Measurement of the time-integrated CP asymmetry in D⁰ →K_S⁰ K_S⁰ decays

measurement of the time-integrated CP asymmetry in D0 → KS 0KS 0 decays is reported. The data correspond to an integrated luminosity of about 2 fb−1 collected in 2015–2016 by the LHCb collaboration in pp collisions at a centre-of-mass energy of 13 TeV. The D0 candidate is required to originate from a D*+ → D0π+ decay, allowing the determination of the flavour of the D0 meson using the pion charge. The D0 → K+K− decay, which has a well measured CP asymmetry, is used as a calibration channel. The CP asymmetryfor D0 → KS 0KS 0 is measured to beACP(D0→KS0KS0)=(4.3±3.4±1.0)%,where the first uncertainty is statistical and the second is systematic. This result is combined with the previous LHCb measurement at lower centre-of-mass energies to obtainACP(D0→KS0KS0)=(2.3±2.8±0.9)%.