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A How reliable are MC simulations when it comes to jets?

  1. Jul 16, 2016 #1


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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:
    which initiated my question since they seem to take MC jets for their analysis
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  3. Jul 18, 2016 #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.
  4. Jul 18, 2016 #3


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    I guess I was refering to the whole simulation.... but I think even the parton showers are not very reliable.
  5. Jul 18, 2016 #4


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    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.
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