Trigger (particle physics)
Encyclopedia
In particle physics
, a trigger is a system that uses simple criteria to rapidly decide which events
in a particle detector
to keep when only a small fraction of the total can be recorded. Trigger systems are necessary due to real-world limitations in data storage capacity and rates. Since experiments are typically searching for "interesting" events (such as decays of rare particles) that occur at a relatively low rate, trigger systems are used to identify the events that should be recorded for later analysis. Current accelerators have event rates greater than 1 MHz and trigger rates that can be below 10 Hz. The ratio of the trigger rate to the event rate is referred to as the selectivity of the trigger. For example, the Large Hadron Collider
(LHC) is anticipated to have an event rate of 1 GHz (109 Hz), and the Higgs boson
is expected to be produced there at a rate of at least 0.01 Hz. Therefore the minimum selectivity required is 10−11.
Particle physics
Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...
, a trigger is a system that uses simple criteria to rapidly decide which events
Event (particle physics)
An event in particle physics describes one set of particle interactions occurring in a brief span of time, typically recorded together. At modern particle accelerators this refers to the interactions that occur as a result of one beam crossing inside a detector....
in a particle detector
Particle detector
In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify high-energy particles, such as those produced by nuclear decay, cosmic radiation, or reactions in a...
to keep when only a small fraction of the total can be recorded. Trigger systems are necessary due to real-world limitations in data storage capacity and rates. Since experiments are typically searching for "interesting" events (such as decays of rare particles) that occur at a relatively low rate, trigger systems are used to identify the events that should be recorded for later analysis. Current accelerators have event rates greater than 1 MHz and trigger rates that can be below 10 Hz. The ratio of the trigger rate to the event rate is referred to as the selectivity of the trigger. For example, the Large Hadron Collider
Large Hadron Collider
The Large Hadron Collider is the world's largest and highest-energy particle accelerator. It is expected to address some of the most fundamental questions of physics, advancing the understanding of the deepest laws of nature....
(LHC) is anticipated to have an event rate of 1 GHz (109 Hz), and the Higgs boson
Higgs boson
The Higgs boson is a hypothetical massive elementary particle that is predicted to exist by the Standard Model of particle physics. Its existence is postulated as a means of resolving inconsistencies in the Standard Model...
is expected to be produced there at a rate of at least 0.01 Hz. Therefore the minimum selectivity required is 10−11.
See also
- ATLAS trigger system
- CMS trigger