NePSi 23

The search for the X17 particle with the MEG-II apparatus

16 Feb 2023, 19:00

1h 30m

Sala delle Baleari (Palazzo Gambacorti)

Poster session Poster Session and Discussion Session

Speaker

Hicham Benmansour (Istituto Nazionale di Fisica Nucleare)

Description

The angular correlation distribution of electron-positron pairs from Internal Pair Conversion emitted by excited 8Be and 4He nucleus was measured by ATOMKI. Over the expected monotonically decreasing trend was measured a significant excess which can be interpreted as the production of a hypothetical particle (X17) whose mass is around 17 MeV.

The MEG-II experiment at the Paul Scherrer Institute searches for the lepton flavour violating decay $\mu \to e\gamma$. Its apparatus has the capability to reproduce the ATOMKI measurements in order to confirm or deny such excess in an independent manner. A Cockroft-Walton accelerator is used to send 1 MeV protons on a thin lithium target in order to produce 8Be by proton capture. The 7Li(p,e+e−)8Be process can be studied with a system composed a cylindrical drift chamber and fast scintillators immersed into a magnetic field, aiming at a better invariant mass resolution than the previous experiment.

A first data-taking period was conducted in 2022 and a second one is scheduled for 2023. We report here the first results on the analysis of 2022 data.