Digital Signal Processing Reference
In-Depth Information
Fig. 7
Post-collision particles can be identified as belonging to one of five categories based on
their interaction with the detector's different sensors. Image Copyright CMS Experiment at CERN
5.1
Particle Identification
A particle accelerator's sensors record various measurements from the particles
created in high-energy collisions. A primary function of triggering systems is to
process sensor data and partially reconstruct key information about these particles.
Particles can be identified by observing their interactions with different sensor types.
Some particles, like those with magnetic charge, will deflect in a magnetic field.
Some will only be absorbed by specific materials. Others will pass through most
materials without interacting with them. The interaction of various particles and the
To better understand the processing of this sensor data, it may be useful to
view it as similar to an image processing problem. Collectively, the sensor data
forms the image. Each sensor location can be viewed as a “pixel”, and data from
different sensor types can be viewed as separate channels in each pixel. In the case of
CMS's Electromagnetic Calorimeter (ECAL) and Hadron Calorimeter (HCAL), the
incoming sensor data forms a 4-Kilopixel image, since both the ECAL and HCAL
have a 4096-sensor grid. Identifying specific particle types is now similar to the
problem of identifying objects in a picture. Two of the particle types that need to
be identified are electrons and photons. As Fig.
7
shows, electrons and photons are
absorbed by the ECAL. These particles are small; their energy is deposited only
to the image processing analogy, this process is akin to the problem of finding every
instance of two adjacent pixels in a 4-Kilopixel image wherein green makes up more
