The resonant structure of the reaction B⎯⎯⎯0→J/ψπ+π− 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 π+π− pair and three decay angular distributions are used to determine the fractions of the resonant and non-resonant components. Six interfering π+π− states: ρ(770), f0(500), f2(1270), ρ(1450), ω(782) and ρ(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 f0(980) meson is not seen and the upper limit on its presence, compared with the observed f0(500) rate, is inconsistent with a model of tetraquark substructure for these scalar mesons at the eight standard deviation level. In the qq⎯⎯ model, the absolute value of the mixing angle between the f0(980) and the f0(500) scalar mesons is limited to be less than 17∘ at 90% confidence level.
Measurement of the resonant and CP components in B¯0→J/ψπ+π− decays
ANDREOTTI, Mirco;BALDINI, Wander;BOZZI, Concezio;CALABRESE, Roberto;CORVO, Marco;FIORE, Marco;FIORINI, Massimiliano;LUPPI, Eleonora;MANZALI, Matteo;SAVRIE', Mauro;TELLARINI, Giulia;TOMASSETTI, Luca;
2014
Abstract
The resonant structure of the reaction B⎯⎯⎯0→J/ψπ+π− 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 π+π− pair and three decay angular distributions are used to determine the fractions of the resonant and non-resonant components. Six interfering π+π− states: ρ(770), f0(500), f2(1270), ρ(1450), ω(782) and ρ(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 f0(980) meson is not seen and the upper limit on its presence, compared with the observed f0(500) rate, is inconsistent with a model of tetraquark substructure for these scalar mesons at the eight standard deviation level. In the qq⎯⎯ model, the absolute value of the mixing angle between the f0(980) and the f0(500) scalar mesons is limited to be less than 17∘ at 90% confidence level.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.