<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">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_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_3725191116230764221moz-txt-link-freetext" href="https://userweb.jlab.org/~annalisa/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>
</div>
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