How reliable are MC simulations when it comes to jets?

In summary, there is a reliance on MC-generated jets for tag-and-probing or training BDTs, but there is a concern about their reliability in modelling fragmentation and lepton misidentification. This leads to the need for data-driven methods and control regions to estimate the effects of jets. There may also be some minimal dependence on input MC in evaluating jet energy scale, but this is accounted for in systematic uncertainties. The use of MC is often avoided if possible and can lead to large uncertainties.
  • #1
ChrisVer
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I have been reading in papers here and there, that di/multi-jet MC generated or even other process that have one or more associated jets are used for tag-and-probing or for training several BDTs and so on. Some experiticians (theoreticians who produce experiments) are also relying on how well MCs are simulating the jets.

However I have the impression (through what I've done) that MCs are not so reliable in modelling the fragmentation or in general lepton misidentification. For that reason it's almost always the case in analyses to try and estimate those 'jets' via data-driven methods and by defining several control regions to do so.

How is that affecting people who rely a lot on jets? Or even more, people who study jet calibrations and so on as in:
https://cds.cern.ch/record/2037613/files/ATL-PHYS-PUB-2015-015.pdf
which initiated my question since they seem to take MC jets for their analysis
 
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  • #2
Can you specify what you mean by MC?

Do you mean a full simulation of events including pileup, detector response etc.? Or do you mean just a full pp event with a hard process, Parton shower and hadronisation?

There might always be some minimal dependence on the input MC on the evaluation of the jet energy scale etc. But such dependence should be accounted for in the systematic uncertainties.
 
  • #3
I guess I was referring to the whole simulation... but I think even the parton showers are not very reliable.
 
  • #4
ChrisVer said:
which initiated my question since they seem to take MC jets for their analysis
You can rarely work completely without MC, but in general it is avoided as much as possible, and where it is used it often leads to large systematic uncertainties.
 

1. How do MC simulations accurately model jets?

MC simulations use statistical methods to generate random numbers and simulate the behavior of particles in a jet. These simulations take into account various factors such as energy, momentum, and interactions between particles to accurately model the behavior of jets.

2. How reliable are MC simulations compared to other methods?

MC simulations are considered to be a reliable method for studying jets because they take into account a wide range of factors and can accurately model complex systems. However, they are not the only method used and may have limitations depending on the specific scenario being studied.

3. Can MC simulations accurately predict real-world jet behavior?

MC simulations can provide valuable insights into the behavior of jets and can be used to make predictions about real-world scenarios. However, the accuracy of these predictions depends on the quality of the input data and the complexity of the system being studied.

4. What are the limitations of MC simulations in studying jets?

MC simulations may have limitations in certain scenarios, such as when dealing with very high energies or when studying certain types of interactions between particles. Additionally, the accuracy of the simulations can be affected by the assumptions and approximations used in the model.

5. How can the reliability of MC simulations for jets be tested?

The reliability of MC simulations for jets can be tested by comparing the results of the simulation with experimental data or other theoretical models. Additionally, sensitivity analyses can be performed to assess the impact of different parameters on the results of the simulation.

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