The study of light invisible particles in B _c decays

In this paper, we study the light scalar and pseudoscalar invisible particles in the flavor changing neutral current processes of the B _c meson. Effective operators are introduced to describe the couplings between quarks and light invisible particles. The Wilson coefficients are extracted from the experimental results of the B and D mesons, which are used to predict the upper limits of the branching fractions of the similar decay processes for the B _c meson. The hadronic transition matrix element is calculated with the instantaneously approximated Bethe-Salpeter method. The upper limits of the branching fractions when m _χ taking different values are presented. It is found that at some region of m _χ , the channel B _c → D _s ^(*) χχ has the largest upper limit which is of the order of 10 ⁻⁶ , and for B _c → D _s ^* χχ ^† , the largest value of the upper limits can achieve the order of 10 ⁻⁵ . Other decay modes, such as B _c → D ^(*) χχ ^(†) and B _c → B ^(*) χχ ^(†) , are also considered.