Investigating the color-suppressed decays Λb → Λψ Aye in the perturbative QCD approach

The nonleptonic two-body Lambda(b) -> Lambda(psi) decays with psi = J/psi, or psi(2S) are investigated based on the perturbative QCD approach. These are color-suppressed processes in which the nonfactorizable contributions are confirmed to be dominant. Angular momentum conservation allows us to describe the concerned decays by four independent complex helicity amplitudes. It is observed that the negativehelicity states for the A baryon are preferred as expected in the left-handed nature of the charged-current interaction. The obtained results for the helicity amplitudes are used to compute the branching ratios and various observable parameters, which are then compared to the existing theoretical predictions and experimental data. In particular, we predict the ratio R = B(Lambda(b)->Lambda(psi)(2S))/B(Lambda(b)->Lambda J/psi) = 0.47(-0.00)(+0.02) in comparison with 0508 +/- 0.023 from the Particle Data Group at the level of 1 standard deviation. We also briefly explore the long-distance contributions to the semileptonic Lambda(b) -> Al(+)l(-) decays in the kinematic regions where the dilepton invariant masses are around the J/psi and psi(2S) resonances.

Automated summary

The nonleptonic two-body Lambda(b) -> Lambda(psi) decays, with psi = J/psi or psi(2S), are investigated using the perturbative QCD approach. The dominance of nonfactorizable contributions is confirmed in these color-suppressed processes. By considering four independent complex helicity amplitudes, the concerned decays can be accurately described due to angular momentum conservation. The obtained helicity amplitudes are then utilized to calculate branching ratios and observable parameters, and compared with existing theoretical predictions and experimental data. Additionally, the long-distance contributions to semileptonic Lambda(b) -> Al(+)l(-) decays in the vicinity of J/psi and psi(2S) resonances are briefly explored.