[b1_ana] Fwd: comments/questions to PR12-13-011

[Karl Slifer]

---------- Forwarded message ----------
From: Ewa Rondio <Ewa.Rondio at fuw.edu.pl>
Date: Sun, Jun 9, 2013 at 12:00 PM
Subject: comments/questions to PR12-13-011
To: slifer at jlab.org
Cc: Naomi Makins <gnome at jlab.org>, Juergen Arends <arends at kph.uni-mainz.de>


Dear Karl,

    Thank you for well written proposal. I like the summary of theoretical
approaches.
Below is the list of comments/questions from the first reading, part could
be obvious for
You, but not clear for the PAC members not working at JLab.
If You need any clarifications, please lat me know.

             best regards

                Ewa Rondio

The measurement is very sensitive to the systematic effects and good
control of them is the
key point. Therefor I would like to know if there are any estimates of
expected size of effects from:
1. beam - one aspect is the stability in terms of position and divergency
     this can change acceptance and produce false asymmetries
2 beam polarization - how the unpolarized beam will be obtained what kind
of effects are
     expected from beam polarization (ie. to which level exact averaging of
opposite beam polarity
     is needed and how the phase space of the beam is polarization
dependent)
3. temperature effects on the efficiency (and stability of the detectors
allignment) - proposed scheme
     of polarization reversals will give data with target polarization
during the day and unpolarized
     at night or vice versa. This can introduce false asymmetry related to
any kind of temperature
     dependence in efficiency or allignment. Was it estimated ? Are there
any studies of this kind of effects
     in previous experiments?
4. for  the drift of efficiency and its time dependence (page 25) linear
evolution in time is assumed.
     for which effects it is justified? It is clear that for example
changes in packing factor of dilution factor
     can have "step like" characteristics. Are there any ideas to what
level such effects can be controlled
     during the run?

In the proposal  "consistency checks on measured cross section for each
run" is mentioned.
 What precisely is meant? At what level it can be done for the proposed
measurement? Please give
 more detail, especially on the precision of such test.

The other test mentioned in the proposal, where I would like to have some
more comments on is "the
measurements of dilution and packing factor - with carbon target "- what
exactly is planed and which
precision can be obtained? is it included in the beam time estimate?

It would be interesting to see comparison of expected statistical errors in
each bin with expected false
asymmetries from time variation of beam and efficiency/acceptance.

What are the arguments for proposed binning in x?
the last bean is clear, as much data in this configuration as possible, but
splitting of SHMS data taking
in 3 intervals is not discussed from the optimalization point of view, it
would be good to have it in the
presentation.

In general, also the authors call the measurement "ratio method"  it is the
cross section difference method
as the two data sets are taken at different time. Advantage of "ratio
method" can be fully used when two
target cels are exposed at the same time and next order is reversed. Such
configuration allows several
additional cross checks, but requires two cell target.

test of Close-Kumano sum rule - it is very hard to do such test with
limited coverage in x, may be some
estimates of contribution measured/extrapolated can be done for specific
models. For the models mentioned
on page 17 - can one get some idea what would be the contribution in
measured range?
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