[ φs = -0.002 ± 0.083 ± 0.027 rad]
LHCb physicists have reported today at the Rencontres de Moriond EW conference important progress in measurement of the difference between properties of matter and antimatter for the strange beauty Bs mesons. The new results improve on those presented at the summer 2011 conferences. The size of this difference is controlled by the parameter φs, which is predicted to be small in the Standard Model. However, effects of new particles not predicted by the Standard Model can make the measured value much larger. The progress is shown in the image below: the remaining allowed region is shown in yellow and compared to the previous results from LHCb in blue, and from CDF and D0 experiments in green and red, respectively.
click the image for higher resolution
In the mysterious world of quantum mechanics the strange-beauty meson Bs matter antimatter system is alternatively described as a heavy and light mass Bs meson system. The mass difference Δms determinates the matter antimatter oscillation frequency, see 15 march 2011 news. The difference of their lifetimes was measured together with the value of φs. Since it was not previously know if the heavier or lighter Bs mesons live longer, LHCb physicists have obtained two possible values for φs corresponding to two blue regions in the image above. (The axis label ΔΓs corresponds to the difference of inverse lifetimes between the heavy and light Bs meson, physicists call it width (Γ) difference.) Recently LHCb physicists have succeeded to measure that the heavier strange-beauty Bs mesons live longer and in this way eliminated one of two blue regions in the image. Sophisticated quantum mechanical interference effects were used in this measurement. Experts can read details of the analysis in the published article.
The full sample of data collected in 2011, three times larger than that used in summer 2011, was used to obtain the result
φs = -0.001 ± 0.101 ± 0.027 rad using Bs decays into into a J/ψ meson and a φ meson; combining it with the measurement of the Bs decay into J/ψ and f0(980) LHCb physicists have obtained the final result φs = -0.002 ± 0.083 ± 0.027 rad.
2012 data taking period will start soon. Search for new physics in the small yellow region will continue.