Minutes of the E89044 group meeting, July 21, 1999, at Jefferson Lab
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List of participants:
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Konrad Aniol
Zhengwei Chai
George Chang
Salvatore Frullani
Shalev Gilad
Sabine Jeschonnek
Jim Kelly
Michael Kuss
John LeRose
Richard Lindgren
Dimitri Margaziotis
Charles Perdrisat
Vina Punjabi
Marat Rvachev
Arun Saha
Adam Sarty
Jeffrey Templon
Luminita Todor
Larry Weinstein
- Adam Sarty and Jeff Templon ...
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... spoke about the gory details in unfolding the radiative tail.
The talk was identical (as requested) to the one given in the June 25, 1999 JLab User Group Workshop.
Please check the transparancies of Adams and Jeffs talks and their preprint
nucl-ex/9906008
for detailed information.
Main messages were that going to high Emiss one has to be careful which other kinematical regions may radiate into the region of interest,
and eventually also span those region to be able to unfold the effects.
Also, the standard two-dimensional unfolding seems not to work all the time, and one may have to go up to 5 or 6 dimensions.
Jeff pointed out that not the data have to be "corrected" but the theory has to contain radiative effects.
Alternatively, one can take the theory and radiate it till the result fits the experimental data.
- George Chang ...
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... presented GEANT simulations for collimator punch-through for extended targets.
The studies are motivated by the fact that punch-through may pollute the higher Emiss region with additional counts.
He showed that the electrons deposit almost all their energy and thus don't cause problems.
However, protons loose less energy and moreover, just grazing the collimator, may fill the entire range between the nominal energy and the maximum energy loss.
He also showed simulations that showed that those events may be identified by using selected cuts.
Transparancies will follow.
- Luminita Todor ...
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... demonstrated for the E93050 (VCS) experiment that those cuts to reduce the background from punch-through really work.
She favors two-dimensional cuts which were able to reduce the background dramatically.
Transparancies will follow.
- Nilanga Liyanage ...
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... presented the run plan for optics studies at 4 GeV.
He pointed out that it is uncertain when to run because it needs 4.8 GeV beam energy.
However, the optics should not to be too different from at 3.5 GeV, so the current matrizes are good for online analysis and it is an option to perform the studies even during or after the experiment.
Arun showed that one possible slot is February 2000 when we are running at 4.75 GeV.
Eventually the spectrometer constant may be different, which will show up in shifted missing mass peaks.
- Konrad Aniol ...
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... spoke about luminosity monitoring.
A discussion on this topic you can find here and
there.
- Discussion:
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- UMass sent in a proposal to built a luminosity monitor.
In general, there were doubts that this monitor can even reach a precision of 5%.
The main objection is that it is a non-magnetic single arm detector sensitive to all kinds of background.
- Grenoble sent an email.
They reported that they optimize the kinematics for better Emiss and pmiss acceptances.
In the discussion it was pointed out in doing this one has to take care of the omega-q matching for LT separation too.
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We discussed the uncertainty of the 3He elastic cross section at q2 even as low as 1 (GeV/c)2.
Bill Bertozzi proposed to put a small impurity of 4He into the 3He.
The idea is to use the better known 4He elastic cross section for normalization purposes.
Also, 4He has one form factor only, thus measuring it at one point would link every other measurement at any other angle to it (relative measurement).
Concern was expressed if it is a good idea to contaminate the 3He on purpose.
Eventually, one can think of a second tank with a smaller amount of 3He, mixed with 4He.
- The next E89044 meeting will be held in the week September 13-17.