Search for ${\mathrm{\Lambda }}_c^{+}\to \varphi p{\pi }^0$ and branching fraction measurement of ${\mathrm{\Lambda }}_c^{+}\to K^{-}{\pi }^{+}p{\pi }^0$

We have searched for the Cabibbo-suppressed decay ${\mathrm{\Lambda }}_c^{+}\to \varphi p{\pi }^0$ in $e^{+}{e}^{-}$ collisions using a data sample corresponding to an integrated luminosity of 915 $\mathrm{f}{\mathrm{b}}^{-1}$. The data were collected by the Belle experiment at the KEKB $e^{+}{e}^{-}$ asymmetric-energy collider running at or near the $\mathrm{{\rm Y}}(4S)$ and $\mathrm{{\rm Y}}(5S)$ resonances. No significant signal is observed, and we set an upper limit on the branching fraction of $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to \varphi p{\pi }^0)<15.3\times {10}^{-5}$ at 90% confidence level. The contribution for nonresonant ${\mathrm{\Lambda }}_c^{+}\to K^{+}{K}^{-}p{\pi }^0$ decays is found to be consistent with zero and the corresponding upper limit on its branching fraction is set to be $$\mathcal{B}$(\Lambda_c^+\to K^+K^-p\pi^0){\rm NR} <6.3\times10^{-5} $ at 90% confidence level. We also measure the branching fraction for the Cabibbo-favored decay ${\mathrm{\Lambda }}_c^{+}\to K^{-}{\pi }^{+}p{\pi }^0$; the result is $$\mathcal{B}$(\Lambda_c^+\to K^-\pi^+p\pi^0)= (4.42\pm0.05, (\rm stat.) \pm 0.12, (\rm syst.) \pm 0.16, ($\mathcal{B}${\rm Norm}))%$, which is the most precise measurement to date. Finally, we have searched for an intermediate hidden-strangeness pentaquark decay $P_s^{+}\to \varphi p$. We see no evidence for this intermediate decay and set an upper limit on the product branching fraction of ${\cal B}(\Lambda_c^+\to P^+_s \pi^0)\times {\cal B}(P^+_s\to\phi p) <8.3\times 10^{-5}$ at 90% confidence level.