Direct and mixing-induced CP-violating asymmetries in B0
s → K+K− decays
are measured for the first time using a data sample of pp collisions, corresponding to an
integrated luminosity of 1.0 fb−1
, collected with the LHCb detector at a centre-of-mass
energy of 7 TeV. The results are CKK = 0.14 ± 0.11 ± 0.03 and SKK = 0.30 ± 0.12 ± 0.04,
where the first uncertainties are statistical and the second systematic. The corresponding
quantities are also determined for B0 → π
+π
− decays to be Cππ = −0.38±0.15±0.02 and
Sππ = −0.71 ± 0.13 ± 0.02, in good agreement with existing measurements.