[ ACP(B±→K±π+π–) = +0.034 ± 0.009 ± 0.004 ± 0.007 ]
[ ACP(B±→K±K+K–) = -0.046 ± 0.009 ± 0.005 ± 0.007 ]
LHCb physicists have presented today at the ICHEP2012 Conference in Melbourne measurements of differences between properties of matter and antimatter (CP violation asymmetry) in the charmless three-body B meson decays B±→K±π+π– and B±→K±K+K–. The dominant B meson decays involve a beauty b-quark decay into a charm c-quark. In the rarer charmless decays (without charmed mesons) discussed here the b-quark decays into a u,d or s-quark. LHCb physicists have measured the charge asymmetry ACP obtained from the difference between negative and positive B event rates. The numerical values of measured asymmetries are shown above. The significance is 2.8σ for the B±→K±π+π– decay and 3.7σ for the B±→K±K+K– channel. The latter is the first evidence of inclusive CP asymmetry in charmless three-body B± decays.
click the image for higher resolution
The results presented here are obtained by integrating (summing) the asymmetries over all kinematical variables of particles observed in the decays of B mesons. It is interesting to note that much larger asymmetries are observed in some small special regions, like invariant mass squared of the π+π– pair in the K±π+π– decay lower than 1 GeV2, or of the K+K– pair in the K±K+K– final state between 1.2 and 2 GeV2, as seen in the images above. Note that the value plotted in the figures is the raw asymmetry ARAWCP, and does not include all the small corrections that are included in the numerical results. LHCb physicists are planning further study of this intriguing feature.
The full 2011 data sample was used to obtain this result. LHCb physicists expect to more than triple their data sample this year.