EA propagation: meeting minutes 4/01/10

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A.Accardi, H.Avakian, R.Dupre, G.Gilfoyle, M. Lamont, T.Mineeva

Next Meeting: Thu, Apr 15 at 1pm


Raphael discussed his first results using the PyQM Monte Carlo he is developing, see his notes [1]. PyQM in short is Pythia + energy loss + Lund fragmentation.

Results and issues

  • The effect of Fermi motion is negligible in the attenuation ratio RM(z) and RM(ν). In RM(pT) it is felt only at large pT, where RM does not seem to go back to 1. This is a bit surprising, but may be an illusion of the poor statistics.
    • Raphael may plot the pT distribution on the proton to see what shape and what average pT it has to start with. It is supposed to have a power law tail at large pT, which would require RM(pT)--> 1 at large pT.
  • We also have doubts about how to simulate the pT broadening. Right now, we an average <pT^2> isproportional to the enrgy loss rate -dE/dx is assigned to the parton, see Eq.(1). However, in some cases, this is larger than the longitudinal parton momentum.
    • The problem may be related to the fact that Eq.(1) is for singe gluon radiation, whereas the quenching weights assume a Poisson distributions od the radiated gluons.
    • We should also check the literature on MC implementations of energy loss in Heavy Ion Collisions, which for sure discuss the problem
    • Other ideas?
  • Diffractive pion production: no nuclear effects are included in diffractiv epion production, whence the peak at large z visible in Figure 2. Considering only the DIS component removes the peak, and leads to results resembling HERMES.
    • Question: how does HERMES correct for diffractive pions?
  • Gluon energy loss: Pythia produces a fair amount of gluons, likely stemming from final state radiation off the struck quark (Abhijit, please check!). How should their energy loss be treated? If they can be considered part of the hard scattering, they will be treated teh same as quarks, otherwise, we may overestimate their path length.
    • Do Arleo's quenching weights include gluons?
  • The 'z', 'ν' slope of 'RM' seems a bit smaller than in HERMES data.
  • The ball park qhat to describe HERMES data is >~0.5 GeV^2/fm, compatibly with Alberto's computations

[2] (page )

  • The

Next steps

  • Detailed comparison to HERMES data, extraction of qhat
  • Studies at EIC


Harut is interested in jets in e+p, e+A as a probe of TMDs and intrinsic parton transverse momentum. The questions is how well are jet measurable at EIC, in particular

  • Where do jets end up in teh detctor ?
  • What is the pT resolution? (pT here is relative to γ*

We need to consult the literature:

  • There has been some work on EIC jets in e+p by G.Soyez
  • Jets at HERA ??

Tasks (new and old)

  • Aji: contact C.Loizides for PQM in Q-Pythia
  • Harut: check literature on jets
  • Raphael:
    • continue studies with PyQM at HERMES and EIC
    • Check literature on MC implementations of pT induced by energy loss
  • Volounteers needed: implementing the cold nuclear medium in Q-Pythia in collaboration with M.Ploszkon and C.Loizides at LBL.
  • Taya: calculate particle production rates with Lepto as a cross-check of Raphael's table [3]