TES application to kaonic atom X-ray spectroscopy in a charged-particle beamline

荷電粒子ビームラインでのK中間子原子X線分光へのTESの応用

橋本 直*   ; 谷田 聖   ; 他49名*

Hashimoto, Tadashi*; Tanida, Kiyoshi; 49 of others*

We are developing a new technique to study the strong interaction between a hadron and an atomic nucleus: high-resolution TES-based X-ray spectroscopy of hadronic atoms. The strong interaction induces a shift and broadening of the atomic energy levels from their purely electromagnetic values. Thus, precise measurements of the X-ray-emission lines of a hadronic atom can reveal the hadron-nucleus strong interaction at zero kinetic energy. Presently, we are preparing to measure the - X-ray lines of kaonic helium-3 and helium-4 (6.2 keV and 6.4 keV, respectively) at the Japan Proton Accelerator Research Complex (J-PARC; Tokai, Japan). If we determined the strong-force shift in the helium 2p orbital to a precision of 0.2 eV, we could distinguish between the two leading antikaon-nucleus strong-interaction models. Here, we plan to use a 240-pixel TES array of about 23 mm collecting area with 4 m thick Bi absorbers. Our project represents the first attempt to use a TES-based X-ray spectrometer in a charged-particle beamline, and we have identified some challenges: (1) energy resolution is deteriorated by charged-particle passages; (2) a continuum background in the X-ray spectrum is generated by charged particles; (3) the science X-ray yield is expected to be very low, at 200 counts per week for the kaonic-helium-atom experiment. Here we present the status of our project.