particle physics Particle physics or high energy physics is the study of fundamental particles and forces that constitute matter and radiation. The fundamental particles in the universe are classified in the Standard Model as fermions (matter particles) and ...

, a trigger is a system that uses criteria to rapidly decide which

events Event may refer to: Gatherings of people * Ceremony, an event of ritual significance, performed on a special occasion * Convention (meeting), a gathering of individuals engaged in some common interest * Event management, the organization of ev ...

in a

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 ionizing particles, such as those produced by ...

to keep when only a small fraction of the total can be recorded. Trigger systems are necessary due to real-world limitations in computing power, 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 The Large Hadron Collider (LHC) is the world's largest and highest-energy particle collider. It was built by the European Organization for Nuclear Research (CERN) between 1998 and 2008 in collaboration with over 10,000 scientists and hundr ...

(LHC) has an event rate of 40 MHz (4·10⁷ Hz), and the

Higgs boson The Higgs boson, sometimes called the Higgs particle, is an elementary particle in the Standard Model of particle physics produced by the quantum excitation of the Higgs field, one of the fields in particle physics theory. In the St ...

is expected to be produced there at a rate of roughly 1 Hz. The LHC detectors can manage to permanently store about one thousand events per second. Therefore, the minimum selectivity required is 10⁻⁵, with much stricter requirements for the data analysis afterwards.Lindenstruth, V, and Kisel, I. Overview of trigger systems. Nucl. Instr. and Meth. A 535 (2004) 48-56.

References

Experimental particle physics {{Particle-stub

See also

References