  Geant4, the leading detector simulation toolkit used in high energy physics,
employs a set of physics models to simulate interactions of particles with
matter across a wide range of energies. These models, especially the hadronic
ones, rely largely on directly measured cross-sections and inclusive
characteristics, and use physically motivated parameters. However, they
generally aim to cover a broad range of possible simulation tasks and may not
always be optimized for a particular process or a given material. The Geant4
collaboration recently made many parameters of the models accessible via a
configuration interface. This opens a possibility to fit simulated
distributions to the thin target experimental datasets and extract optimal
values of the model parameters and the associated uncertainties. Such efforts
are currently undertaken by the Geant4 collaboration with the goal of offering
alternative sets of model parameters, also known as "tunes", for certain
applications. The effort should subsequently lead to more accurate estimates of
the systematic errors in physics measurements given the detector simulation
role in performing the physics measurements. Results of the study are presented
to illustrate how Geant4 model parameters can be optimized through applying
fitting techniques, to improve the agreement between the Geant4 and the
experimental data.
