Draft: B&Q: optimize prompt D0 anti-D0 B&Q double charm lines (and consistency with samesign/oppositesign B&Q lines)

[the description is still incomplete and a work in progress]

optimize prompt D0 anti-D0 B&Q double charm lines (and consistency with samesign/oppositesign B&Q lines)

The idea is to maximise our signal throughput for the 2024 End-of-year Resprucing (B&Q deadline 20 October, final deadline 29 October).

This MR targets !3839 and depends on !3878 (merge imminent).

Some issues with some/all of these lines were discussed in #840

• Steps were taken to reduce HLT2 rate for these lines in !3883 (merged)
• !3870 (merged) also helped

Analysis Productions in progress: lhcb-datapkg/AnalysisProductions!1771

Things left to understand:

• Where are we now, in the landscape of HLT2 rate and Sprucing rate?
• We have sprucing lines which run on the FULL stream output of HLT2. Several additional selections have been placed to reduce the rate of our lines in HLT2 and also separately in the Sprucing.
  • We need to see if any of these cuts has an adverse effect on our future plans (vertex fit chi2 cut in HLT2 of pressing concern)
• Since we go to FULL stream, persistreco=True doesn't really have meaning (or does it?)
• Is it OK to remain in FULL/persistreco=True or do we need to or should we move to selective persistence
  • if we did, we would still want any kaon/pion/photon from the PV for possibly full reco of DDbarpi0/gamma and investigation of (cone) isolation variables which may have some use in busy events

Desireables:

• remove or raise prescales in HLT2 and/or Sprucing
• make sure we have whatever we need to investigate isolation variables
• would be nice to be able to calculate efficiencies from single charm potentially