<div dir="ltr"><div><div><div><div><br></div></div></div></div><br><div class="gmail_quote">---------- Forwarded message ----------<br>From: <b class="gmail_sendername">Ewa Rondio</b> <<a href="mailto:Ewa.Rondio@fuw.edu.pl">Ewa.Rondio@fuw.edu.pl</a>><br>
Date: Sun, Jun 9, 2013 at 12:00 PM<br>Subject: comments/questions to PR12-13-011<br>To: <a href="mailto:slifer@jlab.org">slifer@jlab.org</a><br>Cc: Naomi Makins <<a href="mailto:gnome@jlab.org">gnome@jlab.org</a>>, Juergen Arends <<a href="mailto:arends@kph.uni-mainz.de">arends@kph.uni-mainz.de</a>><br>
<br><br>Dear Karl,<br>
<br>
Thank you for well written proposal. I like the summary of theoretical approaches.<br>
Below is the list of comments/questions from the first reading, part could be obvious for<br>
You, but not clear for the PAC members not working at JLab.<br>
If You need any clarifications, please lat me know.<br>
<br>
best regards<br>
<br>
Ewa Rondio<br>
<br>
The measurement is very sensitive to the systematic effects and good control of them is the<br>
key point. Therefor I would like to know if there are any estimates of expected size of effects from:<br>
1. beam - one aspect is the stability in terms of position and divergency<br>
this can change acceptance and produce false asymmetries<br>
2 beam polarization - how the unpolarized beam will be obtained what kind of effects are<br>
expected from beam polarization (ie. to which level exact averaging of opposite beam polarity<br>
is needed and how the phase space of the beam is polarization dependent)<br>
3. temperature effects on the efficiency (and stability of the detectors allignment) - proposed scheme<br>
of polarization reversals will give data with target polarization during the day and unpolarized<br>
at night or vice versa. This can introduce false asymmetry related to any kind of temperature<br>
dependence in efficiency or allignment. Was it estimated ? Are there any studies of this kind of effects<br>
in previous experiments?<br>
4. for the drift of efficiency and its time dependence (page 25) linear evolution in time is assumed.<br>
for which effects it is justified? It is clear that for example changes in packing factor of dilution factor<br>
can have "step like" characteristics. Are there any ideas to what level such effects can be controlled<br>
during the run?<br>
<br>
In the proposal "consistency checks on measured cross section for each run" is mentioned.<br>
What precisely is meant? At what level it can be done for the proposed measurement? Please give<br>
more detail, especially on the precision of such test.<br>
<br>
The other test mentioned in the proposal, where I would like to have some more comments on is "the<br>
measurements of dilution and packing factor - with carbon target "- what exactly is planed and which<br>
precision can be obtained? is it included in the beam time estimate?<br>
<br>
It would be interesting to see comparison of expected statistical errors in each bin with expected false<br>
asymmetries from time variation of beam and efficiency/acceptance.<br>
<br>
What are the arguments for proposed binning in x?<br>
the last bean is clear, as much data in this configuration as possible, but splitting of SHMS data taking<br>
in 3 intervals is not discussed from the optimalization point of view, it would be good to have it in the<br>
presentation.<br>
<br>
In general, also the authors call the measurement "ratio method" it is the cross section difference method<br>
as the two data sets are taken at different time. Advantage of "ratio method" can be fully used when two<br>
target cels are exposed at the same time and next order is reversed. Such configuration allows several<br>
additional cross checks, but requires two cell target.<br>
<br>
test of Close-Kumano sum rule - it is very hard to do such test with limited coverage in x, may be some<br>
estimates of contribution measured/extrapolated can be done for specific models. For the models mentioned<br>
on page 17 - can one get some idea what would be the contribution in measured range?<br>
</div><br></div>