Interpretation of CP violation measurements using charmonium decays, in both the B ̄0 and B̄s0 systems, can be subject to changes due to "penguin" type diagrams. These effects can be investigated using measurements of the Cabibbo-suppressed B ̄0→J/ ψπ +π - decays. The final state composition of this channel is investigated using a 1.0 fb -1 sample of data produced in 7 TeV pp collisions at the LHC and collected by the LHCb experiment. A modified Dalitz-plot analysis is performed using both the invariant mass spectra and the decay angular distributions. An improved measurement of the B ̄0→J/ψπ +π - branching fraction of (3.97±0.09±0.11±0.16)×10 -5 is reported where the first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty of the branching fraction of the decay B -→J/ψK - used as a normalization channel. Significant production of f 0(500) and ρ(770) resonances is found in the substructure of the J/ψπ +π - final state, and this indicates that they are viable final states for CP violation studies. In contrast evidence for the f 0(980) resonance is not found. This allows us to establish the first upper limit on the branching fraction product B(B ̄0→J/ψf 0(980))×B(f 0(980)→π +π -)<1.1×10 -6, leading to an upper limit on the absolute value of the mixing angle of the f 0(980) with the f 0(500) of less than 31, both at 90% confidence level.
|Journal||Physical Review D - Particles, Fields, Gravitation and Cosmology|
|Publication status||Published - 1 Mar 2013|
Copyright 2013 Elsevier B.V., All rights reserved.
All Science Journal Classification (ASJC) codes
- Nuclear and High Energy Physics
- Physics and Astronomy (miscellaneous)