First "data" from LHC—No, it's not the Higgs

Although the Large Hadron Collider (LHC) being built at CERN is not expected to be officially "turned on" until June 2007, a major milestone has been achieved by the ATLAS collaboration—validating the operation of the tile calorimeter (TileCal) detector at the heart of the experiment. As reported at July's Lepton-Photon Symposium at Uppsala University, Sweden, signals generated by cosmic ray particles are the first sign that the detector is working as it should. As shown in image at the left, the passage of a cosmic muon (yellow) is recorded in the barrel section of the TileCal calorimeter. (Calorimeters are standard detectors in large particle accelerators; they absorb particles and measure their energies.)

Because muons are the most penetrating of all particles (except the rarely detectable neutrinos), they tend to stream straight through the mass of the calorimeter without being absorbed. While such cosmic rays are "noise" that must be stripped out of events when the accelerator is turned on and begins taking collision data, the muons' unmistakable straight tracks through the detector indicate that the different detector components are aligned and connected correctly.

The University of Illinois at Urbana-Champaign was one of seven institutions worldwide that collaboratively built the ATLAS TileCal. Led by Professor Steven M. Errede, the Illinois group participated in the early R&D activities and then, beginning in 1996, built and tested about 200 of the TileCal submodules and tested more than 2000 photomultiplier tubes used in the experiment. Overall, about 20 percent of the total five-story ATLAS detector was built and tested here in Urbana before being installed in Switzerland.

ATLAS is the largest collaborative effort ever attempted in the physical sciences—1800 physicists (including 400 students) from more than 150 universities and laboratories in 34 countries are building this colossal experiment. Further information about ATLAS may be obtained from Professor Errede.

Funding for this work was provided by the U.S. Department of Energy. The conclusions presented are those of the researchers and not necessarily those of the DOE.

© Copyright 2003 by the Department of Physics at the University of Illinois at Urbana-Champaign.

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