What is meant by "electromagnetic energy resolution"?

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Discussion Overview

The discussion revolves around the term "electromagnetic energy resolution" as it pertains to detectors in particle physics. Participants explore its definition, context, and implications in various detection methods, particularly focusing on electromagnetic calorimeters and time projection chambers.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions whether "electromagnetic energy resolution" refers to the resolution of energy for electrically charged particles or the resolution achievable through specific detection methods, such as measuring ionization charge versus Cerenkov light.
  • Another participant suggests that the term indicates the accuracy of measuring a particle's energy, emphasizing the importance of identifying decay products and their interactions with detector materials.
  • Several participants note that electromagnetic calorimeters are designed to measure energy deposited by photons and electrons, with one highlighting the context of liquid argon time projection chambers.
  • There is a discussion about whether the term applies exclusively to charged objects, with one participant seeking clarification on its application in time projection chambers, which do not separate electromagnetic and hadronic calorimeters.
  • One participant asserts that the term is used in a specific paper to describe the resolution for objects that predominantly deposit energy through electromagnetic processes.
  • Another participant mentions that hadrons and muons behave differently in calorimeters, which raises questions about the applicability of the term to various particle types.

Areas of Agreement / Disagreement

Participants express differing views on the definition and context of "electromagnetic energy resolution," with no consensus reached on its precise meaning or application across different detector types.

Contextual Notes

Participants reference specific detector designs, such as electromagnetic and hadronic calorimeters, and the implications of using a time projection chamber, indicating that the term's application may depend on the specific experimental setup.

Anchovy
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I'm reading about detectors and seeing the term "electromagnetic energy resolution", but can't find a definition. Is this simply referring to the resolution of the energy of electrically charged particles? Or could it be to do with the resolution achievable through a particular method of detection, for example, measuring ionization charge rather than Cerenkov light (not that photons are any less 'electromagnetic' than electrons really, but whatever) ? Or something else?

And will it typically be referring to the energy that the particle actually has, or the detectable energy that it has deposited?
 
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First impression for the term "electromagnetic energy resolution" is "the accuracy that is achieved when measuring the energy of a particle". The 'simply' part of your post.

In detectors you want to know as much as possible of the decay products: identity (charge and rest mass), and the velocity vector, and as precise as possible.

What you can measure are things like momentum (ionization tracks in a magnetic field), speed (Cerenkov, time-of-flight scintillation counters), total energy (for particles that give off electromagnetic showers in e.g. NaI or BGO crystals). Particles interact differently with the material they encounter in a detector, so these detectors are designed to allow a maximum of identification and tracking for the specific (or general) purposes of the experiment.

So (a second 'yes') sometimes the energy resolution is a construct from indirect measurements: e.g. we have measured the momentum and assume it is a pi+ from time-of-flight.
 
What is the context?
Many detectors have electromagnetic calorimeters (where photons and electrons/positrons deposit their energy in electromagnetic showers) and hadronic calorimeters (similar but for hadrons and hadronic showers), and "electromagnetic energy resolution" sounds like the energy resolution of an electromagnetic calorimeter.
 
mfb said:
What is the context?
Many detectors have electromagnetic calorimeters (where photons and electrons/positrons deposit their energy in electromagnetic showers) and hadronic calorimeters (similar but for hadrons and hadronic showers), and "electromagnetic energy resolution" sounds like the energy resolution of an electromagnetic calorimeter.

The context is liquid argon time projection chambers. For example the term is used in this paper:

Underground operation of the ICARUS T600 LAr-TPC: first results
C. Rubbia
Journal of Instrumentation 6 07011 (2011)
 
In that paper it means the resolution for objects that predominantly deposit energy by electromagnetic processes.
 
That is the energy resolution of the electromagnetic calorimeter.
 
Vanadium 50 said:
In that paper it means the resolution for objects that predominantly deposit energy by electromagnetic processes.

"objects that predominantly deposit energy by electromagnetic processes."

Does that effectively just mean 'charged objects' then?
 
I think Vanadium meant "electromagnet showers".

Electrons and photons. That is a complete list.

Hadrons deposit their energy later (mainly in the hadronic calorimeter), muons don't lose much energy in either calorimeter, neutrinos don't get detected at all, all other particles don't live long enough to reach the calorimeters.
 
mfb said:
I think Vanadium meant "electromagnet showers".

Electrons and photons. That is a complete list.

Hadrons deposit their energy later (mainly in the hadronic calorimeter), muons don't lose much energy in either calorimeter, neutrinos don't get detected at all, all other particles don't live long enough to reach the calorimeters.

What about when the detector is a time projection chamber though? That isn't separated into EM and hadronic calorimeters, rather just a single tank of liquid argon. In that instance would you just treat the term as meaning 'anything charged'?
 
  • #10
Answered in post #5.
 
  • #11
I never saw the term "electromagnetic energy resolution" used for a TPC.
 
  • #12
It's a liquid argon TPC so photons shower.
 
  • #13
Ah, right. So we have a calorimeter design.
 

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