Observation of B$$^0$$ $$\rightarrow $$ $$\uppsi $$(2S)K$$^0_\mathrm {S}\uppi ^+\uppi ^-$$ and B$$^0_\mathrm {s}$$ $$\rightarrow $$ $$\uppsi $$(2S)K$$^0_\mathrm {S}$$ decays
European physical journal. C, Particles and fields