  Normalized differential cross sections for top quark pair production are
measured in the dilepton (e$^+$e$^-$, $\mu^+\mu^-$, and $\mu^\mp$e$^\pm$) decay
channels in proton-proton collisions at a center-of-mass energy of 13 TeV. The
measurements are performed with data corresponding to an integrated luminosity
of 2.1 fb$^{-1}$ using the CMS detector at the LHC. The cross sections are
measured differentially as a function of the kinematic properties of the
leptons, jets from bottom quark hadronization, top quarks, and top quark pairs
at the particle and parton levels. The results are compared to several Monte
Carlo generators that implement calculations up to next-to-leading order in
perturbative quantum chromodynamics interfaced with parton showering, and also
to fixed-order theoretical calculations of top quark pair production up to
next-to-next-to-leading order.
