Weekly meeting minutes - September 30, 2005
Present: M. Wood, M. Ito, E. Clinton, V. Mochalov,
Y. Prok, K. Hardy, D. McNulty, L. Benton,
A. Teymurazyan
On the phone: L. Gan, R. Miskimen, A. Bernstein
Secretary: Yelena Prok ( Mike Wood will be next secretary)
1. Review of last meeting minutes:
Discussed the recent developments in tagger calibrations by Dave
Lawrence. Dave has produced new calibration constants which align tagger
timing signal with respect to the timing signals from TAC, PS paddle #5,
or HYCAL total sum (bit 9). Some histograms from this investigation
can be found at
http://www.jlab.org/~davidl/PrimEx/Presentations/2005_09_29_tagger_calib/
In summary, using TAC and PS paddle #5 produce consistent results, with
little variation in time (from run to run), which is not the case when
bit 9 is used as a timing stop. Pair Spectrometer will be used to
produce calibration constants for the production runs.
Dave also volunteered to create a new bank which would hold a list of
photon candidates for the event, based on the time difference between
tagger time and HYCAL total sum.
2. Status of HYCAL reconstruction
Vasily Mochalov discussed the status of HYCAL reconstruction which is
very nicely summarized in
http://www.jlab.org/~mochalov/hycal_software/primex_meetings/2005-September-30.html
Some important highlights of this discussion:
1. What to do about the changing sparcification cuts during the run?
2. Knowledge of the distance from HYCAL to the target cannot be
extracted from the physics processes, as it becomes very sensitive
to the gain constants. NEED TO FIX THE DISTANCE BEFORE ENERGY
CALIBRATIONS USING PHYSICS PROCESSES CAN PROCEED.
3. Also important to know the beam position on HYCAL. Who will
analyze the L. Gan's photon beam profiler data to extract the
actual beam coordinates?
3. Veto Analysis of pi0 Events from Pb Target
Mike Wood showed some invariant mass distributions from pairs of
clusters using Pb target runs (no cuts of any kind were made, z=730 cm).
The slides can be accessed from the weekly meeting page,
/group/primex/html/weekly_meetings/slides_2005_09_30/mhw_30sep2005/
There are 4 distributions on each histogram:
black: no VETO cut
red: both clusters neutral
green: both clusters charged
blue: one charged, one neutral
There is a large peak at ~200 MeV, in the case of both clusters
being charged. Also, events with more than 3 clusters do not show
any significant enhancement around pi0 mass.
4. Some organizational issues:
1. Not everyone has been able to join the meetings by phone. If
someone would like to change the time of the meeting, please let
Mark Ito know by email.
2. Any thoughts on the time of the next collaboration meeting?