A search is reported for charge-parity CP violation in D0 → K0
SK0
S decays, using data collected in proton–
proton collisions at √s = 13 TeV 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∗+ → D0
π+ and
D∗− → D0
π−. The CP asymmetry in D0 → K0
SK0
S is measured to be ACP(K0
SK0
S) = (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 theCP asymmetry in the D0 → K0
Sπ+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
