Event generator tunes obtained from underlying event and multiparton scattering measurements

Area of Science:

• High Energy Physics
• Computational Physics

Background:

• Underlying-event (UE) modeling in Monte Carlo event generators (Pythia8, Pythia6, Herwig++) is crucial for precise physics predictions.
• Existing UE models require updated parameters (tunes) to accurately describe experimental data.

Purpose of the Study:

• To develop new sets of parameters for UE models using various parton distribution functions.
• To constrain UE model parameters by fitting to experimental data from the Compact Muon Solenoid (CMS) and Collider Detector at Fermilab (CDF) experiments.
• To improve predictions for proton-proton collisions at 13 TeV.

Main Methods:

• Constructed new parameter sets ("tunes") for Pythia8, Pythia6, and Herwig++.
• Performed combined fits to CMS proton-proton UE data at 7 TeV and CDF proton-antiproton UE data at 1.96 TeV.
• Investigated consistency between parameters derived from UE observables and those from double-parton scattering processes.

Main Results:

• Achieved improved predictions for proton-proton collisions at 13 TeV.
• Demonstrated consistency between parameters from UE and double-parton scattering fits.
• Presented comparisons of UE tunes to minimum bias, multijet, and Drell-Yan observables at 7 and 8 TeV.

Conclusions:

• The developed UE tunes provide enhanced accuracy for Monte Carlo simulations.
• The study validates the underlying-event models and their parameterization for future high-energy physics analyses.
• Predictions for minimum bias and underlying-event observables at 13 TeV are now more reliable.