[G8b_run] Tagger Sag

[Michael Dugger]

Hi,

This might be good to figure out for future cooking of other run periods.

For g8b, we are nearly finished fixing the energies. Barry and I have 
been working with FSU to check that the energy corrections are as good as 
presented by Chuck. So far, we are satisfied that all is well, and expect 
to be done looking at the results by Monday.

Take care,
Michael


On Fri, 23 Oct 2009, Eugene Pasyuk wrote:

> The exact correction described in this paper is implemented in the
> tagger reconstruction code. Unless there was some glitch and it did not
> work. I'll double check if it was applied.
>
> -Eugene
>
> Barry Ritchie wrote:
>> Volker, though I'd heard about the sag long ago, I was unaware of this
>> paper.
>>
>> At any rate, since "the saga of the sag" continues as the deformation
>> seems to continue to grow, every run group should do what we've been
>> doing. I think this is contrary to the conclusion reached in the paper,
>> though:
>>
>> "The analysis presented in Ref. [3] was repeated with the new
>> calibration constants and showed similar improvements in the energy
>> determination. The data in Ref. [3] were from a 1999 CLAS run, while the
>> data used in this analysis and the data presented in Fig. 12 were taken
>> in 2004. Comparison of these two sets of data shows that the geometry of
>> the tagger focal plane did not change during this five year period and
>> that the sagging and misalignments were introduced at the time of the
>> tagger construction."
>>
>> Brian Vernarksky's analysis would also suggest the sag is changing, if I
>> understand him correctly.
>>
>> BTW: Notice that the variations observed in Figure 12 are on the order
>> of +/- 2 MeV or so.
>>
>> ---BGR
>>
>>
>>
>> Professor Barry G. Ritchie
>> Department of Physics
>> Arizona State University
>> Tempe, AZ  85287-1504
>>
>> Telephone: (480) 965-4707
>> Fax: (480) 965-7954
>>
>> -----Original Message-----
>> From: g8b_run-bounces at jlab.org [mailto:g8b_run-bounces at jlab.org] On
>> Behalf Of Volker Crede
>> Sent: Friday, October 23, 2009 1:29 PM
>> To: g8b
>> Cc: Volker Crede
>> Subject: [G8b_run] Tagger Sag
>>
>> Hi all,
>>
>> Mukesh Saini in our group has just pointed out that there has been a
>> 2007
>> NIM paper on the "Energy calibration of the JLab bremsstrahlung tagging
>> system" by some CLAS members (S. Stepanyan et al.): NIM A 572 (2007)
>> 654.
>> I tried to attach it to the email, but the file is too  big. They
>> describe
>> a tagger photon-energy correction for CLAS which is needed to account
>> for
>> a possible sag of the frames holding the E-counters. They say there was
>> "corroborating evidence from simulations of the effects of gravitational
>>
>> sagging and various possible misalignments of the tagger focal plane".
>> Figures 11 and 12 look very similar to our tagger sag plots.
>>
>> Mukesh has been working on the tagger calibration for g12 and pointed
>> out
>> (he believes) that the correction is in the tagger package for g12 and
>> possibly for all runs after 2007. According to Mukesh, we can simply
>> look
>> into the tagger code and find out what the correction is.
>>
>> I will have a closer look at the paper over the weekend. Is anybody else
>>
>> aware of this publication? I hope it's not just us ...
>>
>> Best wishes and have a good weekend
>>
>>     Volker
>>
>> ----------------------------------
>>
>> Volker Crede
>> Assistant Professor
>> Florida State University
>> Department of Physics
>> 206 Keen Building
>> Tallahassee, FL  32306  USA
>>
>> Phone: 001 850 644-2423
>> Fax: 001 850 644-4478
>> crede at fsu.edu
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