<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<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="moz-cite-prefix">On 8/6/2020 11:43 AM, Jan C. Bernauer
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:cf44dd71-a72e-721e-44f4-a2bdbbb8de99@t-online.de">Hi
Tim, Hi Wally, Hi TDIS,
<br>
<br>
Sorry for the lengthy email.
<br>
<br>
Some updates and questions to my talk:
<a class="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.
<br>
<br>
<br>
<br>
<br>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
Tdis mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Tdis@jlab.org">Tdis@jlab.org</a>
<a class="moz-txt-link-freetext" href="https://mailman.jlab.org/mailman/listinfo/tdis">https://mailman.jlab.org/mailman/listinfo/tdis</a>
</pre>
</blockquote>
<pre class="moz-signature" cols="72">--
Dr. Jan C. Bernauer
Assistant Professor
Department of Physics and Astronomy
Stony Brook University
Stony Brook, NY 11794-3800 </pre>
</body>
</html>