Spin-1/2 invisible particles in heavy meson decays.

The flavor-changing neutral current decay processes of the B and Bc mesons with the final states involving spin-1/2 particles are investigated. By considering the background of the Standard Model, where ν̄ν contributes the missing energy and the experimental upper bounds for the branching fractions, we get the constraints of the coupling constants of the quark-antiquark and the assumed invisible particles χ̄χ. The constraints of the coupling constants are then used to study the similar processes of the Bc meson. At some specific region of mχ, the upper limit of BR(Bc→D(s)χ̄χ) is of the order of 10-6, while for BR(Bc→D∗(s)χ̄χ)), it is 10-5. The possibility of distinguishing χ to be a Majorana or Dirac fermion by the differential branching fractions is also discussed. [ABSTRACT FROM AUTHOR]