Measurements of psi'-> pbar K+ sigma0 and chi_cj->pbar K+ Lambda

Using a sample of $1.06\times10^8$ $ψ^\prime$ mesons collected with the BESIII detector at the BEPCII $e^+e^-$ collider and $χ_{cJ}$ mesons produced via radiative transitions from the $ψ^\prime$, we report the first observation for $ψ^\prime\to \bar{p}K^+Σ^0 +c.c.$ (charge-conjugate), as well as improved measurements for the $χ_{cJ}$ hyperon decays $χ_{cJ}\to\bar{p}K^+Λ+c.c.$. The branching fractions are measured to be $\mathcal{B}(ψ^\prime\to \bar{p}K^+Σ^0+c.c)= (1.67\pm0.13\pm0.12)\times10^{-5}$, $\mathcal{B}(χ_{c0}\to\bar{p}K^+Λ+c.c.)= (13.2\pm0.3\pm1.0)\times10^{-4}$, $\mathcal{B}(χ_{c1}\to\bar{p}K^+Λ+c.c.)= (4.5\pm0.2\pm0.4)\times10^{-4}$ and $\mathcal{B}(χ_{c2}\to\bar{p}K^+Λ+c.c)= (8.4\pm0.3\pm0.6)\times10^{-4}$, where the first error is statistical, and the second is systematic. In the decay of $χ_{c0} \to \bar{p}K^+Λ+ c.c.$, an anomalous enhancement near threshold is observed in the invariant mass distribution of $\bar{p}Λ+c.c.$, which cannot be explained by phase space.

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