Simulations of minimum bias events and the underlying event, MC tuning and predictions for the LHC

Minimum bias and underlying event data from the SppmacronS and the Tevatron have been compared to PYTHIA and PHOJET simulations. The data have been used to tune the PYTHIA multiparton model and good agreement is found. PHOJET also gives good agreement. Predictions are made for the multiplicities in minimum bias and the underlying events at the LHC. PYTHIA predicts increases by factors of order two to three from Tevatron energies, while PHOJET predicts more modest increases by a factor of 1.5. The effect of different levels of underlying event activity on the central jet veto used in Higgs searches in the vector boson fusion channel is investigated.