Close Pair Rejection for Femto

[lauraser]

The class is performing the close pair rejection check for particle pairs.

[jgrosseo]

Hi Laura.
Is this your own implementation because what I had in PairCuts.h is not sufficient? What was missing and can we provide a generic solution also for other analyzers?

[lauraser]

Dear Jan,

the main differences are that:

• in our case, the decision is made by comparing the average dphi, not the min dphi,
• we have our own choice of the array of radii for which we calculate the phi,
• for debugging we will use the 2D histograms created for every radii (which is a hardcoded array mentioned in the second bullet point).

We cannot confirm that this will be as well our final solution for Run3 as we have to test if the same approach works on real data. However, we must validate our codes by comparing AliPhysics results with our new implementation in O2, and thus we need exact replica of the tasks we currently have in AliPhysics.

[lauraser]

Our implementation as well deals separately with different candidates. For example, if the function is called for track and V0 candidates, it loops over V0 daughters and compares the track with both daughters.

[jgrosseo]

Thanks @lauraser
I only have few comments, see above. @mario-krueger will comment on the histogram registry lines and this is only a minor change, too. After that we can merge.

[mario-krueger]

hi Laura,
we now have an add() function in the HistogramRegistry that directly returns the histogram pointer (no more need to extract it manually from the HistType variant via std::get):

histdetadpi[0][0] = mHistogramRegistry->add<TH2>(...)

(see for instance here: https://github.com/AliceO2Group/O2Physics/blob/master/PWGLF/Tasks/spectraTPC.cxx#L71)
Cheers,
Mario