Search for CP violation in D0 → KS0KS0 decays in proton-proton collisions at [Formula: see text].

A search is reported for charge-parity CP violation in D0 → KS0KS0 decays, using data collected in proton-proton collisions at [Formula: see text] recorded by the CMS experiment in 2018. The analysis uses a dedicated data set that corresponds to an integrated luminosity of 41.6 fb-1 , which consists of about 10 billion events containing a pair of b hadrons, nearly all of which decay to charm hadrons. The flavor of the neutral D meson is determined by the pion charge in the reconstructed decays D ∗  +  → D0π+ and D ∗  -  → D¯0π- . The CP asymmetry in D0 → KS0KS0 is measured to be ACP(KS0KS0) = (6.2 ± 3.0 ± 0.2 ± 0.8)% , where the three uncertainties represent the statistical uncertainty, the systematic uncertainty, and the uncertainty in the measurement of the CP asymmetry in the D0 → KS0π+π- decay. This is the first CP asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state.