Revisiting ΞQ - ΞQ' mixing in QCD sum rules

In this work, we perform a QCD sum rules analysis on Xi(Q) - Xi(Q)' mixing. Contributions from up to dimension 6 four-quark operators are considered. However, it turns out that only dimension-4 and dimension-5 operators contribute, which reveals the non-perturbative nature of mixing. In particular, we observe that only the diagrams with the two light quarks participating in gluon exchange contribute to the mixing. Our results indicate that the mixing angle theta(c) = (1.2 similar to 2.8)(degrees) for the Q = c case and theta(b) = (0.28 similar to 0.34)(degrees) for the Q = b case. Our prediction of theta c is consistent with the most recent Lattice QCD result within error. Such a small mixing angle seems unlikely to resolve the tension between the recent experimental measurement from Belle and Lattice QCD calculation for the semileptonic decay Xi(0 )(c)-> Xi(-)e(+)nu(e).

Automated summary

In this study, a QCD sum rules analysis is performed on the Xi(Q) - Xi(Q)' mixing. It is found that only dimension-4 and dimension-5 operators contribute to the mixing, indicating its non-perturbative nature. The mixing angle is predicted to be (1.2 to 2.8) degrees for the Q = c case and (0.28 to 0.34) degrees for the Q = b case. The small mixing angle is unlikely to resolve the tension between recent experimental measurement and lattice QCD calculation for the semileptonic decay Xi(0)(c) -> Xi(-)e(+)nu(e).