Two narrow resonant states are observed in the Λb0 K− π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb^−1. The minimal quark content of the Λb0 K− π+ system indicates that these are excited Ξb0 baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m[Ξb(6327)0] = 6327.28{−0.21}{+0.23} ± 0.12 ± 0.24 and m[Ξb(6333)0] = 6332.69{−0.18}{+0.17} ± 0.03 ± 0.22 MeV, respectively, with a mass splitting of Δm = 5.41{−0.27}{+0.26} ± 0.12 MeV, where the uncertainties are statistical, systematic, and due to the Λb0 mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ[Ξb(6327)0] < 2.20 (2.56) and Γ[Ξb(6333)0] < 1.60 (1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξb0 resonances.
Observation of Two New Excited Ξb0 States Decaying to Λb0 K− π+
Calabrese, R.;Capriotti, L.;Couturier, B.;Fiorini, M.;Franzoso, E.;Giugliano, C.;Guarise, M.;Kotriakhova, S.;Luppi, E.;Neri, I.;Okamura, S.;Pappalardo, L. L.;Passalacqua, B.;Tomassetti, L.;
2022
Abstract
Two narrow resonant states are observed in the Λb0 K− π+ mass spectrum using a data sample of proton-proton collisions at a center-of-mass energy of 13 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 6 fb^−1. The minimal quark content of the Λb0 K− π+ system indicates that these are excited Ξb0 baryons. The masses of the Ξb(6327)0 and Ξb(6333)0 states are m[Ξb(6327)0] = 6327.28{−0.21}{+0.23} ± 0.12 ± 0.24 and m[Ξb(6333)0] = 6332.69{−0.18}{+0.17} ± 0.03 ± 0.22 MeV, respectively, with a mass splitting of Δm = 5.41{−0.27}{+0.26} ± 0.12 MeV, where the uncertainties are statistical, systematic, and due to the Λb0 mass measurement. The measured natural widths of these states are consistent with zero, with upper limits of Γ[Ξb(6327)0] < 2.20 (2.56) and Γ[Ξb(6333)0] < 1.60 (1.92) MeV at a 90% (95%) credibility level. The significance of the two-peak hypothesis is larger than nine (five) Gaussian standard deviations compared to the no-peak (one-peak) hypothesis. The masses, widths, and resonant structure of the new states are in good agreement with the expectations for a doublet of 1D Ξb0 resonances.File | Dimensione | Formato | |
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2022-AR-21-Obs_of_Two_New_Excited_Xib0_States_Decaying-PRL.pdf
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