Definition of Track and Vertex

• fragment : The set of continous 3(or more) hits in one plane, which would be the candidate of the 2D-projection of real track
• track : The combination of X and Y fragments, which would be the candidate of the real 3D-track
• vertex : We have 3 kinds of vertices.
  1. The intersection point of 2(or more) tracks. (See Fig. 3(a),(b))
  2. For single track(which doesn't intersect with other tracks), the extrapolated point to the mid of the closest water tank of the track. (See Fig. 3(c))
  3. For the entering track to the scifi volume, the entering point. (See Fig. 3(d))