Successful Installation of the CMS Pixel Tracker at the Large Hadron Collider

The pixel tracker is the subdetector that is closest to the beamline in the CMS experiment.
Credit: CERN

After more than two years of maintenance and upgrades, the Pixel Tracker has been installed at the center of the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC) and is now ready for commissioning.

Of all the CMS subdetectors, the Pixel Tracker is the closest to the interaction point (IP) – the point of collision between the proton beams. In the core of the detector, it reconstructs the paths of high-energy electrons, muons, and electrically charged hadrons, but also the decay of very short-lived particles such as those containing beauty or “b” quarks. Those decays are used, among other things, to study the differences between matter and antimatter.

The Pixel Tracker is composed of concentric layers and rings of 1800 small silicon modules. Each of these modules contains about 66,000 individual pixels, for a total of 120 million pixels. The pixels’ tiny size (100×150 μm2) allows the trajectory of a particle passing through the detector to be precisely measured and its origin determined with a precision of about 10 μm.

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