Search for the familon via B± → π±X0, B± → K±X0, and B0 → Ks 0X0 decays

We have searched for the two-body decay of the B meson to a light pseudoscalar meson h = π γ , K γ , K 0 S and a massless neutral feebly interacting particle X° such as the familon, the Nambu-Goldstone boson associated witha spontaneously broken global family symmetry. We find no significant signal by analyzing a data sample containing 9.7 X 10 6 BB mesons collected with the CLEO detector at the Cornell Electron Storage Ring, and set 90% C.L. upper limits B(B γ → h γ X 0 ) = 4.9 X 10 - 5 and B(B 0 → K 0 S X 0 ) = 5.3 × 10 - 5 . These limits correspond to a lower bound of approximately 10 8 GeV on the family symmetry breaking scale with vector coupling involving the third generation of quarks.