Project aim:

The idea of the project was an introduction into what parameter variations are possible in General-Purpose MCs, and to help build intuition on which of these variations can affect which measurements.

Minutes of the discussion on site have been posted on the slack channel. It was also suggested that the discussion can continue between MC developers at the upcoming MCnet meeting.

To get to an introduction, we thought to first give

• as comprehensive as possible list of all possible variations available in each generator

• list of correlations among these variations (as comprehensive as possible)

• for each MC:

1. exact interpretation of name “variation X”, and which phenomena it influences
2. what are the constraints when varying parameters that should not be broken
3. wherever this is possible, suggested ranges of variations
4. disclaimers and “good practice”

It would be ideal if through these lists, we can come to a somewhat common naming convention. This would significantly help in the communication between MC developers and experiments. Currently, the terms “MC uncertainties” or “PS uncertainties” are used in an unclear way, and this project would help towards removing some of this language barrier.

Given a list of variations and their discussion, it would also be extremely valuable to have a

• list of examples (exact meaning of “example” to be defined) that highlight the impact of a (category of) MC variations that are relevant in each case, possibly with plots.

Interested people:

• Simone Amoroso, Helen, Stefan Prestel, Leif Gellersen, Josh McFayden, Christian Reuschle, Carlo Pandini, Enrico Bothmann, Yacine Haddad