Study of radiation between jets, for colour singlet and colour octet exchange

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The idea is to study the difference between the exchange of colour singlets and coloured objects in events with jets separated by large rapidity intervals, to be validated by early LHC data.

From the theory point of view, we plan to use an FKL approach to very high-order processes where a gluon ladder is emitted between the two main jets. An important topic is the possibility (?) of matching these calculations to parton shower MCs.

Experimentally, we will study observables to distinguish the two cases, also in the presence of the underlying event, so developing techniques to subtract it and distinguish it from the hard QCD radiation.

  • theory: J.Andersen, P.Skands
  • experiment: M.Campanelli, P.Francavilla, P.Loch, J.Weng

Forward-Backward Correlations (with tracks and ET at central eta, and ET only at high eta) to probe relative sizes of short-distance vs long-distance correlations (roughly gauges the amount of particle production due to long-distance soft strings vs the amount produced by shorter-distance phenomena, such as radiation), see:

Plans toward the experimental proceedings:

  • Study of the density of jets using the area method, to discriminate between jets mainly coming from UE and from radiation (P.Francavilla)
  • Study of long-distance over short-distance fluctuations of the UE jets (see previous references) (P.Loch)
  • Study of rapidity gaps, after subtraction of underlying event. Comparison of activity in the various gap regions in eta and phi, to region between gap and beam line. Collective vs local effects (M.Campanelli, J.Weng)

Plan to produce common datasets using Herwig (where it is hard to get the information on the parton) and Pythia (where we do not know if there is a proper description of colour singlet states ;-)

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