I will review the interesting decays KL->pi0 ll, K+->pi+ l l and KS->mu mu, complementary to the golden K+->pi+ nu nubar and KL->pi0 nu nubar. I will review the theoretical challenges and phenomenological interest. As possible strategy to evaluate hadronic matrix elements we discuss large N, N large number of colours. Also I will highlight possible new directions to uncover new physics
For the first time in history, the ultra-rare KL->pi0nunubar decay, also known as the “Golden Mode”, can be experimentally probed at the level of its Standard Model predicted branching ratio of 3x10^{-11}. This milestone is being pursued through a two-stage approach by the KOTO experiment and its successor KOTO II at J-PARC. The current KOTO experiment has entered a phase of stable data...
The $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ decay is a golden mode for flavour physics. Its branching ratio is predicted with high precision by the Standard Model to be less than $10^{-10}$, and this decay mode is highly sensitive to indirect effects of new physics up to the highest mass scales. A new measurement of the $K^{+}\rightarrow\pi^{+}\nu\bar{\nu}$ decay by the NA62 experiment at the...
