotel Pyramida

talk 1; Mon-II

Speaker

Prof. Liguang Tang (Hampton University/JLab)

Description

Direct $\Lambda n$ scattering data is extremely important and needed based on the newly confirmed Charge-Symmetry-Breaking (CSB) at a level of ~270 keV from the binding energy difference observed between ground states of $^4_{\Lambda}$He and $^4_{\Lambda}$H. Especially, the $\Lambda n$ data does not exist at all, thus the properties of $\Lambda n$ interaction has been assumed to be identical to that of $\Lambda p$ interaction. The resonance of $\Lambda nn$ system, if it does exist, may provide a unique and the only experimental data that can be used to determine the unknown properties of $\Lambda n$ interaction [1].

Because the $^3{\rm H}(e, e’K^+)(\Lambda nn)$ reaction is unique for studying the possible neutral $Ynn$ systems, a mass spectroscopy experiment (E12-17-003) with a pair of nearly identical high resolution spectrometers and a tritium target was performed in Hall A at Jefferson Lab. Although the experimental condition with the existing apparatus was not optimized for production of hypernuclei, enhancements, which may correspond to a possible $\Lambda nn$ resonance and a pair of $\Sigma NN$ states, were observed with an energy resolution of about 1.21~MeV $(\sigma)$. Since the statistics is low, definitive identifications cannot be made. However, the result is definitely interesting and an optimized experiment for further investigation with much improved statistics is needed.

In addition, although bound A = 3 [2, 3] and 4 $\Sigma$-hypernuclei have been predicted, only an A = 4 $\Sigma$-hypernucleus ($^4_{\Sigma}He$) was found [4], utilizing the $(K^-, \pi^-)$ reaction on a $^4$He target. The possible bound $\Sigma NN$ state is likely a $\Sigma^0 nn$ state, although this has to be confirmed by future experiments.

Reference
[1] I. R. Afnan and B. F. Gibson, Phys. Rev. C 92, 054608 (2015).
[2] I. R. Afnan and B. F. Gibson, Phys. Rev. C 47, 1000 (1993).
[3] T. Harada and Y. Hirabayashi, Phys. Rev. C 89, 054603 (2014).
[4] T. Nagae, T. Miyachi, T. Fukuda, H. Outa, T. Tamagawa, J. Nakano, et al., Phys. Rev. Lett. 80, (1998) 1605-1609.

Primary author

Prof. Liguang Tang (Hampton University/JLab)

Presentation materials