From: Djamel Ouerdane (ouerdane@nbi.dk)
Date: Tue Nov 19 2002 - 16:43:28 EST
I like this idea of probability. I started something based on slice fitting (eg : 1/beta vs p, ring rad vs p, etc) where you get the sigmas of the observables. Then if one knows what is a true n sigma cut on these observables, you can start generating probabilities. Djam > Dear Claus, > your scheme seems very resonable. Do you plan to decide > weather a given track is a pion, or a kaon, or a proton? An alternative > is to statistically identify each track and say that it is 85% a pion, > 14% a kaon and 1% a proton. If one cuts in "orthogonal" variables such > as mass**2 and confidence level of the track then the total efficency is > just the product of the indivdual efficencies. These are surely best > evaluated from the fits and often leave some room for interpreation. > This whiggle room ends up in your systematic error. If one does cuts > in variables that are correlated things are a lot harder. > However the efficecies can be evaluated from histogrammes after all > of your loops. > YOurs Michael > > > Quoting "Claus O. E. Jorgensen" <ekman@nbi.dk>: > > > > > Hi analyzer, > > > > After some correspondence on the analysis of the dbsts I have > > now written up some thoughts on how to get on with the analysis > > from the bdsts. The ambition is to end up with some kind of > > standard analysis method in the future. > > As Jens-Ivar pointed out this discussion should be on the dev-list > > and as Flemming pointed out we should (think a bit and) agree > > before we do the coding (thanks for the comments). > > > > What we want to do: > > > > - Select events > > - Select good tracks > > - Identify particles > > - Evaluate efficiencies > > - ??? > > > > I like the way it is done in the Bdst{Mrs,Fs}Ana (the new versions of > > Br{Mrs,Fs}DstAna) modules. The basic idea is to scan the data and > > determine various constants for event selection, momentum > > determination, track selection and pid selection (in the code these > > scans is called the prepreloop and preloop). The found constants are > > then used when selecting events, tracks and identified particles in the > > final loop over all events and tracks. > > > > What are these constants and how are they determined? > > > > Event Selection: > > > > - Difference in bb and zdc vertex (mean and sigma). > > Determined by fitting a simple histogram (bbVtxZ - zdcVtxZ) > > which is filled in the preloop. > > A nSigma cut can then by applied in the "real" loop. > > > > - Vertex range. Set by the user. > > > > - Centrality range. Set by the user. > > > > - Good trigger. > > > > > > Track Selection: > > > > - Track to vertex (meanZ, sigmaZ, meanY, sigmaY) > > Determined by fitting histograms filled in the preloop. > > > > - Good track status. > > > > - Fiducial cuts? > > > > > > Pid Selection: > > > > - Constant determining the expectation curves (for example mass2) > > for each particle for each pid detector. Found by fitting > > histograms filled in the preloop. > > > > - Sigma from expectation curve (momentum dependent). > > > > We can maybe have a method that return the number of sigmas from > > the expectation curve for a given particle specie, or? > > I don't think there's anything wrong in "fine-tuning the > > calibrations" at this point (the alternative is several iterations > > of the calibrations to get the 100% correct values). > > > > Efficiency: > > > > - Pawel is the expert in this and I'll not try to describe it, but > > I think it should be in a separate module. > > > > This stuff described above is actually not so far from what is in > > the code now. Maybe we can split the tasks into several modules, or? > > I would like to try to put the skeleton together, then we can always > > discuss the details...any comments or suggestions? > > > > How can we implement the pp (or d+Au) in such a framework? How do want > > to pass on the information (at this point it's saved in a ntuple which > > adds another step in the analysis chain)? > > > > Cheers, > > > > Claus > > > > +------------------------------------------------------------+ > > | Claus E. Jørgensen | > > | Cand. Scient. Phone : (+45) 33 32 49 49 | > > | Cell : (+45) 27 28 49 49 | > > | Niels Bohr Institute, Ta-2, Office : (+45) 35 32 54 04 | > > | Blegdamsvej 17, DK-2100, E-mail : ekman@nbi.dk | > > | University of Copenhagen Home : www.nbi.dk/~ekman/ | > > +------------------------------------------------------------+ > > > > > > > ------------------------------------------------- > This mail sent through IMP: http://horde.org/imp/ > -- Djamel Ouerdane ------------------------------------------o | Niels Bohr Institute | Home: | | Blegdamsvej 17, DK-2100 Ø | Jagtvej 141 2D, | | Fax: +45 35 32 50 16 | DK-2200 Copenhagen N | | Tel: +45 35 32 52 69 | +45 35 86 19 74 | | http://www.nbi.dk/~ouerdane | | ouerdane@nbi.dk | o---------------------------------------------------------o
This archive was generated by hypermail 2.1.5 : Tue Nov 19 2002 - 16:52:03 EST