Evidence for the decays of ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}\eta$ and ${\mathrm{\Sigma }}^{+}{\eta }^{\mathrm{\prime }}$

We study the hadronic decays of ${\mathrm{\Lambda }}_c^{+}$ to the final states ${\mathrm{\Sigma }}^{+}\eta$ and ${\mathrm{\Sigma }}^{+}{\eta }^{\mathrm{\prime }}$, using an $e^{+}{e}^{-}$ annihilation data sample of 567 pb${}^{-1}$ taken at a center-of-mass energy of 4.6 GeV with the BESIII detector at the BEPCII collider. We find evidence for the decays ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}\eta$ and ${\mathrm{\Sigma }}^{+}{\eta }^{\mathrm{\prime }}$ with statistical significance of $2.5\sigma$ and $3.2\sigma$, respectively. Normalizing to the reference decays ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^0$ and ${\mathrm{\Sigma }}^{+}\omega$, we obtain the ratios of the branching fractions $\frac{{\mathcal B}(\Lambda_c^+\to\Sigma^+\eta)}{{\mathcal B}(\Lambda_c^+\to\Sigma^+\pi^0)}$and$\frac{{\mathcal B}(\Lambda_c^+\to\Sigma^+\eta^\prime)}{{\mathcal B}(\Lambda_c^+\to\Sigma^+\omega)}$tobe$0.35 \pm 0.16 \pm 0.03$and$0.86 \pm 0.34 \pm 0.07$, respectively. The upper limits at the 90% confidence level are set to be $\frac{{\mathcal B}(\Lambda_c^+\to\Sigma^+\eta)}{{\mathcal B}(\Lambda_c^+\to\Sigma^+\pi^0)}<0.58$and$\frac{{\mathcal B}(\Lambda_c^+\to\Sigma^+\eta^\prime)}{{\mathcal B}(\Lambda_c^+\to\Sigma^+\omega)}<1.2$. Using BESIII measurements of the branching fractions of the reference decays, we determine $\mathcal B({\Lambda_{c}^{+}\rightarrow\Sigma^{+}\eta})=(0.41\pm0.19\pm0.05)%$($<0.68%$)and$\mathcal B({\Lambda_{c}^{+}\rightarrow\Sigma^{+}\eta’})=(1.34\pm0.53\pm0.21)%$($<1.9%$). Here, the first uncertainties are statistical and the second systematic. The obtained branching fraction of ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}\eta$ is consistent with the previous measurement, and the branching fraction of ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\eta }^{\mathrm{\prime }}$ is measured for the first time.