Abstract
The resonant structure of the reaction $\overline{B}^0\rightarrow J/\psi \pi^+\pi^-$ is studied using data from 3 fb$^{-1}$ 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 $\pi^+\pi^-$ pair and three decay angular distributions are used to determine the fractions of the resonant and non-resonant components. Six interfering $\pi^+\pi^-$ states: $\rho(770)$, $f_0(500)$, $f_2(1270)$, $\rho(1450)$, $\omega(782)$ and $\rho(1700)$ are required to give a good description of invariant mass spectra and decay angular distributions. The positive and negative CP 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 of tetraquark substructure for these scalar mesons 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 $17^{\circ}$ at 90% confidence level.
Highlights
The decay mode B 0 → J=ψπþπ− is of particular interest in the study of charge parity (CP) violation in the B system
The effects of penguin topologies can be investigated by using the J=ψπþπ− decay and comparing different measurements of the CP violating phase, β, individual channels such as B 0 → J=ψρ0
We measure the resonant substructure and CP content of the B 0 → J=ψπþπ− decay from data corresponding to 3 fb−1 of integrated luminosity collected with the LHCb detector [6] using pp collisions
Summary
[2], if these scalar states are tetraquarks, the ratio of decay widths is predicted to be 1=2. The B 0 → J=ψπþπ− decay was first observed by the BABAR Collaboration [3] It has been previously studied by LHCb using data from 1 fb−1 of integrated luminosity [4]. A new theoretical approach [5] allows us to include all the angular information and measure the fraction of CP even and CP odd states. This information is vital to any subsequent CP violation measurements
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