Relatore
Descrizione
Recently structures in invariant mass distributions and excitation energy spectra have been attributed to triangular singularities as discussed in e.g., [1,2] and in the review by Guo et al. [3]. These singularities emerge under specific kinematic conditions when new reaction channels open up. It will be shown that a triangular singularity associated with the opening of the $\gamma p \rightarrow p a_0 \rightarrow p \pi^0 \eta$ channel can explain the observation of a structure in the $M_{p\eta}$ invariant mass distribution near 1700 MeV/c${^2}$ in the $\gamma p \rightarrow p \pi^0 \eta$ reaction [4].\newline
\noindent
[1] G.~D.~Alexeev \textit{et al.}, The COMPASS Collaboration, Phys. Rev. Lett \textbf{127}, 082501 (2021)\newline
[2] M.~Mikhasenko, B.~Ketzer and A.~Sarantsev, Phys. Rev. D \textbf{91}, 094015 (2015).\newline
[3] F.~K.~Guo \textit{et al.}, Rev. Mod. Phys. D \textbf{90}, 015004 (2018).\newline
[4] V.~Metag \textit{et al.}, EPJA 57 (2021) 325.\newline
\
Supported by DFG through SFB/TR16.
\end{document}
