Status of the X17 search with the MEG II apparatus

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The MEGII experiment at PSI July 2024

Status of the X17 search with the MEG II apparatus
The MEGII experiment at PSI July 2024

Description

A resonant structure has been observed at ATOMKI in the invariant mass of electron-positron pairs, interpreted as the production of a hypothetical particle (X17).

The MEG II apparatus at PSI, designed to search for the μ+ → e+ γ, can perform also the X17 search.

Protons from a CW accelerator, with an energy up to 1 MeV, was delivered on a dedicated Li-based targets (with thicknesses up to several μm) and the 7Li(p,e+e−)8Be process studied using the MEG II spectrometer. This aims to reach a better invariant mass resolution than the previous experiments and to study the production of the X17 with a larger acceptance and therefore to shed more light on the nature of this observation.

After a 2022 engineering run, a physics run took place in 2023, during which the first data sample was collected. We report on the status of this search with the MEG II apparatus, presenting the collected data, the analysis strategy, and the current results.

https://indico.cern.ch/event/1291157/contributions/5887844/

pdf here

https://indico.cern.ch/event/129115...ts/2900132/5085565/MEGII_X17_ICHEP2024_AP.pdf

could an experimental physicist explains the data and results ?

also included

Implications of X17 boson to \(D\) meson, Charmonium, and \(\phi\) meson decays​

Description

The recent ATOMKI experiments provided evidence pointing towards the existence of an X17 boson in the anomalous nuclear transitions of Beryllium-8, Helium-4, and Carbon-12. The favored ranges for X17 boson couplings to u and d quarks are determined through fittings to these nuclear transitions. In this work, we consider X17 boson contributions to the previously measured
meson decays, including
and , as well as the measured decays of and . Using these data, we perform an independent fitting to the couplings between the X17 boson and various flavors of quarks. This fitting requires a huge X17 boson coupling to the u quark that creates a serious tension with ATOMKI's data. Our analysis models X17 as a vector boson and allows its quark couplings to be generation dependent. The implications of our findings are discussed.

https://indico.cern.ch/event/1291157/contributions/5887839/

https://indico.cern.ch/event/129115...9/attachments/2899364/5084052/Oral_ICHEP .pdf