Hi Brad,<br><br>I had talked to Zein-Eddine and he had a few suggestions. The first thought that he had was that with a traget length of ~40cm there could be a large energy loss from events that scatter near the front of the target as compared to those that scatter at the end of the target. I took a look in the particle book at the energy loss (MeV cm^2/g) through liquid H2 for protons <=1Gev and we do sit right on the slope. <br>
<br>Another thought that he had was that the HRS was set to an angle of 46.2 degrees, not 45 and had a cetral momentum of 0.87 GeV. He was wondering if maybe we are not centered on the acceptance of the H2 elastic scattering with 1.12GeV beam.<br>
<br>The trigger prescale for the T5 on these events is 1 and the rate is ~82Hz<br>In addition to the T5 trigger cut I also cut out the eldtp<br><br>The beam cut is just a cut on the beam current. It is a cut around the average 14.75uA with a +/-1 spead. So all events within +/-1 of 14.75uA are counted. I took a look at the beam current for all the elastic runs and with the exception of 1259 they all looked stable. I did check and it is the T5 cut that is responsible for killing 90% of the events.<br>
<br> I just want to clarify that the no cut events, realy have no cuts, They were replayed using the analyzer with an empty cdef file, (where most that I have seen have an automatic trigger cuts in the cdef, requiring a T1 || T2 || T5 ect. )<br>
<br>And in the past when comparing how many reconstructed tracks I find in bigbite I would compare to these no cut events, which I now think does not make any sense. I should be comparing how many reconstructed tracks there are with respect to some events that staisfy the hardware trigger (ie t2, t5 ect)<br>
<br><br><div class="gmail_quote">On Wed, Apr 28, 2010 at 1:06 PM, Brad Sawatzky <<a href="mailto:brads@jlab.org">brads@jlab.org</a>> wrote:<br><blockquote class="gmail_quote">
<div class="im">On Tue, 27 Apr 2010, MATTHEW R POSIK wrote:<br>
<br>
> I have put together some kinematic plots for H2 elastic run 1258:<br>
><br>
> H2_L_BB.png shows the invariant mass sqrt(w2) (left), scattering angle<br>
> in degrees, and momentum in GeV . The red Hist is the HRS and the blue<br>
> histo is the BB. All plots here have T5 coin cut.<br>
><br>
> I then selected events in a tight cut on the BB elastic peak<br>
> "PriKineBB.W2>0.86&&PriKineBB.W2<0.96 && T5_coin_trigger" and plotted<br>
> the LHRS theta L.tr.tg_th this is plot lables el_th.png. As you can<br>
> see there are now 3 resolved peaks in the theta variable.<br>
<br>
</div>It smoothed out your previous theta plot a little, but the same<br>
structure is there... What are Zein-Eddine's thoughts on where that<br>
structure is coming from?<br>
<div class="im"><br>
> I also looked into the cuts that I was using for selecting good<br>
> protons in the LHRS. It seems that a lot of events are lost when I<br>
> make the LHRS acceptence cuts. Here is a run down of how the cuts<br>
> affect the events, the %diff is how many events are lost compared to<br>
> the trigger+beam cut, and the cut to cut % is how many events are lost<br>
> from the previous cut. The tg_xx are the acceptence cuts:<br>
><br>
> *********************************************************************<br>
> Cut<br>
> Events %diff from cut to cut<br>
> *********************************************************************<br>
> - no cut<br>
> 4009380 -<br>
> - triggers+beam<br>
> 216022 -<br>
<br>
</div>It looks like 90% of the data disappear with the triggers+beam cut.<br>
What were the prescales and individual trigger rates? What are the<br>
beam cut(s)?<br>
<br>
> - triggers+beam+track<br>
> 214883 0.50 0.50<br>
<div class="im">> - triggers+beam+track+tg_y<br>
</div>> 142087 34.20 33.88<br>
<br>
This seems odd to me since at 45 degrees the HRS can not see the target<br>
windows. This cut says that 1/3 of the data reconstructs 'outside' the<br>
valid target region... I had assumed the HRS was cleaner than that. Can<br>
Zein-Eddine or Gregg comment on whether it is typical to loose 1/3 of<br>
the data for elastic data at this stage?<br>
<div class="im"><br>
> -triggers+beam+track+tg_y+tg_ph<br>
> 112676 47.84 20.69<br>
> -triggers+beam+track+tg_y+tg_ph+tg_th<br>
> 65533 69.66 41.84<br>
<br>
</div>That's a big loss on the tg_th cut (also seen in your earlier slides).<br>
Given that the structure doesn't go away when you apply LHRS and BB<br>
kinematic cuts, it seems like those are real eP events... (Still need<br>
to understand the structure though.)<br>
<div class="im"><br>
> -above +ex_tg_p<br>
> 65309 69.77 0.30<br>
> -above +ex_tg_p+energy<br>
> 53235 75.36 18.49<br>
> -above +ex_tg_p+energy+cer<br>
</div>> 50852 76.46 4.47<br>
<div class="im">> -above +ex_tg_p+energy+cer+vdc<br>
> 47832 77.85 0.594<br>
> -above +ex_tg_p+energy+cer+vdc+prl<br>
> 11339 **Don't think this one is correct.<br>
> It requires prl1 and prl2 to fire.***<br>
><br>
> -without acceptance cuts<br>
> 152197<br>
><br>
> I also realized my prl cut is probaly not good, I required both prl1<br>
> and prl2 to fire. But if the proton deposits all it's energy in prl1<br>
> than it will not count. So I am going to take that cut out.<br>
<br>
</div>That is correct.<br>
<br>
-- Brad<br>
<font color="#888888"><br>
--<br>
</font><div><div></div><div class="h5">Brad Sawatzky, PhD <<a href="mailto:brads@jlab.org">brads@jlab.org</a>> -<>- Jefferson Lab / Hall C / C111<br>
Ph: 757-269-5947 -<>- Fax: 757-269-5235 -<>- Pager: <a href="mailto:brads-page@jlab.org">brads-page@jlab.org</a><br>
The most exciting phrase to hear in science, the one that heralds new<br>
discoveries, is not "Eureka!" but "That's funny..." -- Isaac Asimov<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Matthew Posik<br>Email: <a href="mailto:posik@temple.edu">posik@temple.edu</a><br>Temple University Physics Dept.<br>Office: BA-319<br>Office #: 215-204-1331 <br>
WebSites:<br>Temple:<br><a href="http://quarks.temple.edu/">http://quarks.temple.edu/</a><br>d2n:<br><a href="http://hallaweb.jlab.org/experiment/E06-014/">http://hallaweb.jlab.org/experiment/E06-014/</a><br><br>