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<div class="moz-cite-prefix">Good afternoon,<br>
<br>
Looking back over the statistics (now with the SMHS limits on
theta and E'), I want to point out that systematics aren't our
only concern. Please see:<br>
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<a
href="https://hallcweb.jlab.org/wiki/index.php/Elong-13-04-29#Maximizing_Rate_.28Minimizing_Azz.29">
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charset=ISO-8859-1">
</a><a
href="https://hallcweb.jlab.org/wiki/index.php/Elong-13-04-29#Maximizing_Rate_.28Minimizing_dAzz.29">https://hallcweb.jlab.org/wiki/index.php/Elong-13-04-29#Maximizing_Rate_.28Minimizing_dAzz.29</a><br>
and<br>
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charset=ISO-8859-1">
<a
href="https://hallcweb.jlab.org/wiki/index.php/Elong-13-04-29#Minimizing_db1">https://hallcweb.jlab.org/wiki/index.php/Elong-13-04-29#Minimizing_db1</a><br>
for what we're able to achieve statistically with one week per
data point. The first plot minimizes dAzz, the second minimizes
F1, which in turn minimizes dB1.<br>
<br>
There are a couple of "sweet spots" in <x> that I'm still in
the process of finding, but for the <x> values we've been
looking at the links above show what we can do.<br>
<br>
Take care,<br>
Ellie<br>
<pre class="moz-signature" cols="72">Elena Long, Ph.D.
Post Doctoral Research Associate
University of New Hampshire
<a class="moz-txt-link-abbreviated" href="mailto:elena.long@unh.edu">elena.long@unh.edu</a>
<a class="moz-txt-link-abbreviated" href="mailto:ellie@jlab.org">ellie@jlab.org</a>
<a class="moz-txt-link-freetext" href="http://nuclear.unh.edu/~elong">http://nuclear.unh.edu/~elong</a>
(603) 862-1962</pre>
On 04/26/2013 02:57 PM, O. A. Rondon wrote:<br>
</div>
<blockquote cite="mid:517ACE2D.3030303@virginia.edu" type="cite">
<pre wrap="">Hi,
As I pointed out in my message about Axx, the Np and Nu have to be
coincidence e'p events for them to be associated to Axx or Azz. And the
coincidence events have to be correlated quasielastic e-p. In such case,
Np, Nu are related to rates from the m=+/-1, 0 states, because only then
Axx is a well defined analyzing power or asymmetry. But it does not work
for DIS, and may not even work for high Q^2 q.e.
If Np, Nu are inclusive events, and we are dealing with ND3,or even LiD,
then we are back, at best, to my method's eq. (19). Feel free to plug in
the detailed expressions and see how things propagate. Keep in mind that
a factor related to the time dependent detector efficiency needs to be
included in all the equations. Such factor is common for the upstream -
downstream difference (data taken simultaneously) but not for the
same-cup one (different periods).
I think one thing that may be ambiguous is what is the emphasis of the
proposal, namely to study a physics quantity by the most accessible
means, or to use the measurement to advance existing techniques, which
is a perfectly valid and worthy goal, but I must say I'm more interested
in the quantity than in the technique.
Cheers,
Oscar
Dustin Keller wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi,
Getting 20% uncertainty using hole burning for negative tensor
polarization down to 5% seems a bit of a stretch to me especially given
the small single people are interested in for b1. But I'm glad to help in
anyway I can to try to get it through.
We really should consider the form of
Azz=(2/Pzz)(N^p-N^u)/N^u
it get the uncertainty from 20% to 10%, a much better starting point.
dustin
On Fri, 26 Apr 2013, Karl Slifer wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi,
While it would be easier to run with only positive Pzz, there is no
technical or theoretical reason that I know of that prevents us from using
negative pol. This will require target development to achieve large
negative as well as positive tensor polarizations, along with careful study
of the systematics in extracting these values. I thought we all agreed on
this yesterday....And I also see no technical or theoretical reason (other
than it is difficult and will require R&D) which limits the enhanced tensor
polarization to 10%. I believe Don, Chris, Josh would all agree with this,
atleast they all did when I talked to them within the last 6 months.
So to be clear, I believe we can propose an experiment where we enhance the
m=0 population (via rf saturation or by using two independent microwave
sources) and measure N_0 unpolarized electrons inclusively scattered while
in this state, and then we deplete the m=0 state to obtain a positive
polarization and measure N_1 unpolarized electrons scattered while in this
state. Then we form the asymmetry (with appropriate numerical factors).
The Pzz will not be the maximal positive or negative value in either state,
but we can correct for this by the relative Pzz in each state. One
significant concern is that this introduces time dependent systematics
since it will likely require some time to switch between the two states.
This has to be studied, but I do not see it as a fundamental limitation.
After careful study of the systematics, its possible that the cross section
difference method may well turn out to be the best way to do the
experiment, but I suspect we will struggle mightily to convince a very
skeptical PAC in 30 mins that we really can control all the systematic
effects to the level needed for a cross section measurement.
With this in mind, I think it is reasonable to aim for conditional approval
based on demonstration of the target performance to the level needed (+-20%
tensor pol with about 5% relative uncertainty). I believe we can defend
these as reasonable goals, although we should get something in the way of a
support statement from Don or Chris. And I believe conditional approval is
a highly desirable state, since the target groups will not be able to
commit serious R&D to this without an approved experiment for motivation.
In addition, it opens the door to attract more theory support and start
consideration of several other possible experiments.
my few further cents,
Karl
---
Karl J. Slifer
Assistant Professor
University of New Hampshire
Telephone : 603-722-0695
On Fri, Apr 26, 2013 at 11:04 AM, Dustin Keller <a class="moz-txt-link-rfc2396E" href="mailto:dustin@jlab.org"><dustin@jlab.org></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">As I mentioned in the meeting using the notation Axx can be
mis-leading especially in the case of DIS where azimuthal
control is not obvious. However the relationship for
sigma^{+/-} for m=+1,-1 is sigma^{+/-}=sigma^u(1+(1/2)AzzPzz).
If you believe that then Axx=Azz, and the conclusion is the same.
If you call it Axx or Azz in either case you just measure the
ratio of polarized and unpolarized cross sections. This will lead
to a target tensor polarization of about 10%. There are certainly
other systematic concerns but this is the best we can do target wise.
dustin
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