HYP2018: 13th International Conference on Hypernuclear and Strange Particle Physics

High-resolution spectroscopic study of the $\Xi$-hypernuclei with S-2S spectrometer

Not scheduled

15m

2nd Floor

Abstract Submission

Speaker

Mr Takuya Nanamura (Kyoto University)

Description

Spectroscopic study of $\Xi$-hypernuclei provides insights into the $\Xi$-$N$ interaction and the $\Xi N \to \Lambda \Lambda$ coupling strength. A missing mass spectroscopy of the $\Xi$-hypernuclei was performed via the $^{12}$C$(K^-,K^+)$ reaction at J-PARC K1.8 beam line in 2015, as a pilot experiment of J-PARC E05. In this measurement, existing magnetic spectrometers, K1.8 beam line spectrometer and SKS, were used for $K^-$ and $K^+$ momentum reconstruction. These spectrometers had momentum resolutions of $\Delta p$/$p <1.0 \times 10^{-3}$ (FWHM) and $\Delta p$/$p =3.0 \times 10^{-3}$ (FWHM), respectively. We have achieved the missing mass resolution 5.4 MeV (FWHM) which is the best resolution in the $\Xi$-hypernuclear missing mass studies. It is important to achieve a better missing mass resolution of 2 MeV (FWHM) to observe the $^{12}_{\Xi}\text{Be}$ structure including core excitations. As the next step, we are constructing a new spectrometer S-2S (Strangeness -2 Spectrometer) for the $K^+$, with an improved momentum resolution of 5 $\times 10^{-4}$. In this condition, the total missing-mass resolution would be affected mainly due to the target energy loss straggling when we use a thick target to enhance the production. To reduce energy loss straggling in the target, we are developing an active target composed of about 1000 scintillating fibers of $\phi$ 3 mm. This active fiber-target system enables us to correct energy loss of $K^-$ and $K^+$ event by event. Construction of the magnets and most parts of detectors for S-2S has been completed. It will soon be ready for installation in J-PARC K1.8 beam line. In this presentation, an overview of the $\Xi$-hypernuclear experiment with S-2S will be introduced. In addition, we present the development of a water Cherenkov detector and an active fiber target in detail.