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Everyone,<br>
<br>
Here is a massage from Nathan. Major bugs in gem package <br>
have been found and are in process of fixing.<br>
<br>
Stepan<br>
<br>
-------- Original Message --------
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Subject: </th>
<td>Re: [Eg6_analysis] rtpc alignment</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">Date: </th>
<td>Mon, 03 Sep 2012 22:18:08 -0500</td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">From: </th>
<td>Nathan Baltzell <a class="moz-txt-link-rfc2396E" href="mailto:baltzell@anl.gov"><baltzell@anl.gov></a></td>
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<th align="RIGHT" nowrap="nowrap" valign="BASELINE">To: </th>
<td>Stepanyan Stepan <a class="moz-txt-link-rfc2396E" href="mailto:stepanya@jlab.org"><stepanya@jlab.org></a></td>
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<pre>Hi Stepan,
I had a fun few days with gem package lately:
<a class="moz-txt-link-freetext" href="http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/GEM_Bugs">http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/GEM_Bugs</a>
I had made assumption that things were working generally as expected.
It's now obvious that that was an awfully bad assumption. I remember
you warning me about the gem package almost one year ago.
None of these bugs appear to be L/R asymmetric, and their combined
effect may be rather large, so probably it is not worthwhile to pursure
the L/R issue for the moment.
I supsect it is necessary to revisit all RTPC calibrations. It is not
straightforward to assess how all these changes combined will affect
reconstructed tracks, gain calibration, or driftpath calibration without
larger statistic than I have been using for my detailed investigations.
Check out that wiki page and let me know if you have any questions or
comments. And feel free to forward this to the eg6analysis mailing list
if you think that would be constructive.
Thanks,
Nathan
On Fri, 31 Aug 2012 06:09:34 -0500, Stepan Stepanyan <a class="moz-txt-link-rfc2396E" href="mailto:stepanya@jlab.org"><stepanya@jlab.org></a>
wrote:
> Nathan,
>
> Thanks a lot for the quick turnaround. I agree misalignment seems
> cannot explain discrepancy. But still we need to understand why L/R
> momenta are so different, 10-20%. Are track lengths similar, I assume
> we have the same pad geometry in both sides.
>
> Regards, Stepan
>
> On 8/30/12 11:02 PM, Nathan Baltzell wrote:
>> Dear All,
>>
>> Continuing the discussion from today's meeting regarding
>> the possible effect of misalignment on momentum, I looked
>> into the reconstruction code and made some estimates from
>> the magnetic field map.
>>
>> For details:
>> <a class="moz-txt-link-freetext" href="http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/Alignment">http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/Alignment</a>
>>
>> To summarize:
>> The effect should be a few-percent error on momenterm per cm
>> of misalignment due to picking the incorrect magnetic field
>> from the map. It's dependent on polar angle, but at elastic
>> kinematics we would need much greater than 1cm of misalignment
>> for this effect to wholly account for the L/R momentum
>> discrepancy we see in the data.
>>
>> -Nathan
>> _______________________________________________
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</pre>
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