Search for the manifestation of the mesic-nuclei on the $dd \rightarrow ^{3}HeN \pi$ excitation function measured with WASA-at-COSY

We search for an evidence of $\eta$-mesic $^{4}He$ with the WASA-at-COSY detector. Two dedicated experiments were performed at the Cooler Synchrotron COSY-Jülich. The experimental method is based on the measurement of the excitation functions for the two reaction channels: $dd \rightarrow ^{3}Hep\pi^{-}$ and $dd \rightarrow ^{3}Hen\pi^{0}$, where the outgoing N–π pairs originate from the conversion of the $\eta$ meson on a nucleon inside the He nucleus. In this contribution, the experimental method is shortly described and preliminary excitation functions from the 2010 data are presented