Development of large acceptance spectrometer for systematic study of kaonic nuclei at J-PARC

Nanamura, Takuya; Hashimoto, Tadashi   ; Sakuma, Fuminori*; Yamaga, Takumi*; Iwasaki, Masahiko*

Bound states caused by attractive interaction, such as and kaonic nuclei, are interesting systems with strangeness. Many experimental attempts have tried to establish an existence of the lightest kaonic nuclei, "". However, no clear conclusion was reached. Recently, J-PARC E15 collaboration searched for "", using the in-flight He reaction with an exclusive analysis of the final state. By reconstructing not only the invariant-mass but also momentum transfer to the system, they definitely showed event concentration interpreted as "" bound state. Moreover, small spatial size of "" is implied. In order to expand this successful experimental method to heavier kaonic nuclei, such as , and detailed study for fundamental properties of the state, we are developing a new magnetic spectrometer. Because an exclusive analysis requires detections of decay particles from the kaonic nuclei as many as possible, the new spectrometer will have larger solid angle of 93%. To realize it, superconducting solenoid magnet and some detectors, a cylindrical drift chamber and charged particle/neutron counters, are 3-4 meters long. Detection efficiencies for neutron would be improved at least 1.7 times better than current spectrometer. In this presentation, I will talk about designs and development status of the new large acceptance spectrometer.