I am rather busy with the run, but I really think that to make progress
we should really look at the distribution of events around a wire, both
in time and in space and check for basic things in the chamber. If I may
suggest
- The time spectrum and hit distribution should be L/R symmetric
- xdrift corresponds to a cell lenght
- given 3 hits in a stub you can use two to determine the position of the 3rd
- We should also compare x_drift over each cell since we know
the regions of inefficiency there and also the stagger of the middle
wire. Such a distribution along a plane should also have no overlaps
across cells and an overall smooth behaviour (rate angular dependence)
There is probably a lot more. I understand the t0, x0 offsets are not
final but that affects only the interpretation of such an analysis. And it
would really be important to see the results for the present wch data.
P.S.
I don't know what sigma_z means below. Is it the difference L and R ?
and I doubt sigma_e is 0.05 GeV ...
-- ________________________________________________________________________________ Tancredi Botto, phone: +1-617-253-9204 mobile: +1-978-490-4124 research scientist MIT/Bates, 21 Manning Av Middleton MA, 01949 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^On Fri, 2 May 2003, Chris Crawford wrote:
> hi, > the analysis has finished for runs 3063-3105. unfortunately, there is > no substantial improvement in resolution after the bugfix. > before after (sigma) > p .05592 .0564 GeV > th .09207 .9118 deg > phi 1.112 1.103 deg > z 2.179 2.172 cm > --chris > > Chris Crawford wrote: > > > hi, > > i checked in the fixes to v2, and also b2_17 and b2_18 bugfix > > branches. i am currently making new ntuples for runs 3063-3109 with > > the fixed version 2_18 to test the improvement in resolution. > > --chris > > > > Douglas Hasell wrote: > > > >> Hi, > >> > >> Aaron has pointed out an error in the time to position algorithm. > >> > >> In order to simplify the algorithm I parameterized the time to > >> position relationship for super-layer=0 and then used symmetry > >> arguments to use the same parameterization for super-layer=1. > >> However, I forgot to flip one symmetry axis. > >> > >> So, somewhere in the code (Tong took the code I sent him and > >> changed it to conform to whatever conventions you are using) there > >> should be something like this: > >> > >> float WC_pos_vs_t( int wire, int super, float theta, float bfield, > >> int pm, > >> float t ) { > >> > >> ... > >> ... > >> ... > >> > >> // If this is superlayer 1 reverse the wire number and field. > >> > >> if( super == 1 ) { > >> wire = 2 - wire; > >> bfield = - bfield; > >> } > >> > >> The above lines (or equivalent after Tong changed things) > >> should also reverse the track angle and look something like this: > >> > >> // If this is superlayer 1 reverse the wire number, track angle and > >> field. > >> > >> if( super == 1 ) { > >> wire = 2 - wire; > >> theta = -theta > >> bfield = -bfield; > >> } > >> > >> Could someone please change this in the appropriate place > >> since Tong is away and let everyone know when it is changed? Thanks. > >> > >> Also, Chris, its probably worthwhile redoing the ep analysis > >> as this will change things. > >> > >> Cheers, > >> Douglas > >> > >> 26-415 M.I.T. Tel: +1 617 258 7199 > >> 77 Massachusetts Avenue Fax: +1 617 258 5440 > >> Cambridge, MA 02139, USA E-mail: hasell@mit.edu > > > > > > > >
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