Optimal observable analysis for the decay $b \to s$ plus missing energy

Abstract: The decay $b\to s\nu\bar\nu$ has been a neglected sibling of $b\to s\ell<sup>+\ell<sup>-$ because neutrinos pass undetected and hence the process offers less number of observables. We show how the decay $b\to s~+$~invisible(s) can shed light, even with a limited number of observables, on possible new physics beyond the Standard Model and also show, quantitatively, the reach of future $B$ factories like SuperBelle to uncover such new physics. Depending on the operator structure of new physics, different channels may act as the best possible probe. We show, using the Optimal Observable technique, how almost the entire parameter space allowed till now can successfully be probed at a high luminosity $B$ factory.