  The granularity of calorimeter has been revolutionary boosted for future
collider experiments. The calorimeter has been pushed to a stage that the sub
structure of showers especially hadronic showers can be recorded to a high
precision. New reconstruction algorithms are expected from these informations.
  Following the idea that shower follows the topology of the tree, we developed
Arbor, a Particle Flow Algorithm framework. Tested on both simulated data and
test beam data, it can successfully separate nearby showers. It has comparable
jet energy resolution the best PFA algorithm for International Linear Collider.
More importantly, Arbor successfully tags the sub shower structure such as the
trajectory of charged particles generated in shower cascade, enabling new
approaches for event reconstruction with high granularity calorimeter.
