Using a data set corresponding to an integrated luminosity of Support mathImg" data-mathURL="/science?_ob=MathURL&_method=retrieve&_eid=1-s2.0-S0370269316305779&_mathId=si2.gif&_user=111111111&_pii=S0370269316305779&_rdoc=1&_issn=03702693&md5=d3ed4e2b5b9f6fb7dd8b454ad4020fac" title="Click to view the MathML source">3 fb<sup>−1sup>, collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the decay mode, τ<sub>effsub>, is measured to be
τ<sub>effsub>=1.479±0.034 (stat)±0.011 (syst) ps.
Assuming CP conservation, τ<sub>effsub> corresponds to the lifetime of the light mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.