| Popis: |
We observe a narrow mass state decaying into Υ(1S)+γ, where the Υ(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551±0.014(stat.)±0.017(syst.) GeV/c2, which is consistent with that of the state recently observed by the ATLAS Collaboration. The data sample corresponds to an integrated luminosity of 1.3 fb−1 of pp collisions at s = 1.96 TeV accumulated with the D0 detector at the Fermilab Tevatron collider. |
