Fix jet matching with Pythia Versions later than 8.3

[bistapf]

BEGINRELEASENOTES

• Add the missing else block to the DelphesPythia8Reader to make jet matching also work with Pythia Versions later than 8.3. Use same code as in the equivalent Delphes reader.

ENDRELEASENOTES

[tmadlener]

Is there an easy way to check whether matching works as expected that could be put into a test case?

[bistapf]

Do you mean to check if it's actually running/properly set-up, or also that it gives correct physics?

For the first, can just check if: number reco events < number input LHE events in a test case with matching turned on. Should always be the case if jet matching works correctly I think(note that only for some FCC-hh sample we need to use the matching, so need a dedicated tester job with one of these). And/or could check for this print-out at the end of the run:

 *-------  JetMatching Error and Warning Messages Statistics  -----------------------------------------------------* 
 |                                                                                                                 | 
 |  times   message                                                                                                | 
 |                                                                                                                 | 
 |      0   no errors or warnings to report                                                                        | 
 |                                                                                                                 | 
 *-------  End JetMatching Error and Warning Messages Statistics  -------------------------------------------------* 

Don't know if Pythia has some internal variable it uses for this that we could access/check.

To check also if physics makes sense, could compare the resulting matching efficiency of a test job to whatever this process had in a previous production (this is stored in the FCC database somewhere), but they are derived from very large scale productions so would be a rough comparison since it might vary a little depending which LHE file/seed you're running on.

[tmadlener]

No, really just on the technical level to make sure if a pythia card with matching turned on, we actually get matching running. So checking the output is a solution, but we should make sure that the output was indeed different before this fix (and that the test actually fails before).