Hi,
I can't come to Bates tomorrow. I have a dental appointment. It is my
first dental in three years, my teeth have been bothering me for weeks,
I already made the appointment after DOE review, so I am going no matter
what people say. And I am paying a good 200 bucks out of my own pocket so
its better be more than 1/2 hour.
I am on 1am shift Saterday. I can come up in the after noon on Friday, say
2 or 3 o'clock to sort things out.
But to cut the talk short, I want to point out 8 things:
1. I realized that the 0.53/C I quoted is probably misleading. This is the
event rate withing an azimuthal angle range of +-10 degrees. If you ever
looked at azimuthal angle distribution in either ep elastic or ed elastic,
you will see the acceptance starts at +-15 degree, however, the flat
region spans only +-10 degree. In 10 to 15 degree region it is the fall
off from the plateau to 0. This fall off hints things not as good in
tracking, therefore I opt to exclude these event in analysis. Please see
the attatched figure xs_phi.eps. I confirmed with Chris, he sees the same
thing in ep elastic. Chris also confirmed the bump at -10 deg when
electron goes to left. What is the cause we don't know, probably tracking.
With this bunch included, I get 0.63/C. which is closer to Genya's number.
Probably this is the proper base for comparison between me and Genya.
2. With item 1 in mind, I would scale Genya's 0.75/C down a little bit to
compare with my 0.53/C. It happens that 0.75/0.63*0.53 = 0.63/C. So the
difference between me and Genya is 19%(of 0.53), not 50%. What is this
19%? I don't know. I believe I have tigher cuts. I have shown
experimental cross sections in Q2 and electron scattering angle. In low Q2
region, the match in shape with Monte Carlo is pretty nice except for
a 15% loss in right sector low Q2. If any one knows how to recover that
chunk, please do generously let me know. I send these plots again in both
linear and log scale to support my claim that I determine the rates to a
reasonable extend. Please find: xs_Q2.eps, xs_Q2_log.eps, xs_th.eps,
xs_th_log.eps in atatchment.
3. Since I have compared and reached agreement in my MC with proposal in
terms of counting rates, I would say, even 0.75/C does not translate to
5e31. If I believe MC then Genya's 0.75/C corresponds to 1.6e31. Since I
rationalized my rates form MC with Zilu's rate calculation, I think I m
on firm ground here.
4. Now as a middle step. I take Genya's Pzz=0.8, take the scaled down
0.63/C. The "projected" error bar will be 0.69 the size of my
"projection", not a FACTOR OF 3 SMALLER.
This also shows that reversed field running will have to be longer than
50kC if there is going to be any to make any difference.
5. Now coming to Pzz. I have a good piece of news. More recent
runs(8648-9313) have higher Pzz than the runs I based my extrapolation
on(8479-8598). The new runs have Pzz=0.67+-0.03. I did not have a chance
to digest the data taken in last couple days yet.
6. This is still not in accord with 0.8 within +-10% systematics. I would
venture to suggest it s time for another holding field survey. I looked at
data again and again the last two days because I do not want to discredit
my "neat trick" by abusing it. if I could be spared to argue against 5e31
lumi, I could have done this sooner.
7. I suspect the target spin angle now is 30+-1 deg, not 32!
I want to use the following fact to support this claim. Here are the fits
for Pzz with 30 and 32 deg spin angle, in the two sectors, normalized
to various bins:
fit to 3 bins fit to 1st bin fit to 2nd bin
30 deg: parallel 0.67+-0.06 0.65+-0.09 0.68+-0.09
perpend 0.66+-0.03 0.71+-0.04 0.66+-0.05
average 0.67+-0.03 0.68+-0.04 0.64+-0.05
32 deg: parallel 0.54+-0.05 0.56+-0.08 0.51+-0.08
perpend 0.73+-0.03 0.75+-0.05 0.72+-0.05
average 0.66+-0.03 0.67+-0.04 0.62+-0.05
With Abbott being God, 32 degree yields meassurements of Pzz from two
sectors in no ways compatible with each other. With fit to 3 bins
together, fit to 1st bin, fit to 2nd bin, the difference in Pzz_para and
Pzz_perp are: 2.4-sigma, 1.5-sigma, 1.6-sigma. But in any case different
fit in same sector yield same answer.
Yet fits with 30 degree assumption are cross the board very consistant.
Worst case is 0.77-sigma.
Are we sure spin is 32 degree to the left?
8. This is just my speculation.
If you look at 32 deg, perpendicular kinematics in item 7 for Pzz, you
see 0.72-0.75 for Pzz. If all unfortunate happened at the same time,
that is, if one took 32 deg without cross checking, if one used only
perpendicular kinematics because the asymmetry is larger, if one adopted a
model with smaller T20, one would easily get Pzz>=0.8.
In summary of rate issue, I think, claim of 5e31 luminosity is
questionable, I believe e'p, e'n channel do not support that claim
either. Difference in rate estimation between Genya's and mine is not as
dramatic as we thought and it would be a better make believer if cross
section vs. Q2 can be shown instead of just a lump sum rate number.
In summary of Pzz issue, perhaps we should open the chamber and meassure
the field again. With wrong assumption of spin angle and a systematically
small model, one would get Pzz>=0.8 in perpendicular kinematics. I
think it is worth checking. Remember last time I said spin angle was not
what it s claimed to be? :)
Chi
On Wed, 28 Jul 2004, Michael Kohl wrote:
> Continue running polarized Deuterium. Injection current is 155 mA.
>
> Genya suggests to measure (normalized) unpolarized elastic ep cross
> section, once with regular setup and once with a minimal setup (i.e. only
> two TOF paddles turned on) in order to clarify a miracle about count
> rates, i.e. to exclude any problem introduced by the trigger hardware.
> This is doable within less than a shift. Genya also reports a difference
> in ed count rate on the order of 50% in his analysis compared to the one
> of Chi.
>
> We will have a meeting upon this issue some time next week, AFTER Genya
> and Chi will have clarified their ed rates among each other.
> Genya and Chi should do this as soon as possible.
>
> Regards,
>
> Michael
>
>
>
> --
>
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