Search for the Axion-Like-Particles in the $\eta\to\pi^{+}\pi^{-}e^{+}e^{-}$ decay with HADES detector

TL;DR

This paper reports a search for Axion-Like-Particles in eta meson decays using the HADES detector, aiming to identify potential new particles that could explain phenomena beyond the Standard Model.

Contribution

The study introduces a novel analysis strategy to search for ALPs in eta decay channels using high-statistics data from the HADES detector.

Findings

No resonant peak observed in the dilepton invariant mass spectrum.

Established upper limits on the coupling strength of ALPs in the studied decay channel.

Developed a method for event selection and particle identification in this context.

Abstract

The dark matter and existence of new particles are now a possible explanation of several physics phenomena which evade the predictions of the Standard Model. In this context Axion-Like-Particles (ALP) with masses in the MeV to GeV range with additional Peccei-Quinn breaking contribution, and which are coupled to the Standard Model have been postulated. To search for the existence of such new particles, we have launched dedicated analysis of a high statistics data sample collected by High-Acceptance Di-Electron Spectrometer (HADES) operating at GSI in Darmstadt. In particular, we study $\eta$ meson decays into $\pi^{+}\pi^{-}e^{+}e^{-}$, where hypothesized isoscalar gauge boson $a$ could be produced in the intermediate state $\eta\to\pi^{+}\pi^{-}a$ decaying predominantly to $e^{+}e^{-}$. In this report we describe the analysis strategy we applied to search for a resonant peak in the dilepton invariant mass spectrum $\eta\to\pi^{+}\pi^{-}a\to \pi^{+}\pi^{-}e^{+}e^{-}$ and present the method for event selection and particle identification.