Measurement of the Effective B0s → K+ K− Lifetime

A precise determination of the effective B0s → K+ K− lifetime can be used to constrain contributions from physics beyond the Standard Model in the B0s meson system. Conventional approaches select B meson decay products that are significantly displaced from the B meson production vertex. As a consequence, B mesons with low decay times are suppressed, introducing a bias to the decay time spectrum which must be corrected. This analysis uses a technique that explicitly avoids a lifetime bias by using a neural network based trigger and event selection. Using 1.0 fb^−1 of data recorded by the LHCb experiment, the effective B0s → K+ K− lifetime is measured as 1.455 ± 0.046(stat.) ± 0.006(syst.) ps.