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تسجيل مستخدم جديدMeasurement of resonant and $CP$ components in $overline{B}_s^0rightarrow J/psi pi^+pi^-$ decays
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The resonant structure of the decay $overline{B}_s^0to J/psipi^+pi^-$ is studied using data corresponding to 3 fb$^{-1}$ of integrated luminosity from $pp$ collisions by the LHC and collected by the LHCb detector. Five interfering $pi^+pi^-$ states are required to describe the decay: $f_0(980),f_0(1500),f_0(1790),f_2(1270)$, and $f_2^{prime}(1525)$. An alternative model including these states and a non-resonant $J/psi pi^+pi^-$ component also provides a good description of the data. Based on the different transversity components measured for the spin-2 intermediate states, the final state is found to be compatible with being entirely $CP$-odd. The $CP$-even part is found to be $<2.3$% at 95% confidence level. The $f_0(500)$ state is not observed, allowing a limit to be set on the absolute value of the mixing angle with the $f_0(980)$ of $<7.7^{circ}$ at 90% confidence level, consistent with a tetraquark interpretation of the $f_0(980)$ substructure.
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The resonant structure of the reaction $overline{B}^0rightarrow J/psi pi^+pi^-$ 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 $qoverline{q}$ 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.
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