Search for <i>CP</i> violation in D° → K₀^SK₀^S decays in proton–proton collisions at √𝒔 = 13 TeV

Abstract

A search is reported for charge-parity <i>CP>/i> violation in D° → K<sub0</sub>^SK<sub0</sub>^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*⁺ → D°π⁺ and D*⁻ → D̅⁰π⁻. The <i>CP>/i> asymmetry in D° → K<sub0</sub>^SK<sub0</sub>^S is measured to be <i>A</i>_<i>CP>/i>(K<sub0</sub>^SK<sub0</sub>^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 the <i>CP>/i> asymmetry in the D° → K<sub0</sub>^Sπ⁺π⁻ decay. This is the first <i>CP>/i> asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state.