Study of heavy quark conserving weak decays in the quark model

Abstract

Within the framework of a constituent quark model, we investigate the heavy quark conserving weak decays of Ξc and Ξb. This process involves elementary transitions of us→du or s→udu¯ with the heavy quark as a spectator, while for the charmed baryon in the initial state it can also occur via cs→dc to conserve the heavy quark flavor in the weak decays. It shows that the heavy quark symmetry (HQS) plays an essential role in the processes where the heavy quark acts as a spectator. For the Ξc decays, the dominance of the pole terms in the parity-conserving transitions is evident. This can naturally explain the sizable branching ratio for Ξc0→Λcπ− as recently reported by LHCb. The same mechanism predicts a large branching ratio for Ξc+→Λcπ0. In contrast, the decays of Ξb will only go through the parity-violating processes because of the HQS. In addition, the branching ratios of the Ξc+→Λcπ0 and Ξb0→Λbπ0 processes are also predicted for the further experimental measurement.