Measurement of the effective Bs⁰→K⁺K^- lifetime

A precise determination of the effective B _s ⁰→K ⁺K ^- lifetime can be used to constrain contributions from physics beyond the Standard Model in the Bs0 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 B _s ⁰→K ⁺K ^- lifetime is measured as 1.455±0.046(stat.)±0.006(syst.)ps.