By analysing $e^+e^-$ annihilation data corresponding to an integrated luminosity of 368.48~pb$^{ -1}$ collected at the centre-of-mass energies of $\sqrt{ s} = 4.918$ and $4.951$~GeV with the BESIII detector, we report the first observation of $\Lambda_{ c}(2595)^{ +}$ and $\Lambda_{ c}(2625)^{ +}\to \Lambda^{ +}_{ c}\pi^0\pi^0$ with statistical significances of 7.9$\sigma$ and 11.8$\sigma$, respectively. The branching fractions of $\Lambda_{ c}(2595)^{ +}$ and $\Lambda_{ c}(2625)^{ +}\to \Lambda^{ +}_{ c}\pi^0\pi^0$ are measured to be $(59.5 \pm 11.1_{ \rm stat.} \pm 7.9_{ \rm syst.}) \%$ and $(41.0 \pm 5.2_{ \rm stat.} \pm 3.3_{ \rm syst.}) \%$, respectively. The absolute branching fraction of $\Lambda_{ c}(2595)^{ +}$ is consistent with the expectation of the mechanism referred to as the threshold effect, proposed for the strong decays of $\Lambda_{ c}(2595)^{ +}$ within uncertainty.
Categories: hep-ex