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Particle Flow

The Particle Flow Approach

Traditionally, jet energies have been measured by taking the sum of the energies deposited in the hadronic and electromagnetic calorimeters.  The hadronic calorimeter, having a relatively poor energy resolution, was the limiting the precision of the jet energy measurements.  At the ILC, a highly granular calorimetry system will be used in conjunction with the tracking devices to measure the energy and momentum of every visible particle inside the detector.  The energy of charged hadrons will be measured by the tracking detectors; the energy of photons will be measured by the electromagnetic calorimeter.  The hadronic calorimeter is then used only to measure the energy of neutral hadrons, which carry about 10% of the energy in a jet.  The reduced dependence on the hadronic calorimeter will lead to an unprecedented jet energy resolution at the ILC.

Pandora PFA Image

Particle flow: the highly granular calorimeters of ILD can identify the energy deposit of every visible particle.


For more introductory material, follow this link:


J.-C. Brient, H. Videau, The calorimetry at the future e+ e- linear collider, Proc. of APS/DPF/DBP summer study on the future of particle physics, Snowmass, Colorado, 2002.

M. A. Thomson, Particle Flow Calorimetry and the PandoraPFA Algorithm, Nucl. Instrum. Meth. A 611, 25 (2009).

PandoraPFA wiki

To learn about the software implementation of Particle Flow at ILD, see this link:

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