New bound on the vectorial axion-down-strange coupling from $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ data

Diego Guadagnoli, Axel Iohner, Cristina Lazzeroni +3

We reinterpret publicly available $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ data collected by NA62 from 2016 to 2024 to constrain the fundamental vectorial coupling of the QCD axion to down and strange…