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

Peter Clarke, Robert Currie, Stephan Eisenhardt, Silvia Gambetta, Franz Muheim, Matthew Needham, Marco Pappagallo, Mark Williams, LHCb Collaboration

Research output: Contribution to journalArticlepeer-review

## Abstract

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]
Original language English 136 Journal of High Energy Physics 2020 https://doi.org/10.1007/JHEP06(2020)136 Published - 23 Jun 2020

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