Singularities in the single lepton energy spectrum for precise measuring   mass and spin of Dark Matter particles at the e^+e^- Linear Collider
  We consider models in which stability of Dark Matter particles $D$ is ensured by the conservation of the new quantum number, called D-parity here. Our models contain also charged $D$-odd particle $D^\pm$.   Here I propose the method for precision measuring masses and spin of $D$-particles via the study of energy distribution of single lepton ($e$ or $\mu$) in the process $\epe\to D^+D^-\to DDW^+W^-$ with the observable states {\it dijet + lepton} ($\mu$ or $e$) + {\it nothing}. To determine precisely masses of $D$ and $D^\pm$, it is sufficient to measure the singular points in the lepton energy distributions (upper edge and kinks or peak). After this, even a rough measuring of corresponding cross section allows to determine the spin of $D$ particles.   This approach is free from the difficulties of a well-known methods of measuring the masses via the edges of the energy distribution of dijets, representing $W$, which obliged by inaccuracies in measuring the energies of individual jets. 
Ilya F. Ginzburg
hep-ph hep-ex