Speaker
Description
At K1.8 beam line in the Hadron Hall of J-PARC, high-precision missing-mass spectroscopy for $\Xi$ hypernuclei ( J-PARC E70 experiment ) is in preparation. In the J-PARC E70 experiment, the high-intensity $1.8 ~{\rm GeV}/c$ $K^{-}$ meson beam will be used for production of $\Xi$ hypernuclei ($^{12}_{\Xi}$Be) via $(K^{-}, K^{+})$ reaction. A newly installed magnetic spectrometer "S-2S" has a high momentum resolution $\Delta p/p = 6.0 \times 10^{-4}$ (FWHM) which will enable high precision spectroscopy of $\Xi$ hypernuclei with energy resolution of less than 2 MeV (FWHM).
As well as the S-2S magnets, we install an active fiber target as $^{12}$C target, multi wire drift chambers (MWDC), particle-identification (PID) counters. The active fiber target consists of scintillation fibers and prevents energy straggling from getting resolution worse. MWDCs are installed at upstream and downstream sides of the S-2S magnets to detect $K^{+}$ track. Detected $K^{+}$ tracks give momenta of $K^{+}$. Not only $K^{+}$ but also a huge number of protons and $\pi^{+}$s as background events pass through S-2S. Thus we need to suppress these backgrounds with PID counters: aerogel Cherenkov counter for $\pi^{+}$ suppression, water Cherenkov counter for proton suppression and Time-of-Flight (ToF) counter for offline PID. Preparation of these detectors is currently in progress for beamtime which will begin from January 2023. In this talk, I will present detector specifications and a preparation status of the above detectors.
