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 $90\mathrm{\%}$ confidence level upper limit is changing from $2.5\cdot {10}^{-6}$ to $2\cdot {10}^{-7}$ for the ALP mass from 0 to 200 MeV/$c^2$, except for the region of ${\pi }^0$ mass, where the upper limit is $4.4\cdot {10}^{-6}$.