Present: Mac, Liming, John, Alex, Franz
Agenda:
- x(t) parametrization -- Liming
- T0 from drift time spectra -- Liming
- scheme for automatic calibr. procedure -- (all)
item 1:
Proposal for the xvst tables:
Region 1: 10(layers) X 2(local angles) X 200(dtime)
Region 2: 12(layers) X 2(local angles) X 400(dtime) X 10(bfield)
Region 3: 12(layers) X 2(local angles) X 800(dtime)
In order to describe the dependence on local angle values
for alpha=0,30 are stored and then interpolated.
The drift time stamps are 2nsec.
For time walk correction (at short drift times)
the drift time (bins=1nsec) for different beta values are stored.
item 2:
In order to analyze T0 the differential of the drift time spectrum
is used. The t_zero (as turning point in the slope) is
at about 70-80 nsec after overall corrections (tdc/2-t0) (HBT),
at 8-10 nsec after correction for start time and flight time (TBT).
The sigma for t_zero is about 7-10 nsec dep. on beta.
Due to the time and beta corrections the doca residuals in TBT
are strongly dep. on the quality of the part. ident. but
less on beta.
These studies have to be confirmed using different data settings.
item 3:
It's not convenient to re-calibrate the XvsT function for every
run but the values for T_max have to be updated if T_max varies
more than 1%,
whereas the XvsT function should be refitted only if T_max varies
more than 5%.
(roughly: diff.T_max(Reg.1,2) > 5-7nsec; diff.T_max(Reg.3) > 10-12nsec)
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Franz J. Klein, Thomas Jefferson National Accelerator Facility,
12000 Jefferson Avenue MS 12H, Newport News, VA 23606
Email: fklein@jlab.org, Tel: (757)269-5879, Fax: (757)269-5800
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