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<TITLE>Re: [G14_run] Systematic uncertainties on asymmetries - (Tsuneo's question to K Sigma analysis note)</TITLE>
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<FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Nick,<BR>
<BR>
A systematic scale uncertainty represents a shift to the entire data set as a hole. For example, imagine you find out after publication that a polarization (beam or target) was to high by 5%. How do you correct that – you multiply every data point by 0.95. Essentially, that just changes the scale of the axes in a plot of the data. The point-to-point statistical fluctuations do not change. That is not the equivalent to increasing the size of the point-to-point fluctuations.<BR>
<BR>
Now there can be some components of the systematic uncertainty that change with kinematic bins, and these parts could be added in quadrature with statistical errors. But those do not usually dominate the total systematic error. For this reason, when it comes time to publish, point-to-point systematics and scale uncertainties should be clearly quoted separated – as we have done in our recent pi-p PRL.<BR>
<BR>
Andy<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
On 11/7/17, 11:02 PM, "Nicholas Zachariou" <<a href="nicholas@jlab.org">nicholas@jlab.org</a>> wrote:<BR>
<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Hi Andy,<BR>
<BR>
Can you elaborate why its not correct to add the systematic in quadrature with the statistical? <BR>
I am not sure I understand why this "uses data that dont represent the experiment". Maybe we can talk more during the g14 meeting.<BR>
<BR>
Nick<BR>
On Nov 7, 2017, at 22:22, "Dr. A.M. Sandorfi" <<a href="sandorfi@jlab.org">sandorfi@jlab.org</a>> wrote:<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'>Hi Eugene,<BR>
<BR>
Yes, your point is well taken - for those data points where the asymmetry is<BR>
very close to zero. One has two choices: we could either give an overall<BR>
fractional (%) uncertainty, while quoting the absolute value as an exception<BR>
when the asymmetry vanishes, or just quote only an absolute uncertainty for<BR>
all points. <BR>
<BR>
The trouble comes at the subsequent stage when the data is used by the<BR>
various PWA groups. All PWA groups have their fitting routines set up to<BR>
float the scale of a data set while including a chi^2 penalty that is<BR>
weighted by a fractional systematic error. If we give them a systematic<BR>
uncertainty that is absolute, they will combine it in quadrature with the<BR>
statistical error to create an inflated point by point uncertainty, and set<BR>
the fitting scale to 1. I can guarantee that this will happen and it is a<BR>
completely incorrect way to use the data that doesn't represent the<BR>
experiment. So it is better to use the first approach - quote the systematic<BR>
uncertainty as a fractional (%) error, while explicitly noting the absolute<BR>
value of the systematic uncertainty for those asymmetry points with nearly<BR>
zero value. The later qualifying statement will probably be ignored in PWA<BR>
analyses, but at least most of the data will have been included properly.<BR>
<BR>
Andy<BR>
<BR>
<BR>
<BR>
<BR>
On 11/4/17, 11:37 PM, "Eugene Pasyuk" <<a href="pasyuk@jlab.org">pasyuk@jlab.org</a>> wrote:<BR>
<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
Any asymmetry can be anything between -1 and +1, 0 included. For any<BR>
observable which may be equal to 0 relative uncertainty does not make sense.<BR>
Only absolute uncertainty must be used.<BR>
The second term in Nick's equation is equal to 0 if ObservableValue is always<BR>
equal to 0 regardless of sigma_sys_relative. This is incorrect but good<BR>
illustration why one must not use relative uncertainty for asymmetries.<BR>
<BR>
-Eugene<BR>
<BR>
----- Original Message -----<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> From: "Tsuneo Kageya" <<a href="kageya@jlab.org">kageya@jlab.org</a>><BR>
To: "Nicholas Zachariou" <<a href="nicholas@jlab.org">nicholas@jlab.org</a>><BR>
Cc: "g14 run" <<a href="g14_run@jlab.org">g14_run@jlab.org</a>><BR>
Sent: Saturday, November 4, 2017 10:57:28 PM<BR>
Subject: Re: [G14_run] G14_run Digest, Vol 74, Issue 3 (Tuneo's question to<BR>
K Sigma analysis note)<BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> Nick,<BR>
<BR>
thank you for the response.<BR>
I would like to know why the absolute is more appropriate.<BR>
I will look forward the statements.<BR>
<BR>
Regards, Tsuneo Kageya.<BR>
<BR>
----- Original Message -----<BR>
From: "Nicholas Zachariou" <<a href="nicholas@jlab.org">nicholas@jlab.org</a>><BR>
To: "Tsuneo Kageya" <<a href="kageya@jlab.org">kageya@jlab.org</a>><BR>
Cc: "g14 run" <<a href="g14_run@jlab.org">g14_run@jlab.org</a>><BR>
Sent: Saturday, November 4, 2017 3:23:46 PM<BR>
Subject: Re: [G14_run] G14_run Digest, Vol 74, Issue 3 (Tuneo's question to<BR>
K<BR>
Sigma analysis note)<BR>
<BR>
Hi Tsuneo,<BR>
<BR>
The absolute error is propagated directly to the total uncertainty<BR>
(sigma_tot=sqrt(sigma_sys_absolute^2+(ObservableValue*sigma_sys_relative)^2 +<BR>
sigma_statistical^2).<BR>
<BR>
I can elaborate more if you like on why thats the case (why absolute are more<BR>
appropriate in my case). I will include some statements in the note to<BR>
reflect<BR>
this.<BR>
<BR>
Let me know if you would like to discuss this more.<BR>
<BR>
Best regards,<BR>
Nick<BR>
<BR>
On Nov 4, 2017, 19:12, at 19:12, Tsuneo Kageya <<a href="kageya@jlab.org">kageya@jlab.org</a>> wrote:<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> Hi Nick,<BR>
<BR>
Sorry to be late to make a question.<BR>
I have a question about the systematic error calculations.<BR>
<BR>
At page 35, on the table 4, you calculated the total absolute<BR>
systematic error<BR>
to be 0.10. How this is reflected into the total relative systematic<BR>
error ?<BR>
On the pi-p analysis, I think we calculated the systematic errors from<BR>
cuts in<BR>
the similar way and they are combined to the other errors (target and<BR>
beam polarizations).<BR>
Is this number 0.10 means 10 % or 0.1 % ?<BR>
<BR>
I may misunderstand this issue. Please let me know.<BR>
<BR>
Regards, Tsuneo Kageya.<BR>
<BR>
----- Original Message -----<BR>
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To: "g14 run" <<a href="g14_run@jlab.org">g14_run@jlab.org</a>><BR>
Sent: Saturday, November 4, 2017 12:00:03 PM<BR>
Subject: G14_run Digest, Vol 74, Issue 3<BR>
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Today's Topics:<BR>
<BR>
1. Re: Updated Analysis Note (Reinhard Schumacher)<BR>
2. Re: Updated Analysis Note (Nicholas Zachariou)<BR>
<BR>
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Message: 1<BR>
Date: Fri, 3 Nov 2017 22:19:24 -0400<BR>
From: Reinhard Schumacher <<a href="schumacher@cmu.edu">schumacher@cmu.edu</a>><BR>
To: <a href="g14_run@jlab.org">g14_run@jlab.org</a><BR>
Subject: Re: [G14_run] Updated Analysis Note<BR>
Message-ID: <<a href="a5780718-56ac-1dc0-44e8-6b991dbf849b@cmu.edu">a5780718-56ac-1dc0-44e8-6b991dbf849b@cmu.edu</a>><BR>
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Hi Nick,<BR>
<BR>
Indeed, noticeably improved.?? I recommend that you put the horizontal<BR>
error bars on Figs.? 29 - 32, too.? They are just as important there<BR>
since the model curves can vary a lot across one bin.<BR>
<BR>
Reinhard<BR>
<BR>
<BR>
On 11/3/2017 7:13 PM, Nicholas Zachariou wrote:<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> Dear all,<BR>
<BR>
I am attaching the updated note that incorporates and addresses all<BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> comments made. I have noticed that I have previously forgotten to<BR>
include the systematic uncertainty associated with the<BR>
photon-selection, and is now estimated and included.<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> I would like to thank again Shumacher for his time and valuable<BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> insight, and everybody for the comments and feedback. If there is no<BR>
other comments, I will be submitting the note early next week.<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
Best regards,<BR>
Nick<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
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Reinhard Schumacher Department of Physics, 5000 Forbes Ave.<BR>
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phone: 412-268-5177 web: www-meg.phys.cmu.edu/~schumach <<a href="http://www-meg.phys.cmu.edu/~schumach">http://www-meg.phys.cmu.edu/~schumach</a>> <BR>
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Message: 2<BR>
Date: Sat, 04 Nov 2017 07:10:14 +0000<BR>
From: Nicholas Zachariou <<a href="nicholas@jlab.org">nicholas@jlab.org</a>><BR>
To: Reinhard Schumacher <<a href="schumacher@cmu.edu">schumacher@cmu.edu</a>><BR>
Cc: G14 Run <<a href="g14_run@jlab.org">g14_run@jlab.org</a>><BR>
Subject: Re: [G14_run] Updated Analysis Note<BR>
Message-ID: <<a href="d21ed42f-6b13-482d-8c8b-4ea087ad31e1@jlab.org">d21ed42f-6b13-482d-8c8b-4ea087ad31e1@jlab.org</a>><BR>
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Hi Reinhard,<BR>
<BR>
The figures looked a bit busy when I did that (too many lines) and<BR>
thats why i left the x-uncertainties out in those, but its takes me 2<BR>
minutes to incorborate them. I think that will be more relevant when we<BR>
decide exactly how to present our results in the publication.<BR>
<BR>
In the meantime I was wondering if its OK with the group to share our<BR>
preliminary results with the theorists and see if we can get any<BR>
insights from them.<BR>
<BR>
Best regards,<BR>
Nick<BR>
<BR>
<BR>
On Nov 4, 2017, 02:19, at 02:19, Reinhard Schumacher<BR>
<<a href="schumacher@cmu.edu">schumacher@cmu.edu</a>> wrote:<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> Hi Nick,<BR>
<BR>
Indeed, noticeably improved.?? I recommend that you put the horizontal<BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> error bars on Figs.? 29 - 32, too.? They are just as important there<BR>
since the model curves can vary a lot across one bin.<BR>
<BR>
Reinhard<BR>
<BR>
<BR>
On 11/3/2017 7:13 PM, Nicholas Zachariou wrote:<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> Dear all,<BR>
<BR>
I am attaching the updated note that incorporates and addresses all<BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> comments made. I have noticed that I have previously forgotten to<BR>
include the systematic uncertainty associated with the<BR>
photon-selection, and is now estimated and included.<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> I would like to thank again Shumacher for his time and valuable<BR>
</SPAN></FONT></BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> insight, and everybody for the comments and feedback. If there is no<BR>
other comments, I will be submitting the note early next week.<BR>
</SPAN></FONT><BLOCKQUOTE><FONT FACE="Calibri, Verdana, Helvetica, Arial"><SPAN STYLE='font-size:11pt'> <BR>
Best regards,<BR>
Nick<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
<BR>
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