In the Large Hadron Collider (LHC) of CERN protons are accelerated to speeds very near the speed of light in order to be collided. The collisions take place in different detectors placed along the LHC. One of these detectors is called the Compact Muon Solenoid (CMS). The CMS experiment has four main parts. Each part works to detect different particles. The four major components are the Tracker, the Hadron Calorimeter (HCAL), the Electromagnetic Calorimeter (ECAL), and the Muon system.

The Tracker
The CMS tracker contains the worlds largest Silicon Strip Tracker (SST) with 24,244 silicon sensors and 17000 silicon modules. It is 206 square meters and expected to operate up to 10 years. With a highly radioactive environment, the CMS tracker can capture new data every 25 nanoseconds. The tracker is divided into three main detectors: 1) Pixel detector (pixels); 2) Inner tracker (strips); 3) Outer tracker (strips). Each detector has one barrel and two endcaps. The pixel detector is made of a silicon array where each pixel is 150×150 μm. CMS uses CMOS technology connected to each pixel to convert the electric charge detected into a voltage which is read out by the electronics.

The Electromagnetic CALorimeter (ECAL) is the detector withinin the CMS designed to detect particles such as photons and electrons that result from beam collisions. ECAL uses over 80,000 crystals and an array of photodetectors that interact with the particles. This is then converted to stored data that can be used to analyze the particles’ momentum, path, etc.

-Detects hadrons (particles made up of quarks and gluons).
-Staggered tiles to eliminate gaps. Alternating layers of “absorber” and “scintillator”.
-4 parts: Barrel, Outer, Forward, Endcap.
-In HCAL, staggering the materials helps to more effectively slow down the particle. It also helps to more efficiently measure information about the particle. When a particle hits the apparatus, the particle’s energy produces light. The light that is produced represents the amount of energy that the particle had. The light is converted into an electrical signal by a photomultiplier.

Muon System
One of the detector’s most important tasks is the measurement of muons. The muon detection system at CMS is placed on the outside of the detector. There are four muon stations that are used to detect the particle trajectory. There are 1400 muon chambers which consist of 250 drift tubes, 540 cathode strip chambers, and 610 resistive plate chambers. The RPCs provide a fast signal, allowing for quick data filtering.

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