LHCb Physicists have also presented results of their search for new physics using the B0d (composed of a beauty antiquark (b) bound with a down quark d) decay into an excited K meson, K*, and a μ+ and μ–. The partial rate as a function of the square of the di-muon invariant mass (q2) and the di-muon forward-backward asymmetry (AFB) can both be affected in many new physics scenarios. The variable AFB indicates whether more or fewer muons of one sign are observed in the forward direction than in the backward direction. The distribution of AFB in function of q2 is shown below.
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The LHCb precision measurements shown in black are in agreement with the Standard Model (SM) theory and indicate for the first time that the asymmetry is changing sign as predicted by the SM. The results of measurements by other experiments are presented in the figure on the right hand side.