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<p>Dear Volker,</p>
<p>I could not agree more with F-X again. Although we indeed
consider going for an unbinned analysis for the current RG-A, I am
absolutely no expert yet to know how robust it is with merging two
data sets with different beam energy: But I sincerely doubt that
it can be completely blind. Moreover it is the very purpose of
this proposal to study the beam energy dependence: Increasing
systematics on the beam energy that will give us the largest lever
arm with the 10.6 GeV data is taking a terrible risk. I stand with
F-X to argue that the very success of our proposal lies on our
control of systematics. Therefore it is our duty as spokesperson
of this proposal to stand against this splitting of our data
taking resulting most likely in the highest source of systematic
uncertainty (if we split the data taking). <br>
</p>
<p>Kind regards,</p>
<p>Maxime <br>
</p>
<div class="moz-cite-prefix">On 27/10/2018 01:04, Francois-Xavier
Girod wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAOKxh46jbe_HwFjZkU5GDsXm+fg9_GZWT_HUDa6w9qXzDUadxA@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<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" moz-do-not-send="true">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" moz-do-not-send="true">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" moz-do-not-send="true">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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