<div dir="ltr">Dear Volker<div><br></div><div>I completely agree with this suggestion. We did some tests in the past with event by event likelihood. Assigning negative likelihood to background events we were able to cross check asymmetries. It would be even better to do this at the level of amplitudes and CFFs. This is not something that can be demonstrated in a couple days however. It will requires time to move in this direction. </div><div><br></div><div>Nevertheless, even with the best possible analysis, it still remains true that combining short amounts of data taken months or years apart will be detrimental to our systematics. During our PAC presentation we were challenged in our supposed aggressive estimation of systematics, on the basis of the published systematics from e1dvcs. It was always clear to me that we should aim to improve the systematics we had in the past, and I think we have reasons to believe we can do so. This public challenge in front of the PAC from the very people in charge of scheduling now puts us naturally in a position to be reluctant to agree to increased systematics. Our proposal already has the most challenging analysis of the approved exclusive program. I think our proposal deserves to be scheduled in full and not as convenience to fill in between other experiments. </div><div><br></div><div>Best regards</div><div>FX</div></div><br><div class="gmail_quote"><div dir="ltr">On Fri, Oct 26, 2018 at 6:42 PM burkert <<a href="mailto:burkert@jlab.org">burkert@jlab.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div class="m_1606524247700921737moz-cite-prefix">Hi Maxime, <br>
<br>
I can understand that if we keep working with binned data sets
that changing the energy can create such issues. However, is this
the way we want to continue, instead of moving towards non-binned
data analysis, which I think will not have these same issues and
allows more flexibility in the final physics analysis? We should
explore this possibility more. <br>
<br>
Volker<br>
<br>
<br>
<br>
On 10/26/18 12:03 PM, mdefurne wrote:<br>
</div>
<blockquote type="cite">
<p>Dear Volker,</p>
<p>I completely agree with F-X about the recommendation of keeping
the beam energy as stable as possible. And I agree that
combining this two "data set" might significantly increase the
systematics. This kind of exercise is extremely complicated and
the final results tends to be extremely sensitive to the overall
systematics. (You can trust me on this for having done it in
Hall A and it was with a much simpler experimental setup.)</p>
<p> Kind regards,</p>
<p>Maxime<br>
</p>
<div class="m_1606524247700921737moz-cite-prefix">On 25/10/2018 19:37, Francois-Xavier
Girod wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Dear Volker
<div><br>
</div>
<div>The DVCS group has some experience combining datasets at
6.75 and 6.88 GeV. It does actually require caution and
should be evaluated carefully before stating that we can
accept such differences of 100 MeV or more. The issue is not
simply that the cross-section changes, which can affect the
real part of the amplitude, but the issue is also that the
kinematics change. Q2 is not the same in xB and theta bins.
Of course we can attempt to correct for this by changing the
binning in theta to keep Q2 fixed, but then we also change
xB... And in the end, even if we somehow manage to keep xB
and Q2 both fixed, we will still have a change in epsilon
which enters the Rosenbluth separation when combining beam
enegies. </div>
<div><br>
</div>
<div>In writing our proposal we do not have strong constraints
on the absolute beam energy, but we do have an expectation
that the energy will be fixed at better than the MeV level.
Combining beam energies as far as 100 MeV will for certain
affect our systematical uncertainties. If we really have to
work with this, then we must do our homework and put a
number on this. I do not think it is a straightforward
exercise however.</div>
<div><br>
</div>
<div>Best regards</div>
<div>FX</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr">On Thu, Oct 25, 2018 at 1:15 PM burkert <<a href="mailto:burkert@jlab.org" target="_blank">burkert@jlab.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div class="m_1606524247700921737m_3725191116230764221moz-cite-prefix">All,<br>
<br>
I agree with intention of the text. However, I suggest
to downplay the 6.5 vs 6.4 GeV. I don't think it is such
a big deal and we have to deal with that later again as
the machine energy will never be exactly the same as in
previous run periods. We have to learn how to deal with
slight energy variations in an effective way. <br>
<br>
Typo: In the next to last paragraph please delete the
first "during" in the string " <span> during as soon as
possible during the November RG..</span> <br>
<br>
Regards,<br>
Volker<br>
<br>
<br>
On 10/25/18 7:41 AM, Annalisa D'Angelo wrote:<br>
</div>
<blockquote type="cite">Dear All, <br>
<br>
after last RGK meeting, some additional thinking and
exchange of information with Raffaella, I have put
together a draft letter to answer the CCC request
information, which you may find at: <br>
<br>
<a class="m_1606524247700921737m_3725191116230764221moz-txt-link-freetext" href="https://userweb.jlab.org/%7Eannalisa/hybrid_baryons/RGK_response_to_CCC.docx" target="_blank">https://userweb.jlab.org/~annalisa/hybrid_baryons/RGK_response_to_CCC.docx</a>
<br>
<br>
In a nut shell I would like to propose that the new
trigger requiring a central hadron could be implemented
and commissioned as soon as possible during RGA, not to
loose time during our assigned RGK data taking. RGA
could take all the Spring data taking in return. <br>
<br>
This would optimize the overall efficiency. <br>
<br>
Please let me know your opinion on the matter. <br>
<br>
Any comment/correction/suggestion is highly appreciated
<br>
<br>
All the best <br>
<br>
Annalisa <br>
<br>
p.s. we may discuss the matter tomorrow at the RGK
weekly meeting. <br>
<br>
<br>
</blockquote>
<p><br>
</p>
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