S-waves and the measurement of CP violating phases in Bs decays

Heavy, as yet undiscovered particles, can affect measurements of CP violation in the B system. Measuring CP violation in the Bs system provides an excellent place to observe such effects since standard model sources are predicted to produce very small effects. The angle -2βs, the "phase of Bs-B̄s mixing," thought to be best measured in Bs→J/ψ decays is of order -0.04, while the CP violating asymmetry in Bs→ is predicted to be zero, due to the cancellation of the mixing phase with the decay phase. Recent measurements of βs in J/ψ, while not definitive, are much larger than the standard model predictions. Measurements in the B0 and Ds+ systems of analogous modes point toward a 5-10% contamination of S-wave K+K- under the peak. This S-wave was not taken into account in these recent analyses. Furthermore this S-wave can also materialize as a f0(980) meson that decays to π+π-, making the final state J/ψf0 useful for measuring βs with the added advantage of not requiring an angular analysis. Rate estimates, while not precise, predict four to five times fewer such events than those in the J/ψ mode. The error on βs, however, may be similar. We also remark on S-wave problems with the Bs→ mode, and possible systematic checks using Bs→f0.