  The ALICE detector at the LHC (A Large Ion Collider Experiment) will carry
out comprehensive measurements of high energy nucleus-nucleus collisions, in
order to study QCD matter under extreme conditions and the phase transtion
between con\"ined matter and the Quark-Gluon Plasma (QGP). This report presents
our current state of understanding of the Physics Performance of the large
acceptance Electromagnetic Calorimeter (EMCal) in the ALICE central detector.
The EMCal enhances ALICE's capabilities for jet measurements. The EMCal enables
triggering and full reconstruction of high energy jets in ALICE, and augments
existing ALICE capabilities to measure high momentum photons and electrons.
Combined with ALICE's excellent capabilities to track and identify particles
from very low pT to high pT, the EMCal enables a comprehensive study of jet
interactions in the medium produced in heavy ion collisions at the LHC.
