Hi folks,
might be that some of you got this message yesterday.
But I only got a lot of system messages that it wasn't
possible to deliver the mail.
Perhaps the mail system is more reliable today.
Franz
---------- Forwarded message ----------
Date: Sun, 10 May 1998 10:49:45 -0400 (EDT)
Minutes of the DC/tracking meeting Tuesday 5/5/98
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present: Mac, Rob, Joe, Liming, Nicolai, Stepan, Franz
Agenda:
1. hit based tracking report -- Franz
2. x vs. t fitting -- Liming
3. t0's for real data -- Mac (for Alex)
4. alignment -- (all)
5. bank structure of tracking -- Franz
item 1:
Franz reported the results of the last meeting's discussion
on possible improvements on hit based tracking.
He started to work on a new procedure for cluster finding and
linking.
item 2:
Concerning the B dependence of the x vs. t function Liming
found the the local angle (alpha) has to be corrected by 3 to 8 nsec
(depending on beta and field strength). The correction seems
to be linear in cos(alpha). This is consistent with Mac's observations
at his former BNL experiment.
The x vs. t function for electrons (defined by beta=1)
is different from that for hadrons (pos./neg. pions, protons).
The function will have the following input parameters:
drift time,
beta,
local angle,
B field;
and the output parameters:
doca,
sigma (sigma is distance dependent).
Up to now SSLT uses a straight line fit for all superlayers.
Nicolai pointed out that a linear function is not sufficient
in region 2 superlayers because of deflections in the magn. field.
It would be better to use a helix function (taking the hbt momentum
as constraint).
item 3:
Alex. studied the drift time spectra for (almost) all single wires.
In Sector 6 Region 1 there are groups of wires (belonging to 3 cables)
showing offsets of 10-15 nsec for t0 compared with neighbouring
channels. Shifts of some other channels (wires within one layer)
may match to disconnected field wires resulting in a reduced electric
field. Further investigations are neccessary in order to adjust the t0
for all those channels where the pulser calibration wasn't successful.
item 4:
cf. calcom meeting (5/1/98).
Nicolai's alignment corrections will be checked via a chi^2 test
with his numbers on nominal geometry setting, and Nicolai will
rerun his fitting routines with the updated geometry.
A comparison with Rob's alignment fitting will only be possible
when the studies will be based on the same geometry setting.
item 5:
postponed (lunch time ;-)
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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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