Speaker
Description
Kaonic atoms, exotic systems in which a negatively charged kaon replaces an electron, provide a unique laboratory for probing both the strong and electromagnetic interactions. The X-ray transitions emitted during their atomic cascade are modified by the strong interaction in the innermost levels, enabling precision studies of kaon–nucleon and kaon–nucleus interactions and offering direct access to non-perturbative QCD in the strangeness sector.
More than four decades ago, Richard Henry Dalitz emphasized that ``the most important experiment to be carried out in low-energy $K$-meson physics is the definitive determination of the energy-level shifts in $K^-p$ and $K^-d$ atoms, because of their direct connection to the physics of $\bar{K}N$ interaction and their complete independence from all other kinds of measurements which bear on this interaction''. Despite the fundamental importance of the kaonic deuterium measurement, its extreme experimental difficulty has long prevented its realization—until now. The SIDDHARTA-2 collaboration, exploiting the high-quality low-energy kaon beam at the DAΦNE collider in Frascati (Italy) and fast, high-resolution Silicon Drift Detectors (SDDs), has performed the first high-precision X-ray spectroscopy of kaonic deuterium, determining the energy shift and width induced by the strong interaction in the 1s atomic level. These results provide unprecedented constraints on the antikaon–deuteron interaction at threshold energy and advance our understanding of non-perturbative strong interactions in the strangeness sector. In addition, the collaboration has measured transitions in kaonic neon and fluorine, governed predominantly by quantum electrodynamics (QED), providing a unique opportunity to test bound-state QED under extreme electromagnetic fields.
In this contribution, I will present the experimental approach, the unique challenges of measuring kaonic deuterium, and the latest results from SIDDHARTA-2. I will discuss their implications for the low-energy strong interaction and outline future perspectives for systematic kaonic atom measurements at DAΦNE and J-PARC, supported by next-generation X-ray detector technologies.
| Theoretical or experimental | Experimental |
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