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<p class="MsoNormal">Dear Ashot,<o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p> You say that you would like others to contribute to this discussion. That is fine with me, I assumed that people will. I would like to make this more specific. Is anyone, including you, willing at this point in the
analysis to claim a significant discrepancy with QCD? If so please say so. If not then you should also say so. The other point is whether or not the text might imply such a conclusion.</p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p>I was trying to caution you, and the collaboration, that the paper as written hints to me that the answer is yes. You may not mean this but I think that an objective reading of the conclusion of the text you sent implies
it. My suggested change is meant to eliminate any possibility of making such as impression.</p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p>The paragraph I mean is</p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p><span style="font-family: 'Times New Roman';" class="">Within the 1.7% total uncertainty our current preliminary result is in a good agreement with the chiral anomaly leading order prediction. However, it has a certain
tendency to disagree with the theory NLO corrections by a factor of 2.5 standard deviations (see Fig. 6).</span></p>
<p class="MsoNormal"><o:p class=""> </o:p>This discussion gives the impression that one can choose between the LO and NLO results as a test of QCD. This is not the case since only the NLO result as it now stands is the currently accepted prediction. I would
suggest that this conclusion be made very cautious.</p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p>Here is a suggested revision of this paragraph:</p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p>The current preliminary result is lower than the NLO, QCD prediction within the current 1.7% accuracy. It should be taken as a PrimEx2 progress report, not a claim of an experimental discrepancy.</p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal">I agree that we did not waste our time making this fundamental measurement with all of the work that is involved. I would not have worked so hard on this if I thought anything else.</p>
<p class="MsoNormal"> I agree that the very interested reader can calculate how many sigmas the preliminary result is below the NLO prediction. However this suggested change emphasizes to the reader not to do this since it 's not the final result. </p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p>I could discuss some other points in your note but I want to keep this as brief and simple as possible. If you or anyone else wants to discuss this we can use skype (I'm aron_bernstein_2)- perhaps on Wed. By the way
I think that the organizers will accept a few days delay particularly if you send them an e mail asking for a few days (I'm in a similar situation with my submission). I think that it's important to get this right.</p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal"><o:p class=""> </o:p>Regards,</p>
<p class="MsoNormal"><o:p class=""></o:p></p>
<p class="MsoNormal">Aron<o:p class=""></o:p></p>
<!--EndFragment-->
<div class="">
<div class="">Aron M. Bernstein<br class="">
Professor of Physics, Emeritus<br class="">
MIT<br class="">
Cambridge, MA 02139<br class="">
office: 26-419<br class="">
617-253-2386</div>
<div class=""><br class="">
</div>
<br class="Apple-interchange-newline">
</div>
<br class="">
<div>
<blockquote type="cite" class="">
<div class="">On Sep 28, 2015, at 6:12 PM, <a href="mailto:gasparan@jlab.org" class="">
gasparan@jlab.org</a> wrote:</div>
<br class="Apple-interchange-newline">
<div class=""><br class="">
Dear Aron,<br class="">
<br class="">
Thank you for your very valuable comments and useful questions. Same of<br class="">
them I agree with, and some needs further discussions. Let me try to do<br class="">
that as much as I can.<br class="">
I think any experiment should follow theory ONLY in the beginning,<br class="">
planning stage. No experimental result must follow the theory<br class="">
calculations. Otherwise, there is no need to do an experiment, and all our<br class="">
efforts for the past fifteen years are worthless in that case. As a<br class="">
matter of fact, the opposite is true: in the fundamental experiment<br class="">
(perhaps in any experiment) one needs to implement the "blind" method up<br class="">
to the very end result. We had started with that but, did not continue. I<br class="">
am sure, we all agree with this general approach. On this way, we already<br class="">
decided to do for the PrimEx-II result: both groups results, starting from<br class="">
the event yields, cross sections, fits and final numbers will be requested<br class="">
to have an open cross check before including any of them in the final<br class="">
average.<br class="">
<br class="">
Once we decided to show the current preliminary PrimEx-II result, then it<br class="">
has to be show in Figure #6 with its 1.7% uncertainty. Then, anybody can<br class="">
take 4.5%/1.7% = 2.65 ratio and get the same thing as we need to say<br class="">
ourselves about our result. To me, there is nothing to hide here. After<br class="">
all it is a Preliminary result as we are stating it in all places. I agree<br class="">
with your suggested sentence, which is basically the same only without<br class="">
mentioning this number. I think that it will be better to hear opinions<br class="">
from other PrimEx-II people before we change it.<br class="">
<br class="">
About the NLO as the only currently accepted prediction, and there is no<br class="">
LO prediction. This takes us as far as ten years back. As much as know,<br class="">
all we are talking here is the perturbation theory in quantum physics<br class="">
therefore, it has LO, NLO, NNLO, . and more. We have to accept all of<br class="">
published results pay respect to them. After all, the LO is a fundamental<br class="">
result from the chiral axial anomaly (with massless quarks only).<br class="">
<br class="">
About QCD based sum rule result: this note is a short proceeding, not a<br class="">
review and therefore we just mentioning it and showing the reference. By<br class="">
the way, we can not ignore a work from a peer-reviewed journal, not to<br class="">
talk about an author like Ioffe himself.<br class="">
<br class="">
I will include the suggested review paper in the text, I agree on that<br class="">
also (I am close to the 10 page limit already).<br class="">
<br class="">
Thanks again,<br class="">
Ashot<br class="">
<br class="">
<br class="">
<blockquote type="cite" class="">Dear Ashot,<br class="">
I think that the presentation of the PrimEx2 results as<br class="">
preliminary is a good idea as well as the inclusion of the fact<br class="">
that a second analysis is coming soon. I would suggest that the<br class="">
discussion about the preliminary results compared to the theory<br class="">
needs a little modification.<br class="">
Within the 1.7% total uncertainty our current preliminary result is in a<br class="">
good agreement with the chiral anomaly leading order prediction. However,<br class="">
it has a certain tendency to disagree with the theory NLO corrections by<br class="">
a factor of 2.5 standard deviations (see Fig. 6)<br class="">
This discussion gives the impression that one can choose between the LO<br class="">
and NLO results as a test of QCD. This is not the case since only the NLO<br class="">
result as it now stands is the currently accepted prediction. I would<br class="">
suggest that this conclusion be made very cautious. Here is a suggested<br class="">
revision of this paragraph:<br class="">
The current preliminary result is lower than the NLO, QCD prediction<br class="">
within the current 1.7% accuracy. It should be taken as a PrimEx2<br class="">
progress report, not a claim of an experimental discrepancy.<br class="">
In the long run, if indeed we significantly deviate from the NLO<br class="">
prediction, then it will be taken rather seriously by anyone in the<br class="">
larger physics community who pays attention. I'm sure that this is the<br class="">
case and the comments that I got privately from several theorists in the<br class="">
field who heard Ashot's CD15 talk strongly reinforced this opinion! This<br class="">
is the responsibility of an experiment that measures a fundamental<br class="">
quantity.<br class="">
If the final result of PrimEx2 is a serious disagreement with the NLO<br class="">
predictions we can expect a great deal of skepticism and scrutiny, first<br class="">
inside JLab and then in the larger community. I'm not saying that we<br class="">
should change our result or not report this preliminary value, just that<br class="">
we will have to work very hard to convince ourselves that our result is<br class="">
correct, and then to be prepared to have to convince others. We should<br class="">
take this preliminary result seriously and do our best to mobilize all of<br class="">
the resources that we are able to command and be prepared to commit the<br class="">
required time to see this process through.<br class="">
Getting back to the paper, here are a few suggested corrections:<br class="">
I would not say that the NLO corrections are small, just quote the result<br class="">
of Gamma increasing by 4.5 +\- 1.0 %.<br class="">
I would add our review article to Rory's excellent one<br class="">
A.M.Bernstein and Barry R. Holstein, Rev. Mod. Phys. 85, 49(2013).<br class="">
It should be pointed out that Ioffe's calculation did not take the eta'<br class="">
contribution into account. It is known that the eta' contributes ~ 1/3 of<br class="">
the 4.5% increase of Gamma. As it stands you have this contribution in<br class="">
the figure but properly do not mention it. As you know my practice is<br class="">
just not to include it in the figure. It can be mentioned in the text of<br class="">
a longer article if you want, explaining why it isn't included.<br class="">
It is nice to see all of the hard work getting reported.<br class="">
Regards,<br class="">
Aron<br class="">
Aron M. Bernstein<br class="">
Professor of Physics, Emeritus<br class="">
MIT<br class="">
Cambridge, MA 02139<br class="">
office: 26-419<br class="">
617-253-2386<br class="">
<br class="">
<br class="">
<br class="">
On Sep 27, 2015, at 6:12 PM, <a href="mailto:gasparan@jlab.org" class="">gasparan@jlab.org</a><<a href="mailto:gasparan@jlab.org" class="">mailto:gasparan@jlab.org</a>><br class="">
wrote:<br class="">
<br class="">
Dear PrimEx-2 collaborators,<br class="">
<br class="">
I put together a draft text for the Chiral Dynamics 2015<br class="">
proceeding. It is in the attachment of this email.<br class="">
<br class="">
We discussed this subject in the past two weekly group meetings<br class="">
and decided to publish our PrimEx-II results as a "Preliminary".<br class="">
This text is following our decision.<br class="">
<br class="">
Please take a look and let me know if you have any suggestion or<br class="">
corrections.<br class="">
(the text limit is 10 pages).<br class="">
<br class="">
I have to submit the text on Wednesday afternoon, sorry for this<br class="">
late note.<br class="">
<br class="">
Thank you,<br class="">
Ashot<br class="">
<br class="">
<br class="">
</blockquote>
<br class="">
<br class="">
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</blockquote>
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