X-ray spectroscopy of kaonic atoms at the DA$\Phi$NE accelerator - SIDDHARTA/SIDDHARTA2 experiments.

Sirghi D.L. per la Collaborazione SIDDHARTA
  Venerdì 30/09   15:00 - 18:00   Edificio Psicologia 2 - Aula 3F   I - Fisica nucleare e subnucleare
The X-ray measurements of kaonic atoms play an important role for understanding the low-energy QCD in the strangeness sector. The information provided by the low-energy kaon-nucleon/nuclei interaction is accessible through the study of kaonic atoms and kaonic nuclear processes. The lightest atomic systems, namely the kaonic hydrogen and the kaonic deuterium, provide the isospin-dependent kaon-nucleon scattering lengths by measuring the X-rays emitted during their de-excitation to the 1s level. The SIDDHARTA experiment studied the X-ray transitions of 4 light kaonic atoms (H, D, 3He, and 4He) using the DA$\Phi$NE electron-positron collider at LNF (Italy). The most precise values of the shift and width of the kaonic hydrogen 1$s$ state were determined, which have been now used as fundamental information for the low-energy K-p interaction in theoretical studies. An upper limit of the X-ray yield of kaonic deuterium was derived, important for future K-d experiments. The shifts, widths and yields of the kaonic ${}^3He$ and ${}^{4}He$ 2p states were obtained, confirming the end of the "kaonic helium puzzle". Presently, a significantly upgraded setup developed by the SIDDHARTA-2 collaboration is ready to perform a precise measurement of kaonic deuterium and, afterwards, of heavier exotic atoms.