Speaker
Mr
Shuhei Hayakawa
(Osaka University)
Description
The nucleon-nucleon interaction, the nuclear force, has been studied for more than half a century.
The study of hyperon-nucleon and hyperon-hyperon interactions is necessary for understanding of general baryon-baryon interaction.
However, it is difficult to produce an intense hyperon beam due to the very short life time of hyperons.
Further, it is almost impossible to use hyperons as the target for the scattering experiment.
Even in the $S = -1$ sector such as $\Lambda N$ and $\Sigma N$, the available d\
ata is limited. As for the $S = -2$ sector such as $\Lambda \Lambda$ and $\Xi N\
$ there are few experimental data.
Double hypernuclei, which has two $\Lambda $ hyperons in one nucleus, are very important probes to study the $\Lambda \Lambda$ interaction.
The nuclear emulsion has the high position resolution of sub-$\mu$m to detect the sequential weak decays of the double hyper nuclei.
Several experiments with an emulsion have been performed to search the double hyperculei production event.
At KEK E373 experiment, one is uniquely identified as the $^6_{\Lambda \Lambda}$He.
The two-$\Lambda $ binding energy and $\Lambda $-$\Lambda$ interaction energy of $^6_{\Lambda \Lambda}$He have been measured as 6.91 $\pm$ 0.16 MeV and 0.67 $\pm$ 0.17 MeV, respectively.
The J-PARC E07 experiment is the double hypernuclei search experiment with the hybrid emulsion method at J-PARC K1.8 beam line.
$\Xi^-$ hyperons are produced in the quasi-free $p(K^-, K^+)\Xi^-$ reaction %% at $P_{K^-} = 1.8$ GeV/$c$ at a diamond target.
Double hypernuclei are produced by $\Xi^-$ hyperons captured at rest in a nuclei in an emulsion layer.
The positions and angles of the incident $\Xi^-$ hyperons on the emulsion surface are predicted with the silicon strip detector, SSD, whose position resolution is 15 $\mu$m.
The method with the combination of spectrometer and emulsion analysis, so called hybrid emulsion method, very effective in saving time to search a production vertex of double hypernuclei in emulsion.
The J-PARC E07 experiment aims at accumulating 10 times higher statistics of double hypernuclei than that for KEK E373 experiment.
From $10^4$ $\Xi ^-$ hyperon captures, $10^2$ double hypernuclei would be observed and 10 double hypernuclei are uniquely identified.
The J-PARC E07 experiment have been performed in 2016 and 2017.
All of 118 modules of emulsion stacks have been irradiated and completely devel\
oped.
Primary author
Mr
Shuhei Hayakawa
(Osaka University)
Co-authors
Mr
Hiroyuki Ekawa
(Kyoto University)
Dr
Junya Yoshida
(Advanced Science Research Center, JAEA)
Dr
Masahiro Yoshimoto
(Gifu University)
Prof.
Nakazawa Kazuma
(Gifu University)
