LHCb closes in on CP violation in the Bs system

LHCb physicists have presented their final results from the LHC’s Run 1 for φs - the CP-violating phase in the Bs system

LHCb physicists have presented their final results from the LHC’s Run 1 for φs - the CP-violating phase in the Bs system.

The value of φs is precisely predicted in the Standard Model and sets the scale for CP violation - the difference between properties of matter and antimatter for Bs mesons. The predicted value is small and therefore the effects of new physics could change its value significantly. The measurement of φs is one of the most important goals for the LHCb experiment.

In their latest analysis, the LHCb collaboration used 96 000 B0s → J/ψ K+K- decays collected during 2011 and 2012. The result, φs = - 0.058 ± 0.049 ± 0.006 rad, is the most precise measurement of φs to date. When combined with the recent final Run 1 measurement of the φs that used B0s → J/ψ π+π- decays, the results from the two analyses give a final value of φs = - 0.010 ± 0.040 rad. This is the most precise value of φs and is consistent with the Standard Model prediction of φs = - 0.0363 ± 0.0013 rad. The parameter region in which new physics could still hide is now even smaller than before.

Read more: "φs: CP violation in the Bs system — looking for a chink in the armour of the Standard Model"