  A high-energy e+e- collider, such as the ILC or CLIC, is arguably the best
option to complement and extend the LHC physics programme. A lepton collider
will allow for exploration of Standard Model Physics, such as precise
measurements of the Higgs, top and gauge sectors, in addition to enabling a
multitude of New Physics searches. However, physics analyses at such a collider
will place unprecedented demands on calorimetry, with a required jet energy
resolution of \sigma(E)/E < 3.5%. To meet these requirements will need a new
approach to calorimetry.
  The particle flow approach to calorimetry requires both fine granularity
detectors and sophisticated software algorithms. It promises to deliver
unparalleled jet energy resolution by fully reconstructing the paths of
individual particles through the detector. The energies of charged particles
can then be extracted from precise inner detector tracker measurements, whilst
photon energies will be measured in the ECAL, and only neutral hadron energies
(10% of jet energies) will be measured in the HCAL, largely avoiding the
typically poor HCAL resolution.
  This document introduces the Pandora particle flow algorithms, which offer
the current state of the art in particle flow calorimetry for the ILC and CLIC.
The performance of the algorithms is investigated by examining the
reconstructed jet energy resolution and the ability to separate the hadronic
decays of W and Z bosons.
