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Observation of a new baryon state in the ∧0bπ+π- mass spectrum

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Original languageEnglish
Article number136
JournalJournal of High Energy Physics
Publication statusPublished - 23 Jun 2020


A new baryon state is observed in the $ {\Lambda}_{\mathrm{b}}^0{\pi}^{+}{\pi}^{-} $ mass spectrum with high significance using a data sample of pp collisions, collected with the LHCb detector at centre-of-mass energies $ \sqrt{s} $ = 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb$^{−1}$. The mass and natural width of the new state are measured to be$ {\displaystyle \begin{array}{l}m=6072.3\pm 2.9\pm 0.6\pm 0.2\ \mathrm{MeV},\\ {}\Gamma =72\pm 11\pm 2\ \mathrm{MeV},\end{array}} $where the first uncertainty is statistical and the second systematic. The third uncertainty for the mass is due to imprecise knowledge of the $ {\Lambda}_{\mathrm{b}}^0 $ baryon mass. The new state is consistent with the first radial excitation of the $ {\Lambda}_{\mathrm{b}}^0 $ baryon, the Λ$_{b}$(2S)$^{0}$ resonance. Updated measurements of the masses and the upper limits on the natural widths of the previously observed Λ$_{b}$(5912)$^{0}$ and Λ$_{b}$(5920)$^{0}$ states are also reported.[graphic not available: see fulltext]

ID: 155086798