Measurement of the CP-violating phase β in B0→J/ψπ+π- decays and limits on penguin effects

Abstract

Time-dependent CP violation is measured in the ( ) B 0 → J /ψπ +π − channel for each π +π − resonant final state using data collected with an integrated luminosity of 3.0 fb−1 in pp collisions using the LHCb detector. The final state with the largest rate, J /ψρ0(770), is used to measure the CP-violating angle 2βeff to be (41.7 ± 9.6+2.8 −6.3)◦. This result can be used to limit the size of penguin amplitude contributions to CP violation measurements in, for example, ( ) B 0 s → J /ψφ decays. Assuming approximate SU(3) flavour symmetry and neglecting higher order diagrams, the shift in the CP-violating phase φs is limited to be within the interval [−1.05◦, +1.18◦] at 95% confidence level. Changes to the limit due to SU(3) symmetry breaking effects are also discussed