Observation of $B^{+}\to p\bar{\mathrm{\Lambda }}{K}^{+}{K}^{-}$ and $B^{+}\to \bar{p}\mathrm{\Lambda }{K}^{+}{K}^{+}$

We report the study of \OK \ and \SK \ using a $772\times {10}^6$ $B\bar{B}$ pair data sample recorded on the $\mathrm{{\rm Y}}(4\mathrm{S})$ resonance with the Belle detector at KEKB. The following branching fractions are measured: $\mathcal{B}$(\OKPHSP) $=$ $(4.22_{-0.44}^{+0.45}\pm 0.51)\times {10}^{-6}$, $\mathcal{B}$(\SKPHSP) $=$ $(3.81_{-0.37}^{+0.39}\pm 0.45)\times {10}^{-6}$, $\mathcal{B}$(\ETACD+c.c.) $=$ $(2.91_{-0.35}^{+0.37}\pm 0.36)\times {10}^{-3}$ and $\mathcal{B}$(\PLPHI) $=$ $(8.18\pm 2.15\pm 0.79)\times {10}^{-7}$, where c.c. denotes the corresponding charge-conjugation process. The intermediate resonance decays are excluded in the four-body decay measurements. We also found evidences for $\mathcal{B}$(\ETACS+c.c.) $=$ $(3.59 \pm 1.52 \pm 0.47) \times 10^{-3}$and$$\mathcal{B}$$(\text{LLKO})$=$ $(2.30 \pm 0.65 \pm 0.25) \times 10^{-6}$. No significant signals are found for \JPSIS+c.c. and \LLKS \ ; we set the 90% confidence level upper limits on their decay branching fractions as $< 1.85\times10^{-3}$and$< 2.14\times10^{-6}$, respectively.