Measurement of the resonant and CP components in B¯0→J/ψπ+π− decays

Le résumé fourni par la source

The resonant structure of the reaction ${\overline{B}}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ is studied using data from $3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity collected by the LHCb experiment, one third at 7 TeV center-of-mass energy and the remainder at 8 TeV. The invariant mass of the ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ pair and three decay angular distributions are used to determine the fractions of the resonant and nonresonant components. Six interfering ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ states, $\ensuremath{\rho}(770)$, ${f}_{0}(500)$, ${f}_{2}(1270)$, $\ensuremath{\rho}(1450)$, $\ensuremath{\omega}(782)$ and $\ensuremath{\rho}(1700)$, are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative charge parity fractions of each of the resonant final states are determined. The ${f}_{0}(980)$ meson is not seen and the upper limit on its presence, compared with the observed ${f}_{0}(500)$ rate, is inconsistent with a model where these scalar mesons are formed from two quarks and two antiquarks (tetraquarks) at the eight standard deviation level. In the $q\overline{q}$ model, the absolute value of the mixing angle between the ${f}_{0}(980)$ and the ${f}_{0}(500)$ scalar mesons is limited to be less than 17\ifmmode^\circ\else\textdegree\fi{} at 90% confidence level.

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