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• Autores: Alconada Verzini, María Josefina; Alonso, Francisco; Arduh, Francisco Anuar; Dova, María Teresa; Monticelli, Fernando Gabriel; Wahlberg, Hernán Pablo; The ATLAS Collaboration
• Año de publicación: 2015
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Física; branching ratio; ATLAS detector; proton–proton collisions
• Institución: Universidad Nacional de La Plata

An observation of the ${\mathrm{\Lambda }}_b^0\to \psi (2S){\mathrm{\Lambda }}^0$ decay and a comparison of its branching fraction with that of the ${\mathrm{\Lambda }}_b^0\to J/\psi {\mathrm{\Lambda }}^0$ decay has been made with the ATLAS detector in proton–proton collisions at $\sqrt{s}=8\text{TeV}$ at the LHC using an integrated luminosity of 20.6 fb−1. The $J/\psi$ and $\psi (2S)$ mesons are reconstructed in their decays to a muon pair, while the ${\mathrm{\Lambda }}^0\to p{\pi }^{-}$ decay is exploited for the ${\mathrm{\Lambda }}^0$ baryon reconstruction. The ${\mathrm{\Lambda }}_b^0$ baryons are reconstructed with transverse momentum $p_{\mathrm{T}}>10\text{GeV}$ and pseudorapidity $|\eta |<2.1$. The measured branching ratio of the ${\mathrm{\Lambda }}_b^0\to \psi (2S){\mathrm{\Lambda }}^0$ and ${\mathrm{\Lambda }}_b^0\to J/\psi {\mathrm{\Lambda }}^0$ decays is $\mathrm{\Gamma }({\mathrm{\Lambda }}_b^0\to \psi (2S){\mathrm{\Lambda }}^0)/\mathrm{\Gamma }({\mathrm{\Lambda }}_b^0\to J/\psi {\mathrm{\Lambda }}^0)=0.501\pm 0.033(\mathrm{stat})\pm 0.019(\mathrm{syst})$, lower than the expectation from the covariant quark model.
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