Searches for the light invisible axion-like particle in \(K^{+}\to\pi^{+}\pi^{0}a\) decay

A high statistics data sample of the \(K^{+}\) decays is recorded by the OKA collaboration. A missing mass analysis is performed to search for a light invisible pseudoscalar axion-like particle (ALP) \(a\) in the decay \(K^{+} \to \pi^{+} \pi^{0} a\). No signal is observed, the upper limits for the branching ratio of the decay are calculated. The \(90\%\) confidence level upper limit is changing from \(2.5\cdot10^{-6}\) to \(2\cdot10^{-7}\) for the ALP mass from 0 to 200 MeV/\(c^{2}\), except for the region of \(\pi^{0}\) mass, where the upper limit is \(4.4\cdot10^{-6}\).