What is meant by "electromagnetic energy resolution"?

[Anchovy]

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?

 

[BvU]

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.

 

[mfb]

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.

 

[Anchovy]

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)

 

[Vanadium 50]

In that paper it means the resolution for objects that predominantly deposit energy by electromagnetic processes.

 

[mfb]

That is the energy resolution of the electromagnetic calorimeter.

 

[Anchovy]

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?

 

[mfb]

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.

 

[Anchovy]

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'?

 

[Vanadium 50]

Answered in post #5.

 

[mfb]

I never saw the term "electromagnetic energy resolution" used for a TPC.

 

[Vanadium 50]

It's a liquid argon TPC so photons shower.

 

[mfb]

Ah, right. So we have a calorimeter design.