We report the observation of a new structure in the Λ_b^0π^+π^- spectrum using the full LHCb data set of pp collisions, corresponding to an integrated luminosity of 9 fb^-1, collected at sqrt[s]=7, 8, and 13 TeV. A study of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The masses and widths of these states are measured to be m_Λ_b(6146)^0=6146.17±0.33±0.22±0.16 MeV,m_Λ_b(6152)^0=6152.51±0.26±0.22±0.16 MeV,Γ_Λ_b(6146)^0=2.9±1.3±0.3 MeV,Γ_Λ_b(6152)^0=2.1±0.8±0.3 MeV,with a mass splitting of Δm=6.34±0.32±0.02 MeV, where the first uncertainty is statistical, the second systematic. The third uncertainty for the mass measurements derives from the knowledge of the mass of the Λ_b^0 baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of Λ_b(1D)^0 states.
Observation of New Resonances in the Λ_b^0π^+π^- System
Veltri, M;
2019
Abstract
We report the observation of a new structure in the Λ_b^0π^+π^- spectrum using the full LHCb data set of pp collisions, corresponding to an integrated luminosity of 9 fb^-1, collected at sqrt[s]=7, 8, and 13 TeV. A study of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The masses and widths of these states are measured to be m_Λ_b(6146)^0=6146.17±0.33±0.22±0.16 MeV,m_Λ_b(6152)^0=6152.51±0.26±0.22±0.16 MeV,Γ_Λ_b(6146)^0=2.9±1.3±0.3 MeV,Γ_Λ_b(6152)^0=2.1±0.8±0.3 MeV,with a mass splitting of Δm=6.34±0.32±0.02 MeV, where the first uncertainty is statistical, the second systematic. The third uncertainty for the mass measurements derives from the knowledge of the mass of the Λ_b^0 baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of Λ_b(1D)^0 states.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
