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Results are presented from a search for CP violation in top quark pair production, using proton-proton collisions at a center-of-mass energy of 13 TeV. The data used for this analysis consist of final states with two charged leptons collected by the CMS experiment, and correspond to an integrated luminosity of 35.9 fb⁻¹. The search uses two observables,$$ \mathcal{O} $$$O$₁and$$ \mathcal{O} $$$O$₃, which are Lorentz scalars. The observable$$ \mathcal{O} $$$O$₁is constructed from the four-momenta of the charged leptons and the reconstructed top quarks, while$$ \mathcal{O} $$$O$₃consists of the four-momenta of the charged leptons and the b quarks originating from the top quarks. Asymmetries in these observables are sensitive to CP violation, and their measurement is used to determine the chromoelectric dipole moment of the top quark. The results are consistent with the expectation from the standard model.

The collective behavior of$$ {\textrm{K}}_{\textrm{S}}^0 $$$K_S^0$and$$ \Lambda /\overline{\Lambda} $$$\Lambda /\overline{\Lambda }$strange hadrons is studied by measuring the elliptic azimuthal anisotropy (v₂) using the scalar-product and multiparticle correlation methods. Proton-lead (pPb) collisions at a nucleon-nucleon center-of-mass energy$$ \sqrt{s_{\textrm{NN}}} $$$\sqrt{s_{\mathrm{NN}}}$= 8.16 TeV and lead-lead (PbPb) collisions at$$ \sqrt{s_{\textrm{NN}}} $$$\sqrt{s_{\mathrm{NN}}}$= 5.02 TeV collected by the CMS experiment at the LHC are investigated. Nonflow effects in the pPb collisions are studied by using a subevent cumulant analysis and by excluding events where a jet with transverse momentum greater than 20 GeV is present. The strange hadronv₂values extracted in pPb collisions via the four- and six-particle correlation method are found to be nearly identical, suggesting the collective behavior. Comparisons of the pPb and PbPb results for both strange hadrons and charged particles illustrate how event-by-event flow fluctuations depend on the system size.