Coherent gen particles and reco particles order

[l-cadamuro]

Currently the selected jets and the gen particles (H1, H2, and bb decay products) are ordered independently.
As a result there is no meaningful way to associate reco --> gen in the output tree (e.g., to check if I selected the correct pair of reco jets coming from the same Higgs decay).
An order needs to be defined:

1. either re-order gen to follow reco (opposite is not a good solution, given we will process data and bkg)
2. special configuration of the skimmer to align gen to reco if requried by the user (e.g., gen 1 can be set if and only if reco1 is corresponding). A bit cumbersome and gives limited info
3. Link reco to gen in a meaningful way, e.g. recoLink = 21 could mean gen_H2_b1 (and also contain a -1 is nothing is matched). Requires some if-else when reading the tree but can be good enough for studies

Probably solution 3 is the best one

[l-cadamuro]

NOTE: should possibly also match the VBF partons