Hi Flemming and Ian, I think that the calibration of T2 using T3 is Ok and we can trust it. Concerning T1 calibration: we use combined T2 - T3 tracks, so first we match T2 and T3 track to make sure they come from the same particle and the then we replace y-slope of the T2 tracks by y-slope of the T3 track and swim it back to T1. This means that we use y position from T2 and y-slope from T3 and it works fine giving the errors of 0.5% on the deduced drift velocity in T1 (In T2 we have 0.1% error). Of course, in this method we have to base on the correctness of T3 y-slopes. I've made some analysis to check that, by looking at the T3 and T4 correlation. To see this analysis please, go to http://www.nbi.dk/~staszel/fs/detectors/tpc/ Regards Pawel. > > > Second comment: > > I will like to have some discussion on the Vdrift calibration on T2(T1). I > > have seen the plots from > > Pawel that shows a small difference between the Y(T2) and > > projected Y(T3) to > > T2 in the order of 0.01 in Vdrift. > > It is not priory obvious what is the better value being sensitive to > > slightly different effects (the projections to the > > fibers depends on the . One should though keep in mind that projecting to > > in particular T1 is a long projection over 6 meters - > > this couls be checked by looking at the T3 projection to the fiberplane(s) > > and getting the local Y for the T3 tracks that has > > signals in the fibers just as for the T1,T2 local tracks. > > Certainly one lesson from the Tpm2 vdrift from the fibers was the > > front/back > > gave different values. > It is a good idea to check the T3 tracks directly against the fibers. As > far as I know this has not (yet) been done. Pawel has checked T3 vs T4 and > T5 to get an idea how confident we can be in the T3 projections, and I am > sure he will soon share these results with all of us. > It seems to me that the T3->T2 is OK, and for runs where the vdrift has been > found using both T3 and fibers the results are consistent. The reason for > developing the T3 method is that it can be used for the entire run, whereas > the fibers can not. > It is true that there are uncertainties associated with projecting T3 tracks > to T1, and this is being taken into consideration. > Finally, it should be noted that the point of this work is to more densely > populate the data base, and it is done more quickly using T3. > It should also be pointed out that the US beat Portugal (3-2) this morming > in an absolutely beautiful football match! > Cheers, > Ian > > -- ---------------------------------------------------------------------- | Pawel Staszel | | Niels Bohr Institute Tb 8 email: staszel@nbi.dk | | Blegdamsvej 17 phone: (+45) 35 32 53 51 | | København Ø FAX: (+45) 35 32 50 16 | | Danmark | ----------------------------------------------------------------------
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