Observation of New Resonances in the Λb0π+π− System

Résumé fourni par la source

We report the observation of a new structure in the ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ spectrum using the full LHCb data set of $pp$ collisions, corresponding to an integrated luminosity of $9\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, 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 ${m}_{{\mathrm{\ensuremath{\Lambda}}}_{b}{(6146)}^{0}}=6146.17\ifmmode\pm\else\textpm\fi{}0.33\ifmmode\pm\else\textpm\fi{}0.22\ifmmode\pm\else\textpm\fi{}0.16\text{ }\text{ }\mathrm{MeV},\phantom{\rule{0ex}{0ex}}{m}_{{\mathrm{\ensuremath{\Lambda}}}_{b}{(6152)}^{0}}=6152.51\ifmmode\pm\else\textpm\fi{}0.26\ifmmode\pm\else\textpm\fi{}0.22\ifmmode\pm\else\textpm\fi{}0.16\text{ }\text{ }\mathrm{MeV},{\mathrm{\ensuremath{\Gamma}}}_{{\mathrm{\ensuremath{\Lambda}}}_{b}{(6146)}^{0}}=2.9\ifmmode\pm\else\textpm\fi{}1.3\ifmmode\pm\else\textpm\fi{}0.3\text{ }\text{ }\mathrm{MeV},{\mathrm{\ensuremath{\Gamma}}}_{{\mathrm{\ensuremath{\Lambda}}}_{b}{(6152)}^{0}}=2.1\ifmmode\pm\else\textpm\fi{}\phantom{\rule{0ex}{0ex}}0.8\ifmmode\pm\else\textpm\fi{}0.3\text{ }\text{ }\mathrm{MeV},$with a mass splitting of $\mathrm{\ensuremath{\Delta}}m=6.34\ifmmode\pm\else\textpm\fi{}0.32\ifmmode\pm\else\textpm\fi{}0.02\text{ }\text{ }\mathrm{MeV}$, 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 ${\mathrm{\ensuremath{\Lambda}}}_{b}^{0}$ baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of ${\mathrm{\ensuremath{\Lambda}}}_{b}{(1D)}^{0}$ states.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.