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The ALICE Experiment at LHC

General Description

Work associated with the LHC ALICE experiment is a central part of the ORNL group's program since 2005 (see the ALICE homepage for general info about the experiment).

ALICE (A Large Ion Collider Experiment) is a dedicated heavy ion experiment at the LHC. The goal of the experiment is to study strongly interacting matter at extreme energy densities (QCD thermodynamics). Statistical QCD predicts that, at sufficiently high densities, there will be a transition from hadronic matter to a plasma of deconfined quarks and gluons - a transition which in the early universe took place about 100 micro-seconds after the Big Bang. The study of nuclear collisions at high energies utilizes methods and concepts from both nuclear and high energy physics constituting a new and interdisciplinary approach in investigating matter and its interactions.

Detailed Description

The ALICE collaboration built a dedicated, general-purpose detector that will utilize the full potential of the LHC programme including both nucleus-nucleus and proton-proton collisions. Its design is based on the experiencies gained with the earlier programs at CERN and BNL. ALICE will address a majority of known sensitive observables like hadrons, di-leptons and photons. The ALICE detector will be the only dedicated heavy ion experiment at LHC and its design therefore was conservative and robust to be able to observe most of the signals that look promising today for the QGP formation.

The figure above shows the ALICE experiment. The detector is contained in a big magnet of about 6 meters radius. The detector must have the capability of detecting the produced particles with very high precision. This requires different systems of specially designed detectors based on very advanced technologies.

The ALICE-USA collaboration is participating in ALICE with the construction and operation of a large acceptance electromagnetic calorimeter (EMCal). The EMCal will be essential to study properties of the produced matter. In particular, it will enable 1) an understanding of the energy loss of partons (fast gluons and heavy quarks) in the QCD medium through measurement and triggering on photons, π0, electrons, and jets, and 2) an investigation of the response of the medium to the passage of high energy partons.

Technical Description

Since the inception of the ALICE EMCal project, the ORNL group has had full responsibility for the design, procurement, production, testing, and deployment of all components of the EMCal readout electronics, including associated services. The ORNL group also led the effort to qualify the EMCal detector and electronics performance in test beam measurements at Fermilab in 2005 and at CERN in 2007 and 2010, and to develop the cosmics calibration procedures used at the EMCal super module assembly sites. The ORNL group has also had primary responsibility for the integration of the EMCal readout and trigger into ALICE, for the online software, and for the commisioning of the EMCal super modules after installation in ALICE. ORNL group staff members have been stationed at CERN since 2007 to work on the ALICE project and have provided leadership and mentoring for undergraduate and graduate students sent to CERN from ALICE-USA universities. The ORNL group is solely responsible for the π0 and η analysis with the 7 TeV p+p data set taken in 2010 and 2011, and has worked closely with UTK colleagues on the transverse measurements in p+p and Pb+Pb from the 2010 and 2011 data sets.

For More Information

The following links will let you learn more about this topic:

ALICE public homepage
ALICE internal homepage


Vince Cianciolo, cianciolotv at ornl.gov
David Silvermyr, silvermy at ornl.gov