The ASACUSA CUSP collaboration at the Antiproton Decelerator (AD) of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. We ...describe here the latest developments on the spectroscopy apparatus developed to be coupled to the antihydrogen production setup (CUSP).
The SIDDHARTA experiment measured the kaonic 3He and 4He 3d →2p X-ray transitions using gaseous targets for the first time. The strong-interaction shift both of the kaonic 3He and 4He 2p states was ...determined with a precision of a few eV. The shift of kaonic 4He is much smaller than the values obtained in the experiments performed in 70’s and 80’s, while it is consistent with the recent result of the KEK E570 experiment, as well as the theoretical calculated values. Therefore, the problem on kaonic helium (the “kaonic helium puzzle”) was definitely solved. The first observation of the kaonic 3He X-rays was also achieved in the SIDDHARTA experiment. The shift both of kaonic 3He and 4He was found to be as small as a few eV.
The kaonic 3He and 4He X-rays emitted in the 3d-2p transitions were measured in the SIDDHARTA experiment. The widths of the kaonic 3He and 4He 2p states were determined to be Gamma_2p(3He) = 6 \pm 6 ...(stat.) \pm 7 (syst.) eV, and Gamma_2p(4He) = 14 \pm 8 (stat.) \pm 5 (syst.) eV, respectively. Both results are consistent with the theoretical predictions. The width of kaonic 4He is much smaller than the value of 55 \pm 34 eV determined by the experiments performed in the 70's and 80's, while the width of kaonic 3He was determined for the first time.
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