Optimise charm neutral lines
Charm neutral lines (three-body with pi0 and radiative decays) take up a significant fraction of the bandwidth, but are still missing the information to apply an improved ECAL calibration or gamma/pi0 reconstruction offline. This MR tries to improve things by:
- adding a DOCA < 100(150) um requirement for decays into two (three) tracks. This is checked to reduce the rate by 10% on D0 -> hhgamma
- persisting the ECAL information for neutral candidates (possibly including isolation particles). This increases the bandwidth by around 30% in D0 -> hhgamma
- selecting only K- pi+ pairs within 120 MeV from the K*(892) mass for the D0 -> K- pi+ gamma line (reduces the rate by around 50%)
For context, the bandwidths of the relevant modules before this MR were:
-
d0_to_hhgamma.py-> ~250 MB/s -
d0_to_hhpi0.py-> ~180 MB/s -
d_to_hhhgamma.py-> ~35 MB/s
Possible changes in case the rate needs to be reduced further:
- what is the use of saving all particles in a cone? For tracks of charged particles, are you interested in rejecting D decays with additional tracks? Then you could save only tracks compatible with coming from the D decay vertex, which should reduce the bandwidth a lot. Is the value of the cone aperture for the neutral particles tuned to the analysis requirements?
- add a prescale for D0 -> K- pi+ pi0 if needed to remove the bandwidth? The BR is larger than D0 -> pi+ pi- pi0 by around a factor of 10.