Early LHC Underlying Event Data - Findings and Surprises

Understand

The CDF PYTHIA 6.2 Tune DW predictions of the LHC underlying event (UE) data at 900 GeV and 7 TeV are examined in detail.

• The behavior of the UE at the LHC is roughly what we expected.
• The new LHC PYTHIA 6.4 Tune Z1 does an even better job describing the UE data at 900 GeV and 7 TeV.
• However, the modeling of "min-bias" at the LHC (i.e.