This document explains what interpolation grids are and what PineAPPL is.
Interpolation grids store theoretical predictions that are not convolved with PDFs yet. After the predictions have been generated once, the grids can be convolved with arbitrary PDFs in a fraction of a second. This is very advantageous for the following applications:
- PDF set dependence of a prediction. Are the predictions with CT18, MSHT20 and NNPDF3.1 compatible? If they are not, which parts of their PDF sets are responsible for this?
- PDF fits require the evaluation and fit of theory predictions to experimental data with changing PDFs, which are impossible without PDF-independent theory predictions.
PineAPPL is an interpolation library, and provides interfaces to numerical calculations to generate interpolation grids. It is not the only library that does that, as there at least two others: APPLgrid and fastNLO. Distinguishing features of PineAPPL are
- support for arbitrary fixed-order calculations, in particular EW and mixed QCD–EW corrections. Furthermore it aims to
- provide excellent tooling, which is easy to use and provides maximum insight into theory predictions.