Speaker: Richard (Rick) Field, (University of Florida)
I will review the CDF “underlying event” (UE) studies at the Tevatron starting with the first studies in 2000 and the first Tevatron QCD Monte-Carlo model tune, PYTHIA Tune A. I will discuss the extrapolation of the CDF Tevatron PYTHIA tunes to the LHC energies. CDF UE data at 300 GeV, 900 GeV, and 1.96 TeV can be combined with LHC data at 7 and 13 TeV allowing for a detailed study of the energy dependence of the various components of the UE at five center-of-mass energies. The CDF 300 GeV and 900 GeV data are a result of the “Tevatron Energy Scan” which was performed just before the Tevatron was shut down. The overall “transverse” region of can be divided into the “transMAX” and “transMIN” contributions. The “transMIN” is very sensitive to the multiple parton interaction component (MPI) of the UE, while “transDIF” (“transMAX” minus “transMIN”) is very sensitive to the initial-state and final-state radiation. The “transMIN” and “transDIF” observables have very different energy dependences. The PYTHIA QCD Monte Carlo model tunes do a fairly good (although not perfect) job in describing the energy dependence of “transMIN” and “transDIF”. I have enjoyed very much being involved with the CDF UE measurements at 300 GeV, 900 GeV, and 1.96 TeV, as well as the more recent CMS UE studies 7 and 13 TeV. Combined Tevatron and LHC UE studies will result in improved QCD Monte Carlo models and more accurate simulations of hadron-hadron collisions.