Nonleptonic decays of Ξcc → Ξcπ with Ξc - Ec′ mixing

Aiming on testing the Xi(c) - Xi(c)'mixing, we study the decays of Xi(cc) -> Xi(c)pi with Xi(cc) = (Xi(++)(cc), Xi(+)(cc) ) Xi(c) = (Xi(()(c)'()), Xi(()(c)'()0)) and pi = (pi(+), pi(0)) . The soft-meson limit is considered along with the pole model, and the baryon matrix elements are evaluated by the bag model with and without removing the center-of-mass motion (CMM). We find that the four-quark operator matrix elements are about two times larger once the unwanted CMM is removed. We obtain that R = B (Xi(+)(cc) -> Xi(c)'(+) pi(+)) /B Xi(+)(cc) -> Xi(+)(c)pi(+) = 0.87(-0.11)(+0.17) and 1.45 with and without removing the CMM, where the former is close to the lower bound and the later is well consistent with R = 1/4 +/- 0.17 +/- 0.10 measured at LHCb. In addition, we show that after including the mixing the up-down asymmetry of alpha(Xi(+)(cc) -> Xi(()(c)'()),pi(+)) flips sign. Explicitly, we obtain that alpha(Xi(+)(cc) -> Xi(()(c)'()),pi(0)) 0.52 and alpha(Xi(+)(cc) -> Xi(0)(c),pi(+)) = 0.31 with and without the CMM corrections, respectively, which are all negative if the mixing is absence. As a bonus, a positive value of alpha(Xi(+)(cc) -> Xi(c)'(0),pi(+)) in experiments can also serve as the evidence of the W-exchange contributions.

Automated summary

Aiming to test the Xi(c) - Xi(c)' mixing, we investigate the decays of Xi(cc) -> Xi(c)pi. By considering the soft-meson limit and pole model, we evaluate the baryon matrix elements using the bag model with and without removing the center-of-mass motion (CMM). The removal of unwanted CMM leads to a doubling of the four-quark operator matrix elements. After including the mixing effects, the up-down asymmetry of alpha(Xi(+)(cc) -> Xi(()(c)'()),pi(+)) flips sign, providing evidence for W-exchange contributions.