Rare decays of mesons for new physics

[shakeel]

Why the semi-leptonic decays of mesons involving neutrinos are consider as clean signal for new Physics. As for as I think these are free from hadronic complexities (because we do not know exactly about strong interactions) and electromagnetic interference (because neutrinos do not couple to photons ). Can anyone guide me or correct me in this regard.
Thanks

 

[mfb]

Decays which can occur via the strong interaction are dominated by SM physics (the strong interaction), you don't see small contributions from new physics (if present).
You need some weaker processes - rare decays. Semileptonic decays are one possibility there, the decays to two muons are even better, and some hadronic decays are interesting, too.
In addition, weak processes are often easier to calculate.