Umbilicity and characterization of Pansu spheres in the Heisenberg group
  For $n\geq 2$ we define a notion of umbilicity for hypersurfaces in the Heisenberg group $H_{n}$. We classify umbilic hypersurfaces in some cases, and prove that Pansu spheres are the only umbilic spheres with positive constant $p$(or horizontal)-mean curvature in $H_{n}$ up to Heisenberg translations. 
Jih-Hsin Cheng, Hung-Lin Chiu, Jenn-Fang Hwang, and Paul Yang
math.DG