Study of excited ${\mathrm{\Lambda }}_{\mathrm{b}}^0$ states decaying to ${\mathrm{\Lambda }}_{\mathrm{b}}^0{\pi }^{+}{\pi }^{-}$ in proton-proton collisions at $\sqrt{s}=$ 13 TeV

A study of excited ${\mathrm{\Lambda }}_{\mathrm{b}}^0$ baryons is reported, based on a data sample collected in 2016-2018 with the CMS detector at the LHC in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of up to 140 fb${}^{-1}$. The existence of four excited ${\mathrm{\Lambda }}_{\mathrm{b}}^0$ states: ${\mathrm{\Lambda }}_{\mathrm{b}}$(5912)${}^0$, ${\mathrm{\Lambda }}_{\mathrm{b}}$(5920)${}^0$, ${\mathrm{\Lambda }}_{\mathrm{b}}$(6146)${}^0$, and ${\mathrm{\Lambda }}_{\mathrm{b}}$(6152)${}^0$ in the ${\mathrm{\Lambda }}_{\mathrm{b}}^0{\pi }^{+}{\pi }^{-}$ mass spectrum is confirmed, and their masses are measured. The ${\mathrm{\Lambda }}_{\mathrm{b}}^0{\pi }^{+}{\pi }^{-}$ mass distribution exhibits a broad excess of events in the region of 6040-6100 MeV, whose origin cannot be discerned with the present data.