Speaker
Description
A resonant structure has been observed at ATOMKI in the invariant mass of electron-positron pairs, produced after excitation of nuclei such as $^8$Be and $^4$He by means of proton beams. Such a resonant structure can be interpreted as the production of an hypothetical particle (X17) whose mass is around 17 MeV.
The MEG-II experiment at the Paul Scherrer Institut whose primary physics goal is the search for the charged lepton violation process $\mu \rightarrow e \gamma$ is in the position to confirm and study this observation. MEG-II employs a source of protons able to accelerate them up to a kinetic energy of about 1 MeV. This protons are absorbed on a thin target where they excite nuclear transitions to produce photons for the Xenon calorimeter calibration of the MEG-II detector.
By using a new thinner target containing $Li$ atoms the $^7$Li(p,e$^+$e$^-$)$^8$Be process is being studied with a magnetic spectrometer including a cylindrical drift chamber and a system of fast scintillators. This aims to reach a better invariant resolution of previous experiments and to study the production of the X17.
A first dedicated data-taking period in 2022 was conducted where the first internal pair creation events were observed. We report about the first results of the study of the X17 particle.
| In-person participation | Yes |
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