$K\to \pi \nu \bar{\nu }$ spectra and NA62 interpretation

Using the measured and projected invisible mass spectrum of the $K^{+}\to {\pi }^{+}\nu \bar{\nu }$ mode, we determine the current and future constraints within the model-independent framework of the weak effective theory at dimension-six. We work in two different operator bases depending whether neutrinos are Majorana or Dirac fermions. This makes it possible to transparently incorporate mass effects of additional sterile neutrinos for all operators.