Orateur
Description
Many next-to-leading order QCD predictions are available through Monte Carlo (MC) simulations. Usually multiple CPU-hours are needed to calculate the physical predictions at a feasible precision and are therefore impractical for global PDF analyses. This problem is solved by a process known as "gridding": The values of the hard-scattering cross-section are calculated only once with the MC program, and then interpolated and stored in look-up tables (grids) of the kinematical variables. To obtain the physical predictions, they are convoluted with the PDFs (e.g. during the fitting stage in a PDF global analysis), which takes a tiny fraction of the time needed to calculate the MC results. This is possible with PineAPPL, a new library tackling the aforementioned process of grid creation and convolution. In this work, we use PineAPPL to grid the predictions for open heavy-flavor production in the general-mass variable-flavor-number scheme (GM-VFNS). In the GM-VFNS, the differential cross-section interpolates between the fixed-flavor-number scheme (FFNS) and the zero-mass variable-flavor-number scheme (ZM-VFNS). These are each only valid in different kinematical regions, in which the GM-VFNS cross-section reproduces the FFNS and ZM-VFNS as the limiting cases of high energies and small masses, respectively. Better than per-mille agreement is achieved between the grids and the MC predictions, while at the same time not substantially increasing the time of the MC calculations.
