Speaker
Summary
The ALICE Experiment (A Large Ion Collider Experiment) aims to study the
properties of quark-gluon matter using Pb-Pb collisions at a center of mass
energy (per nucleon pair) of sqrt(sNN) = 5.5 TeV with the Large Hadron Collider
(LHC) at CERN.
The EMCAL consists in a large area electromagnetic calorimeter able to extend
the measured momentum range of photons and electrons by over an order of
magnitude. In addition, the EMCAL will enhance the capability of the overall
ALICE setup to perform better jet reconstruction by measurement of the
neutral energy component of jets, photons and neutral pions. The EMCAL will
also produce a fast high-pT trigger: the anticipated minimum bias average Pb-
Pb interaction rate is very high (around 8 kHz), thus a fast high-pT trigger will
provide an enhancement in high PT events in central collisions.
The EMCAL covers a geometrical region from -0.7≤eta≤0.7 (in pseudo-rapidity
eta) and 120deg in the azimuthal angle phi. In particular, the phi-coverage of
the EMCAL has been chosen to allow the detection of gamma-jet events in
coincidence with the other ALICE complementary calorimeter, the PHOS.
The EMCAL is a modular sampling calorimeter: it can measure showers up to 20
radiation lengths. Each module is composed by 4 towers of a Pb-scintllator
sandwich (shashlik). The shape of the basic module is tapered to allow a
projective geometry of the final assembly with respect to the interaction point.
An assembly of 12x24 modules is called a super-module. The complete EMCAL is
a high granularity detector containing 11 super modules for a total of 12.672
towers.
An independent optical readout of each tower is provided using wavelength
shifting fibers coupled to an APD (Avalanche Photo Diod). The APD readout was
chosen since the EMCAL has to operate in a high B-field environment created
by the solenoidal magnet. The gain of the APD is monitored using LED activated
scintillator installed on into each module.
