The precise measurement of hadronic jet energy is crucial to maximise the physics reach of a future Linear Collider. An important ingredient required to achieve this is the efficient identification of photons within hadronic showers. One configuratio
n of the ILD detector concept employs a highly granular silicon-tungsten sampling calorimeter to identify and measure photons, and the GARLIC algorithm described in this paper has been developed to identify photons in such a calorimeter. We describe the algorithm and characterise its performance using events fully simulated in a model of the ILD detector.
In order to profit from the high granularity of the calorimeters proposed for the ILC that are suitable for the Particle Flow Approach, specialised clustering algorithms have to be developped. GARLIC is such an algorithm with the goal to find and ide
ntify pointing photons in the electromagnetic calorimeter. This would help to improve the energy resolution on the photon contribution in jets.
The CALICE prototype for a Si/W electromagnetic calorimeter has been tested in large scale test beams. Several million events with electrons and hadrons of different energies and impact angles have been recorded. The energy resolution has been measur
ed to be (16.6 +- 0.1)%/sqrt(E(GeV)) for the stochastic and (1.1 +- 0.1)% for the constant term with a linearity within the 1% level. The next step will be the construction of a large scale prototype which will take realistic experimental costraints into account. This module will naturally benefit from the experience gained with the first prototype.
