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Yes, it was a recommendation of TR to use the room temperature target. We still can vary the pressure if needed.</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Tdis <tdis-bounces@jlab.org> on behalf of Jan C. Bernauer <jan.bernauer@stonybrook.edu><br>
<b>Sent:</b> Tuesday, August 11, 2020 4:03 PM<br>
<b>To:</b> tdis@jlab.org <tdis@jlab.org><br>
<b>Subject:</b> Re: [Tdis] [EXTERNAL] Inconsistencies in the TDIS proposal: Some things I found</font>
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<p>Hi all,</p>
<p>Could somebody quickly confirm that we'll indeed run at room temp, so with roughly 0.7e36 instead of 3e36 /cm^2/s?</p>
<p>Thanks,</p>
<p>Jan<br>
</p>
<p><br>
</p>
<div class="x_moz-cite-prefix">On 8/6/2020 11:43 AM, Jan C. Bernauer wrote:<br>
</div>
<blockquote type="cite">Hi Tim, Hi Wally, Hi TDIS, <br>
<br>
Sorry for the lengthy email. <br>
<br>
Some updates and questions to my talk: <a class="x_moz-txt-link-freetext" href="https://hallaweb.jlab.org/wiki/images/2/2f/TDIS_sim.pdf">
https://hallaweb.jlab.org/wiki/images/2/2f/TDIS_sim.pdf</a> where I found what I believe are internal inconsistencies, and differences to my own implementation of F_2, f_\pi, and a full MC.
<br>
<br>
Wally, Tim, I also send this to you, because I believe you might have additional insight to the source of some of these figures/values.
<br>
<br>
<br>
0) Does anybody have the exact bins used for the projected result figures? Especially the one as a function of t. That would be very helpful!
<br>
<br>
1) I do see about a factor of 2 more inclusive CS than in the proposal. I think it's likely that this error is on my end, I have to verify with g4SBS. In any case, the code version I got from Carlos (Thanks!), authored from Tim and Wally, do not calculate that
as far as I can tell. It's not helping us in any case, we would just need less current I'd assume.
<br>
<br>
2) It would be great to figure out in which configuration the code was for the generation of table 6 and 7. I assume it was this code I attach here? Is that the code version after a factor 2 has already been found? I believe so, because I can get the F_2^{\pi
p} plots out that are in the new proposal, which are higher than the old proposal.
<br>
<br>
Some things which I found in the code which do not match the experiment: <br>
<br>
Theta_e is ~12, not 35 degrees. That only affects the calculation of Q^2, which is slightly affecting the proton PDFs. Can't explain a big difference.
<br>
<br>
The code was set up for pi^+, I'm looking at pi^0, so I changed the isospin factor to 1. I changed some other integration ranges (ymax=1, xmax=0, km1, km2 ), and also implemented a cosph cut (proton theta<70)
<br>
<br>
With these changes, I match exactly (on a log scale :) ) my own implementation and the plots in the new proposal.
<br>
<br>
3) BUT the ratio was still off. I traced it down to F_2^p. The relevant lines are here:
<br>
<br>
CALL SETCTQ6(1) ! CTEQ 'MS-bar' SCHEME. <br>
u_pro = CTQ6PDF (1, REAL(x), SQRT(REAL(Q2))) <br>
ubar_pro = CTQ6PDF (-1, REAL(x), SQRT(REAL(Q2))) <br>
d_pro = CTQ6PDF (2, REAL(x), SQRT(REAL(Q2))) <br>
dbar_pro = CTQ6PDF (-2, REAL(x), SQRT(REAL(Q2))) <br>
<br>
F2neu = 2.*x * ((4./9.)*(d_pro + dbar_pro) <br>
& + (1./9.)*(u_pro + ubar_pro)) <br>
<br>
<br>
a) LHAPDF 6 and this code has a different definition for what PID=1 and 2 are. That stumped me for a while, but I'm pretty sure u_pro is indeed the proton u PDF.
<br>
<br>
b) For the neutron, d_neu=u_pro and vice versa, so the line actually reads 2 *x * ( 4/9 ( u_neu +ubar_neu) + 2/9 ( d_neu +dbar_neu)). I changed it back to be correct for the proton.
<br>
<br>
c) BUT: I do not have the 2 there. Where does that come from? I'm not super versed in PDFs, but it is my understanding that that shouldn't be there. If not, can anybody please explain?
<br>
<br>
( d) There is also a small difference in the code here and LHAPDF for x<0.1. 10% or so. That must be in the underlying PDF or Q^2 evolution)
<br>
<br>
In any case, without the 2, my code and this code essentially agree on F_2^p (with Q^2=1, very close to the plots in the proposal. With Q^2 changing, slightly different from the proposal, maybe 30% at most, but both codes the same way. Makes me think that the
proposal line comes from a different program, which might explain the discrepancy with the 2).
<br>
<br>
<br>
4) Going back to table 6. We already know that it was not updated from the first proposal, so it likely already has a factor of 2 missing in the F/F ratio. With this additional factor 2, we are getting very close to what my program has, 4 is close enough to
5 that I would believe the rest is acceptance, slightly different cuts, etc, or the first factor 2 was actually 2.5 or something.
<br>
<br>
With these changes, both my code as well as the code I got from Carlos, modified as described above, gives a ratio F/F of 550 for the first line in the text. This assumes we accept k between 60 and 500 Mev, x between 0.05 and 0.2, at around 12 degrees, with
30 to 70 deg proton angle. This is also the number my MC gets, and roughly what I would get looking at the plots. Or is there some other cut that should be applied? Cut on z (y in the code)?
<br>
<br>
TLDR: If all my assumptions are correct, we see indeed 5.5 times more TDIS events (per DIS event) than we thought!
<br>
<br>
Let me know what you think! <br>
<br>
Best, <br>
<br>
Jan <br>
<br>
<br>
Attached: TDIS_orig.f, code I got from Carlos. TDIS.f: Code with my modifications.
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</blockquote>
<pre class="x_moz-signature" cols="72">--
Dr. Jan C. Bernauer
Assistant Professor
Department of Physics and Astronomy
Stony Brook University
Stony Brook, NY 11794-3800 </pre>
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