BT Meeting minutes
I did not take detailed minutes as I normally do, just had time to write some comments that I think are worth keeping to the records
- Event selection cuts:
- Bill warns that the vertex selection should not be used blindly, in particular if we are in sync with the latest GR versions wehere we added the neutral energy events variables, which effectively doubles the number of vertices. His suggestion is to look at the vertex status bits and verify that the cuts we use do what we think
- Simulation status
- Luca suggest to change benchmark run for producing different MC flavors, and move away from 2082 which was shown to have some possible issue in the beam phase space plots
- Collimator simulation
- Bill commented that an actual collimator is much heavier than what was simulated and shown by Johan; he requested a thorough check of the beam line simulation
- Francesco will provide documentation on the current simulation which indeed includes all the material along the beamline, but does not simulate the actual beamline in its full length; we will consider such a simulation
- electron/hadron separation
- Francesco presented a study to separate these two classes of events based on max likelihood method
- Alex requested details for the calculation of the likelihood as he thinks the method is not applicable since you have to know particle energies a priori
- Francesco and Nicola clarified that the purpose of the study is to make a data-MC agreement study, not to identify electrons in flight
- 2082 beam spot issue
- Nicola suggest it is due to a weird combination of noise strips in layers 31 and 35
- Leon thinks we should keep that in mind as we treat noisy strips with different thresholds in DAQ and in offline reconstruction software
Simulation Status
- Pass5 variables in BTRelease tag v7r1215p0, in sync GR v12r15, with following exceptions:
- G4Generator v5r19p0 and G4HadronSim v1r2p0, Ion Physics for QGSP_BERT
- BR continues to use AcdUtil v1r4p1, AcdDigi v1r20, and AcdRecon v3r7p2 (tags of GR v11r17), because with newer tags the code terminates in AcdUtil::AcdTileDim().
- xmlGeoDbs v1r47p1, air instead of the virtual calorimeter in bay 0
- In the release manager, all compiles, and several test programs (more than usual) core dump. Probably incompatibility of the older AcdXxx and the new xmlGeoDbs tag due to changed ACD tile geometry, for the LAT model! However, BR seems to run. ldf2digi and readigi_runrecon on one PS (700001460) and one SPS (700002082) run reproduced previous root files. But still, use with care!
- New simulations for special configuration of run 2082
- with beam energy increased by average discrepancy for run 2082: svac , merit (some cal distributions, Energy and TransRms, Energy per Layer, Energy profile)
- with the Bari digit that simulated charge sharing: svac , merit
- with improved Beam Spot (correct VtxYDir) : svac , merit
- Dead strips are in MC, see for example run 2082 in Tower 2 that has a large dead area on plane 31
- at the RECON level : layer 31 strip chart
- at the DIGI level : Tower 2 plane 31 digi strip chart
- SPS veto counter simulation bug:
Meeting with Bill, Steve, Aous, Riccardo, Eric C, Philippe, Luca, Johan, Leon, Robert Johnson during the collaboration meeting to discuss BT and background rejection
- Effects of BT discrepancies on background rejection:
- Michael et al working on a new release to include pass5 variables into BTRelease; fixing some issues with tagger variables as well; now working on issues from synchornization with GR
- the plan is to check CTBTKR/CAL/GamProbs in the CU and go back to more raw variables in case of differences; prefilter cuts should be first checked; CTBCPFGamProb is not applicable to CU geometry given the few ACD tiles available
- Riccardo is documenting prefilter cuts and relative variable importance for pass5 and will maintain a page for further passes - work in progress
- several people expressed interest for studying a specific subsystem set of variables, which will eventually help shaping a core team of background rejection analyst - more are welcome
- open discussion on which tool should be used to deal with classification analysis (IM, RForest, orange, ROOT); Bill strongly suggest IM, at least for a softer learning curve and easier comparison with his analysis
Some suggestions from Bill and Steve discussed yesterday
- Background rejection variables
- Bill looked at runs 2082 (20GeV e, 0 deg) and 1445 (full-brem gammas) and ran his CT analysis for data and MC; preliminary indications give a small effect on CTBTKRGamProb, a 7% difference on CTBCALGamProb but a negligible effect on the final event classification, i.e. CTBClassLevel; this is encouraging
- Tkr variables
- Bill wants to independetly double-check the beam cleanliness by hand-scanning some events; we discussed on the possibility of providing such a sample set of events along with systemtest or through the pipeline (Tony should be able to run WIRED on the web from user requests on specific runs and number of events)
- Energy scale discrepancy
- Bill is reassured by the Geant4-EGS5 comparison, he believe we have a miscalibration somewhere, either in the beamline settings or in the CAL calibration
- Steve is looking into the CAL calibration procedure with help from Sasha and Philippe
- Bill requested an evaluation of the overall uncertainty on the absolute CAL calibration from the uncertainties in the various steps of the calibration
- Philippe will finalize his analysis of calibration factors to be used for i) scaling CAL variables in the data-like simulation ii) use them to recalibrate the LAT CAL if needed
BT Meeting, november 7
Unedited notes taken during the meeting, corrections and additions are welcome LL
News
PB: official launch date is end of may, see here
Pressure scan analysis - Philippe
1: I was working on updated runs. i used this scan as a scan in extra x0, not with the aim of determine the correct pressure, which we know from the records. current sim is not exactly what we had at SPS, difference should be negligible anyway
2: 4 scenarios considered in the analysis, increasing complexity
3: scenario 1, one plot per configuration, differences between data and MC for each layer, the fit pressure is written in the plot, 2bar. note that at 0 and 20 deg we have behaviour which decreases with layer, while it is the opposite at 10 and 30 deg (not always obvious, but there is a trend). a negative slope would indicate more material in data wrt MC, a positive slope is the opposite
4: scenarios 1 and 4 (in blue). obviousloy chi-sq is much better, and max discrepancy is about 4% and is quite flat. BUT
5: plotting the pressure for different angles you see a similar structure for different energies (left plot); right plot is more flast vs energy, so somehow there is an indication that scenario 3 (pressure per angle) is favoured wrt scenario 2 (pressure per energy)
6: scenario 3.
7: tkrtotalhits from merit (in fact clusters) horizontal red line is data, blue vertical is best fit result for tkrtotalhit, red vertical is fit result from scenario 3
8: same as 7 but on tkr1corehc; best fit (blue line) is now 0.3bar. note 10 gev, 20 deg, data is always below the scan points, so no hope to find a scale factor and a pressure that minimizes the discrepancy
9: fitting caltransrms, we are in trouble here; adding extra material will not solve caltransrms discrepancy
10: since tkrtotalhits require 1 bar, i looked at cal layer energy in scenario 1 using 1 bar, and you can see we have an un satisfactory situation
11: extra material fit for tkrtotalhits would indicate extra 0.05x0, not crazy, but layer energies would require a pressure (i.e. material) per angle. all best fit results for cal layer energies are compatible with tkr best fit, but there is no coherent solution. still have to to look at 200,280 gev data. and caltransrms is anyway out
NM: in slide 10 there is a problem on layer 3 at 20 and 50 gev at 10 deg, did you check that?
PB: checked that, not an issue with fitting
NM: any problem in data or MC?
PB: done that check, no pb there
NM: 10 deg is still in twr2, like 0 deg. anyway conclusion should be 2 bar for cal layers?
PB: not really, more complicated than that. 5% extra x0 before the CU to get agreement on tkrtotalhits, for the energy you need sometyhing in between the tkr and the cal in a bizarre way, which is dependent on the angle. any grid geometry we can think of?
AC: on slide 1 you state in reality we had 0 bars for E>20GeV, and 1 bar . why are you trying to determine the pressure if you know that?
PB: it was the easiest way to check extra material along beam line, indeed we know the pressure in the cerenkov
BL: i would have expected cms people to know well what is in the beam line, but they do not seem to be so sure
NM: as you know there are scintillators that you can move in and out of the beam, 0.05x0 is 1 2cm scintillator, so that is reasonable; more than that would be hard to believe
BL: yes, we knew that and did our best to remove whatever crap was along the beamline. we may check now with the beam line coordinator on what extra material was there. also another degree of freedom is the energy absolute value, not guaranteed at the 1-2% level, although the beam energy is reproducible
NM: any beam line logbook available to check history of material along beam line?
PB: used top be available online, i don't know if that is still the case
PB: for each energy and angle we have 3-4 impact points, and I am looking at different pitures right now, we could for instance scan the material between the 2 towers. maybe something between the towers we can hit at 10 and 30 and not at 0 and 20?
BL: maybe a different contribution from direct diode deposition
LSR: whatever it is, at 10 deg there is a factor of 5 in costheta
PB: we do not exactly hit in the same position, so it should not go with 1/costheta if it something we hit at a given angle
AC: how can we hit diode in the center of towers?
PB: i was not speaking about diode hit, i am thinking about material between the 2 trackers
LSR: beam has some dimension, if these were very small they could have an effect
BL: all the effect of beam size and divergenve are included?
PB: yes johan used our best knowledge of that. also i have some finducial cuts
FL: any news from calice people? do they confirm the extra 0.1X0 and where would that be?
PB: apparently this 0.1X0 was the last nb we got from calice
BG: i did not hear from them, the other guy in my lab was aware but did not know exactly the details
Modifying CAL variables for a data-like simulation
LB: started study for selection of HE electrons, and for assessing systematic effects on that case, we put together this machinery for scaling and shift the variables to modify MC simulations so that they reproduce better BT data for some selected electron and hadron runs. the message is that the machinery is in place
LL: discussed this idea many times, this is a first attempt, we will discuss this in our F2F meeting at NRL
PB: had this discussion several times before. there are some things we can change, the best would be to change something in the simulation and get agreement. i would prefer to do that at the digi or recon level so that all final variables are automatically changed. for other, like caltransrms, we will have to change at the tuple level. the problem for me is that we should not forget about a lot of vars we just started to look at
Had to leave the meeting after this discussion LL