S-waves and the Measurement of CP Violating Phases in Bs Decays

Abstract

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 -2beta_s, the "phase of Bs-\bar{B}s mixing," thought to be best measured in Bs -> J/psiϕdecays is of order -0.04, while the CP violating asymmetry in Bs -> ϕϕis predicted to be zero, due to the cancellation of the mixing phase with the decay phase. Recent measurements of β_s in J/psiϕ, while not definitive, are much larger than the Standard Model predictions. Measurements in the B^o and Ds+ systems of analogous modes point toward a 5-10% contamination of S-wave K+K- under the ϕpeak. 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/psi f0 useful for measuring β_s 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/psiϕmode. The error on β_s, however, may be similar. We also remark on S-wave problems with the Bs -> ϕϕmode, and possible systematic checks using Bs -> ϕf0.