Are the "Geant4 simulation counts" (counts obtained with the "Geant4 Hits") a good estimate of the counts obtained in the experiment?

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Hi, Are the “Geant4 simulation counts” (counts obtained with the “Geant4 Hits”) a good estimate of the counts obtained in the experiment?. Thanks

Geant4 Version: 11.2.1
Operating System: Windows 10
Compiler/Version: Visual Studio 2022
CMake Version:3.29.0-rc2

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That depends on what you, and your experiment, mean by “counts” or “hits.” A tracking detector will likely record hits that correspond well to individual Geant4 hits (energy deposits), but a calorimeter or bolometer will not. The detector response will be a sum of a large number of Geant4 hits, convolved with response functions for the electronic readout systems.

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Ok, thanks for your reply. By “counts“ I mean energy deposits in an element (a specific volume) of the detector; therefore, the “hits“ in my Geant4 simulation would be energy deposits in an element of the detector; therefore, my detector (a gamma ray detector) would be a calorimeter, right?. Based on what you say about the detector response, Could it also be said that the detector response is a histogram of Counts versus Energy?

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Hello,

so a Hit is a snapshot of the physical interaction of a track in the sensitive detector. In it several information are stored e.g. the energy deposition of the step.

Let’s assume you have one photon/particle that interacts (deposits energy) more than one time in your detector volume. Do you increase the count once for every interaction altough it is just one particle?

Do you want to count particles or number of interactions?
If you want to count particles then NO the number of hits is (in most of the cases i can imagine) not equal to the number of particles. (Edit: previously i wrote “Hits” here which makes no sense)

You can verify your “counting” by generating a fixed number of particles (let’s say 1000) and if you count the exact number, then you are counting particles.

Regards
Max

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Ok, thank you for all the information. I’ll keep that in mind. Regarding your questions:

1.- Do you increase the count once for every interaction altough it is just one particle?, Answer: I am interested in “gamma ray / particle counts”, in other words, I am interested in the energy deposits of each gamma particle in a specific volume of the detector, therefore, the answer is Yes; What is your opinion regarding my answer?

2.- Do you want to count particles or number of interactions?, Answer: I think I would be interested in counting the number of interactions (energy deposits) of the gamma particles. In my case, I think that would be a “Geant4 Hit”.

Regarding the last paragraph of your previous post, Could it be said that it´s easier to count the number of particles than to count the number of interactions (using Sensitive detectors and Hits)?

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Hello again,

This would be the total energy deposit of a particle in your volume by adding up every single energy deposit (Hit) along its track but increasing the particle count by only one.

This would be increasing the counter for the same particle each time it does an interaction.

There are examples that show how both can be done. You can do both an compare the result.

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Hello, thanks for your opinions / comments.
So, I’m going to take a look at the Geant4 examples related to this topic, and also run simulations related to this topic; Which Geant4 examples (basic, extended or advanced) (related to this topic) would you recommend I start looking at?