particle physics Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...

, a trigger is a system that uses criteria to rapidly decide which events 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 elementary particle, particles, such as t ...

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 The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose formal expression in terms of SI base u ...

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 accelerator. It was built by the CERN, European Organization for Nuclear Research (CERN) between 1998 and 2008, in collaboration with over 10,000 scientists, ...

(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 excited state, quantum excitation of the Higgs field, one of the field (physics), fields in particl ...

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