  The framed standard model (FSM), constructed to explain, with some success,
why there should be 3 and apparently only 3 generations of quarks and leptons
in nature falling into a hierarchical mass and mixing pattern, suggests also,
among other things, a scalar boson U, with mass around 17 MeV and small
couplings to quarks and leptons, which might explain the g-2 anomaly reported
in experiment. The U arises in FSM initially as a state in the predicted
`hidden sector' with mass around 17 MeV, which mixes with the standard model
(SM) Higgs $h_W$, acquiring thereby a coupling to quarks and leptons and a mass
just below 17 MeV. The initial purpose of the present paper is to check whether
this proposal is compatible with experiment on semileptonic decays of Ks and Bs
where the U can also appear. The answer to this we find is affirmative, in that
the contribution of U to new physics as calculated in the FSM remains within
the experimental bounds, but only if $m_U$ lies within a narrow range just
below the unmixed mass. As a result from this, one has an estimate $m_U \sim 15
- 17$ MeV for the mass of $U$, and from some further considerations the
estimate $\Gamma_U \sim 0.02$ eV for its width, both of which may be useful for
an eventual search for it in experiment. And, if found, it will be, for the
FSM, not just the discovery of a predicted new particle, but the opening of a
window into a whole ``hidden sector" containing at least some, perhaps ven the
bulk, of the dark matter in the universe.
