Calorimeter (particle physics)
Encyclopedia
In particle physics
, a calorimeter is an experimental apparatus that measures the energy
of particles
. Most particles enter the calorimeter and initiate a particle shower
and the particles' energy is deposited in the calorimeter, collected, and measured. The energy may be measured in its entirety, requiring total containment of the particle shower, or it may be sampled. Typically, calorimeters are segmented transversely to provide information about the direction of the particle or particles, as well as the energy deposited, and longitudinal segmentation can provide information about the identity of the particle based on the shape of the shower as it develops. Calorimetry
design is an active area of research in particle physics.
, while a hadronic calorimeter is one designed to measure particles that interact via the strong nuclear force. (See types of particle showers for the differences between the two.) The response of a calorimeter can be described in terms of the e/h ratio. This is the measure of how well a calorimeter responds to leptons or photons versus hadrons. Ideally one would want a ratio e/h~1, this condition is called compensation.
A homogeneous calorimeter is one in which the entire volume is sensitive and contributes a signal. Only electromagnetic calorimeters can be homogeneous.
or ZEUS
, the calorimeter works in conjunction with other components like a Central Tracker and a Muon Detector. All the components work together to achieve the objective of reconstructing a physics event.
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 calorimeter is an experimental apparatus that measures the energy
Energy
In physics, energy is an indirectly observed quantity. It is often understood as the ability a physical system has to do work on other physical systems...
of particles
Subatomic particle
In physics or chemistry, subatomic particles are the smaller particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles...
. Most particles enter the calorimeter and initiate a particle shower
Particle shower
In particle physics, a shower is a cascade of secondary particles produced as the result of a high-energy particle interacting with dense matter. The incoming particle interacts, producing multiple new particles with lesser energy; each of these then interacts in the same way, a process that...
and the particles' energy is deposited in the calorimeter, collected, and measured. The energy may be measured in its entirety, requiring total containment of the particle shower, or it may be sampled. Typically, calorimeters are segmented transversely to provide information about the direction of the particle or particles, as well as the energy deposited, and longitudinal segmentation can provide information about the identity of the particle based on the shape of the shower as it develops. Calorimetry
Calorimetry
Calorimetry is the science of measuring the heat of chemical reactions or physical changes. Calorimetry is performed with a calorimeter. The word calorimetry is derived from the Latin word calor, meaning heat...
design is an active area of research in particle physics.
Electromagnetic versus hadronic
An electromagnetic calorimeter is one specifically designed to measure the energy of particles that interact primarily via the electromagnetic interactionElectromagnetism
Electromagnetism is one of the four fundamental interactions in nature. The other three are the strong interaction, the weak interaction and gravitation...
, while a hadronic calorimeter is one designed to measure particles that interact via the strong nuclear force. (See types of particle showers for the differences between the two.) The response of a calorimeter can be described in terms of the e/h ratio. This is the measure of how well a calorimeter responds to leptons or photons versus hadrons. Ideally one would want a ratio e/h~1, this condition is called compensation.
Homogeneous versus sampling
Either of the above types can be made as a sampling calorimeter, in which the material that produces the particle shower is distinct from the material that measures the deposited energy. Typically the two materials alternate. One advantage of this is that each material can be well-suited to its task; for example, a very dense material can be used to produce a shower that evolves quickly in a limited space, even if the material is unsuitable for measuring the energy deposited by the shower. A disadvantage is that some of the energy is deposited in the wrong material and is not measured; thus the total shower energy must be estimated.A homogeneous calorimeter is one in which the entire volume is sensitive and contributes a signal. Only electromagnetic calorimeters can be homogeneous.
Calorimeters in High Energy Physics Experiments
Most large particle physics experiments use some form of calorimetry. In large colliding experiments like ATLASAtlas
An atlas is a collection of maps; it is typically a map of Earth or a region of Earth, but there are atlases of the other planets in the Solar System. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats...
or ZEUS
Zeus
In the ancient Greek religion, Zeus was the "Father of Gods and men" who ruled the Olympians of Mount Olympus as a father ruled the family. He was the god of sky and thunder in Greek mythology. His Roman counterpart is Jupiter and his Etruscan counterpart is Tinia.Zeus was the child of Cronus...
, the calorimeter works in conjunction with other components like a Central Tracker and a Muon Detector. All the components work together to achieve the objective of reconstructing a physics event.