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Space-like virtualities of partons

  1. Oct 19, 2012 #1
    I used PYTHIA (an event generator) to have parton showers from the process e+ e- → γ*/Z0→q \bar{q}→parton showers (PYEEVT).
    I realized that some partons (gluons or quarks) produced in this process have imaginary masses (Q2=E2-px2-py2-pz2<0), i.e. space-like virtualities.
    As I know, space-like partons usually come from initail state radiation. However, in case of the above process, there is no initial state radiation.
    I don't believe that PYTHIA was wrong because PYTHIA has been corrected and polished much by many people for about thirty years(?).
    Can anybody explain me why the space-like virtualities happened and what they mean?
    I attached a text file for an event list.

    Attached Files:

    Last edited: Oct 19, 2012
  2. jcsd
  3. Oct 19, 2012 #2


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    2017 Award

    Staff: Mentor

    All particles 4-43 are virtual. Why do you expect a positive (real) mass there?
    All particles after 44 look real.
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