now that CEBAF Internet connections have risen from the dead,
I feel it's a good idea to check out our new distribution list
and at the same time begin a conversation about our upcoming
meeting during the CLAS collaboration meeting. I have taken the
liberty to add a couple more names to the list, so if you DO get
this message, you are on it; however, if you know somebody who
didn't, tell them to subscribe. Please send replies of GENERAL
interest to "eg1_run@cebaf.gov" - then all of us can read them.
If you have a message specifically for ME, DON'T use that address
(or the "REPLY" button) but send it directly to "kuhn@jlab.org"
The official CLAS collaboration meeting agenda
shows us (=EG1) meeting on Friday, 9/5, at 450-600pm in room L109.
We definitely need to make use of that time (and maybe hang on a
little bit longer). We need to discuss progress towards running
and the run plan itself. I list a few relevant topics below;
however, I am asking all of you to add to this list and/or
let me know if you want to make a presentation at the meeting.
Don Crabb will also give a talk on the polarized target (status) on
Saturday morning at 9:00. There also will be a discussion
of the runplan on Saturday (we surely can expect some tough questions
from the collaboration, now that eg1 has appeared on the official
Jefferson Lab schedule). Also, our beam request is due on the
following Tuesday, 9/9, so we need to have it ready.
To prepare for our meeting, let me list some important things that
need sorting out soon for us to stay on track for a 1998 run:
1) Beam time request (see above): We don't HAVE to submit a completely
new request, since they have already the one on file that I submitted
in spring. However, we will have to update what has changed, and maybe
supply whatever additional details we have. I'll bring a draft to the
meeting on 9/5.
2) Beam energies: We requested equal time for the four "standard"
beam energies from 1.6 through 4 GeV. This will have to be updated in
light of the fact that we need to run at energies compatible with Gen
in Hall C. From my understanding of Charlie Sinclair's note, we could
run at 2.376 GeV and at 1.592 GeV (close enough to our lower energy
points) which would allow Hall C to run at 3.930 and 3.914 GeV,
respectively (this is very close to their preferred high energy
setting of 3.97 GeV). In addition, we could also run at 3.534 GeV
(halfway between our 2 high energy points) while they run at 2.835 GeV
(their second data point is nominally at 2.85 GeV). Finally, we
could also run at the "magic" energy of 4.23 GeV, which would allow
Hall A to make use of the polarized beam also.
3) Target design: We need to freeze design questions like the dimensions
of the target cells, which targets we are going to use (I plead for
NH3, ND3 and CO2 or solid carbon) and the geometry of HF and NMR
coils. For the latter, we need to decide whether to put them inside
the target material or around it. My personal opinion is that we can
live with the coils outside the target material. This will make it much
harder to come up with an absolute number for the target polarization,
but might be enough to monitor and optimize during the run. For the
absolute polarization, we can rely on (quasi-)elastic inclusive
scattering (e,e') and the known values for the elastic form factors
of the nucleons (protons dominate). I have looked at this once again
and am convinced that we can determine the product of target and
beam polarization to an accuracy of better than 1% (statistical)
within 10 days of running (i.e., to 3.3% within 1 day, which is
already better than NMR plus Moeller can hope to achieve). Possible
systematic errors are not trivial, but we have the added benefit that
some of them will cancel with corresponding errors in the determination
of g1 (e.g., dilution factor uncertainties from exact target compo-
sition).
3) Moeller: I believe that Duke University has made an agreement with
the Florida International University group to help with the
Moeller polarimeter. I hope we will hear more about that at the meeting.
Please give me your input (and ideas for the agenda on 9/5).
Many greetings -
--
- Sebastian
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Phone: (757) 683-5804
FAX: (757) 683-5809
Email: kuhn@jlab.org
WWW: http://macsek.physics.odu.edu/
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