High resolution spectroscopy of Ξ hypernuclei (J-PARC E70)

Understanding of the strong force has been extended from the nuclear interaction to the baryon-baryon interaction with strangeness degrees of freedom (S) by investigating hypernuclear energy structures. There is few spectroscopic information on S = −2 hypernuclei such as double-Λ and Ξ hypernuclei than those of Λ and Σ hypercuclei (S = −1). Recently, a few Ξ hypernuclear events have been reported from emulsion experiments. Also the data of femtoscopy from the ALICE Collaboration show that the ΞN and double-Λ interactions are attractive. To further study the ΞN interation, spectroscopic experiment of Ξ hypernuclei would play an indispensable role.

We are going to perform a high-resolution spectroscopy of ¹²_ΞBe hypernuclei by a missing-mass method via the ¹²C(K⁻, K⁺) reaction (J-PARC E70). The experiment will be carried out at the J-PARC K1.8 beamline, which provides a high-intensity K⁻ beam, with a newly constructed high-resolution magnetic spectrometer S-2S. An active fiber target (AFT) will be used as an experimental target. The expected statistics and missing-mass resolutions are about 100 counts and 2 MeV/c²(FWHM), respectively, which enable us to investigate the structure of Ξ hypernuclei with a higher signal sensitivity than previous experiments.

In June 2023, the first commissioning run of J-PARC E70 was carried out, and a part of calibration data for S-2S and AFT were successfully taken.

In this talk, we will report the analysis results of the first commissioning run and the prospects of the J-PARC E70.