Toward new frontiers : Encounter and synergy of state-of-the-art astronomical detectors and exotic quantum beams

Program D01-3	Cosmic-ray observation using exotic atoms and applications of this new approach
Principal Investigator	FUKE, Hideyuki (JAXA)

A negatively charged particle captured by an atom forms an excited exotic atom. The exotic atom deexcites and emits the characteristic X-rays whose energies depend on the exotic atom species. By measuring these X-ray energies, the initially captured particle can be identified. This identification technique is a new approach to utilize exotic atom physics. We will examine applications of the exotic-atom-based technique to the astrophysical observations and other related fields.

A conceptual diagram of the GAPS exotic-atom technique. An anti-nucleus slows down and stops in the silicon detector forming an exotic atom. Through the deexcitation of the exotic atom, the characteristic X-rays will be emitted followed by the pions and protons emission in the nuclear annihilation. Using this technique, cosmic-ray anti-nuclei are identified. As a typical example in astrophysics, the exotic-atom technique will be utilized to search for rare anti-nuclei in the cosmic radiation. Heavy cosmic-ray anti-nuclei, such as antideuteron and antihelium, are still undiscovered but can be produced by dark matter or primordial black holes. These unrevealed astrophysical subjects will be newly probed by a highly sensitive survey of the cosmic-ray anti-nuclei. The GAPS (General Anti-Particle Spectrometer) experiment first plans to apply the exotic-atom technique to the cosmic-ray anti-nuclei observation. In this research we will seek a possibility to upgrade the present instrument design to evolve GAPS in the future. To meet this scope, we will develop the lithium-drifted silicon detector, which functions as a target to form an exotic atom and as a key detector to measure the characteristic X-rays. We will also develop a numerical simulation of the instrument to further increase the observation sensitivity. These developments for the exotic-atom technique will be applied to researches in the other fields.

Members

Reference Materials

• M. Kozai, H. Fuke, M. Yamada et al., “Developing a mass-production model of large-area Si(Li) detectors with high operating temperatures,” arXiv:1906.05577 .
• F. Rogers, M. Xiao, K. M. Perez et al., “Large-area Si(Li) detectors for X-ray spectrometry and particle tracking in the GAPS experiment,” arXiv:1906.00054 .
• K. Perez, T. Aramaki, C. J. Hailey et al., “Fabrication of low-cost, large-area prototype Si(Li) detectors for the GAPS experiment,” Nucl. Instrum. Methods Phys. Res. A 905, 12–21 (2018), DOI: 10.1016/j.nima.2018.07.024 .
• T. Aramaki, S. Boggs, S. Bufalino et al., “Review of the theoretical and experimental status of dark matter identification with cosmic-ray antideuterons,” Phys. Rep. 618, 1–37 (2016), DOI: 10.1016/j.physrep.2016.01.002 .
• T. Aramaki, C. J. Hailey, S. E. Boggs et al., “Antideuteron Sensitivity for the GAPS Experiment,” Astropart. Phys. 74, 6–13 (2016), DOI: 10.1016/j.astropartphys.2015.09.001 .