[g13] g13b data quality: run by run diagnostics
Daria Sokhan
daria at jlab.org
Thu Jan 10 17:51:14 EST 2013
Hi Nick,
Yep, I'm, just working on the graphs of the plot parameters -- the
problem is that some of the distributions have high stats and a very
clear asymmetry, but because of the small error bars the chi-sq/ndf is
sometimes pretty large, so the value by itself is misleading, while
other have very low stats, consequently huge error bars, points all
over the place and a chi-sq/ndf close to 1 but could equally well have
been fit with a platypus. Perhaps I'm messing up my errors somehow,
but I'll superimpose graphs of the chi-sq/ndf from both a
straight-line fit and a cos2phi. If there really is a pronounced
asymmetry, the two should be vastly different.
Regarding absolute value of asym, it's not very meaningful as it's
summed over all kinematics for each run and the plots on the Wiki so
far aren't scaled by polarisation. And the edge jumped about a lot, so
comparison between runs under the same setting might be misleading.
But I'll produce those as well, so we can see.
I'll try to call into the meeting next Monday -- otherwise let's skype
next week!
Cheers,
Daria
On 10 January 2013 22:22, Nick Zachariou <nickzachariou at gmail.com> wrote:
> That is great Daria. Do you by any chance have the plots of the determined fit parameters as a function of run number? I will look into it more later. Maybe we can talk sometime on skype? Or can you give an update next week during the g13 meeting?
>
> Thank you,
> Nick
>
> On Jan 10, 2013, at 4:38 PM, Daria Sokhan <daria at jlab.org> wrote:
>
>> Dear everyone,
>>
>> As part of good-run diagnostics I had promised to produce a beam
>> asymmetry from the gamma + d -> p + pi- + (p) reaction for every run
>> in g13b. I have now done that in two ways -- dividing each polarised
>> run by the nearest carbon (AMO) data, and also by combining
>> neighbouring PARA and PERP data. The results from both methods, along
>> with details, can be found on the g13 Wiki:
>>
>> http://clasweb.jlab.org/rungroups/g13/wiki/index.php/Raw_asymmetries_by_run_and_polarisation_plane_--_DIAGNOSTICS
>>
>> In brief, it looks like there is enough statistics to use this for
>> data-quality diagnostics for the lower coherent edge positions (up to
>> about 1.9 GeV), but above that the distributions look progressively
>> messier as the coherent edge rises higher. I haven't been able to get
>> round this yet, but there are some thoughts on the matter on the Wiki.
>> At the moment I produced the raw asymmetries without trip cuts,
>> without assigning the real polarisation and without cutting around the
>> coherent peak. I am just adding those stages and will send an update
>> when that's done.
>>
>> Cheers,
>> Daria
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