Spin effects in Bc → Xc¯cπ(ρ) decays.

Spin effects in B c → X c¯ c π(ρ) decays. Abstract The two-particle hadronic decays of B c meson into S-wave and P-wave charmonium states X c¯ c are considered in the framework of hard gluon exchange model. It is shown that decay width of B c meson into S-wave charmonium states doubly exceeds one for P-wave states. In compare with the previous estimations we predict the enhancement by 8 % the branching ratio for the B c decays into J/ψ in the two-particle hadronic decays via the contribution of the radiative decays of P-wave states in the cascade processes. The first observation of B c meson at FNAL [1] motivates new theoretical study in the field of heavy quarkonium physics. The unique properties of B c meson, containing heavy quarks of different flavours, may be studied, first of all, via decay modes with J/ψ meson in the final state. We consider here two-particle hadronic decays of B c meson into S-wave and P-wave charmonium states B c → X c¯ c + π(ρ), (1) where X c¯ c = η c or J/ψ for S-wave states, and X c¯ c = h c , χ c0 , χ c1 , χ c2 for P-wave states. These decays are of considerable interest as a clean signal of B c meson production in high energy collisions [2]. Because of the large momentum transfer to the spectator quark (|k 2 | ∼ m 2 c ≫ Λ QCD) in the decays (1.1), the hard scattering formalism is more appropriate than the spectator model, which based on the transition form-factor calculation under the overlapping of the quarkonium wave functions. In contrast to the spectator model, the hard scattering formalism results in the approximate double enhancement of the decay amplitude for the decays B c → J/ψ(η c)π, as it was found in [3, 4].