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Meaning of Scale of an events/process in MonteCarlo

  1. Jul 14, 2013 #1
    Meaning of "Scale" of an events/process in MonteCarlo

    Hi there

    I do have this question - I often hear that "this depends on the scale of the process" for example when it comes to match the matrix-elements with a parton-shower program (I am new to MonteCarlo world)

    so, what does "scale" means ? Is just the Q that is carried out by the produced particle or is what we could define as factorization scale ie Q^2 = m^2(W) + Sum{JetPT(i)}

  2. jcsd
  3. Jul 16, 2013 #2

    There are I guess 3 types of scale present normally.

    The first is the momentum exchange of the process, Q^2. Which is determined by the incoming colliding particles or by a previous branching if you are talking about Parton showering.

    Then there are two un physical scales. Renormalization and factorisation

    This first if these is essentially a momentum cut off for loop integrals.

    The second has to do with factoring some particle splittings into say a proton, as oppose to including it in a matrix element.

    These last two scales are a remnant if the fact we are doing perturbation only to some order. I.e. because we are ignorant to higher orders we haven't calculated.

    Hope this helps
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