Applying New Physics to the Problems of the \(\eta′\to\pi^0\gamma\gamma\) Decay

Abstract

Rare decays of light mesons may be a discovery window for a new weakly coupled forces hidden at a low-energy QCD scale. BES-III Collaboration reported an observation of the rare decay \(\eta' \to\pi^0\gamma\gamma\). The observed decay width disagrees with the preliminary theoretical estimates. We show that this tension may be attributed to New Physics, presumably Dark Photon. For completeness, we consider a possible influence of New Physics on a similar well-measured decay \(\eta \to\pi^0\gamma\gamma\) and a recently measured one, \(\eta' \to\eta\gamma\gamma\), showing that the impact of the hypothetical Dark Photon may be also present in these decays.

Keywords

• Dark Photon
• Rare Decays
• VMD
• ChPT
• LσM
• unitarity conditions