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<div class="moz-cite-prefix">Francois, Maxime, and folks,<br>
<br>
There is no question that running everything in one run period
with a perfectly understood detector would be ideal, in principle.
But that is just not going to happen unless we want to wait until
after the year 202x (x=3, 4,..?). There is just no way of
scheduling 100 PAC days for RG-K or 140 PAC days for RG-A in one
string. The best realistic option will be to run RG-K in 2 periods
with two different energies. That means we still have to
understand the systematic for the two energies independently as we
will be taking data year(s) apart, and the detector performance
will have changed, background will be different, etc.,etc. <br>
(Knowing that I ask why everyone agreed to use the 28 days of RG-K
(now down to 18days) at these two odd energies. Noone forced us to
do it, we could have just sat these 4 weeks out. )<br>
<br>
Now we should make best use of this opportunity to better define
our running conditions, triggers, etc,. and this is what we is
currently going on. In my view these few days are actually not
lost time for RG-K. If we can take at least some decent amount of
data at two different energies, and under very similar detector
condition, we may be able to test the systematics under these
close to ideal conditions. <br>
<br>
All the best,<br>
Volker<br>
<br>
<br>
<br>
On 10/27/18 10:36 AM, mdefurne wrote:<br>
</div>
<blockquote type="cite"
cite="mid:f4ea14ce-d916-bd39-b73b-263bc60dab6b@jlab.org">
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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">
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<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>
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<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>
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<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>
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