Hi,
I made a class TBLDetFitEL to fit some of the field off data taken
during the last few months. I guess this would be my topic on the analysis
meeting but since I changed BlastLib once again, I want to keep everyone
updated.
I did some work on runs 2723-2727 which as I know were with field off.
(Arron and I took them). Few interesting things:
1st: Tong discovered from graphically display WC data that a lot of tracks
came from down stream. my ananlysis confirmed it. I recover a lot of
events that can be fitted into a elastic scattering from Z0>22cm, i.e.,
off stream. a lot of them gather at Z0=30-40cm.
They can be fitted to a hadron side mass of 4-5 GeV. the fitted hadron
mass spectra display peaks at this region, a cut of Z0<22cm get rid of
them with almost no residual.
They display a huge left right aymmetry, Sum(electron sector
number)/number of events = 0.32, beam is scrapping something on one side?
2nd: The fitted hadron mass spectra has a peak at M=0.45GeV. A cut of
hadron side average tdc - electron average tdc > 5 nanosec, get right of
this peak with almost no residual.
So these events correspond to 'fast fast' coincidence I guess.
They display a huge left right asymmetry too. Sum(electron sector
number)/number of events = 0.70, more right sector than the left.
3rd: a cut of:
-22<Z0<22, (phi_e-phi_p)^2<0.1, average proton tdc - average
electron tdc > 5 nano second, left me with proton mass of
1.2+-0.4.
there is only 1% left right asymmetry in these events:
Sum(electron sector number)/number of events = 0.506.
I am afraid this is the best resolution I can get from scintillator
signals. there are 1-2 deg out of 20 deg in electron angle, a few degrees
out of 70-80 deg on proton side. Z0 resolution is 6-7 cm.
4th: sum up the numbers:
run 2723-2727 contains: 530917 physics events, 477241 of them I would call
clean events in the sense that one tof on each sector fired, one or zero
CC on each sector fired.
39117 of them can be fit into a elastic scattering model. The fit is done
in the following way. if I assume the one with smaller tdc is electron,
assum the particles hit the center of TOF scintillators in X and Z
directions(see blast.geom), with y calculated from tdc position times
50pecosec/channel and 0.0147cm/pecosec. I can then for any position Z0
along target cell a theta_e, and a theta_p. Then theta_p2 can be
calculated from theta_e. vary Z0 to find a point where theta_p calculated
from theta_e is equal to theta_p calculated from geometry.
among them:
30905 are close to coplain: (phi_e - phi_p)^2<0.1 rad^2. (pretty loose)
among these 30905:
I can fit 11393 to target region: -22<Z0<22; a big loss.
among these 11393:
8867 of them survived the cut: average proton tdc-average electron tdc>5
nano sec
among these 8850 have: theta_e< 30 degrees
To the end, I exhausted my wisdom on inventing new cuts. The resulting
proton mass reconstruction is: 1.2+-0.4 GeV.
The plan is to go on to field on case. But I am not sure how to do it
yet.
If you are interested in this stuff, please see my directory:
spud?:~blast/commis/phase1/ANALYSIS/CHI/TestFit.C and DetFit.root
and the source code in BlastLib2.
The codes are checked into CVS, tagged v2_8.
Again, they are not tested with any online analysis code since test the
code one macro and another would take a whole day. no copy is made in
lib/spud.
I think I found the problem that crippled ntuple.C on Monday. It was a
broken dependence between TBLCut_coda and TBLDetRecon. I think it is a bad
idea to keep these two classes together. I added book keeping functions
into TBLDetRecon so TBLCut_coda shall become obsolete. However, I did not
change TBLCut_coda and the file structure of BlastLib2 anyway.
If you want to compile the library for spuds, first revert to earlier
versions with:
cvs up -rv2_3 or 4 or 5
Chi
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