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