How chips helped discover the Higgs boson at CERN

Abstract

Integrated circuits and devices revolutionized particle physics experiments, and have been a cornerstone in the recent discovery of the Higgs boson by the ATLAS and CMS experiments at the Large Hadron Collider at CERN. Particles are accelerated and brought into collision at specific interaction points. Detectors are giant cameras, about 40 m long by 20 m in diameter, constructed around these interaction points to take pictures of collision products as they fly away from the collision point. They contain millions of channels, often implemented as reverse biased silicon pin diode arrays covering areas of up to 200 m2 in the center of the experiment, generating a small (~1fC) electric charge upon particle traversals. Integrated circuits provide the readout, and accept collision rates of about 40 MHz with on-line selection of potentially interesting events before data storage. Power consumption directly impacts the measurement quality as it governs the amount of material present in the detector. Radiation tolerance has to exceed space requirements by orders of magnitude. The presence of tens of thousands of chips in a single system requires special attention to uniformity, robustness and redundancy.