<br><br><div class="gmail_quote">On Tue, Sep 7, 2010 at 12:35 PM, Brad Sawatzky <<a href="mailto:brads@jlab.org">brads@jlab.org</a>> wrote:<br><blockquote class="gmail_quote">
<div>On Fri, 03 Sep 2010, David Flay wrote:<br>
<br>
> I have uploaded to the Wiki my calculation for the projected<br>
> statistical error on A_1^n, along with a plot containing the current<br>
> world data on A_1^n, with the statistical errors calculated at 5-pass<br>
> superimposed for comparison. I have also included Matt's calculations<br>
> of the A_{\perp} statistical error for the same 5-pass data.<br>
<br>
</div>A few questions/comments:<br>
<br>
- In the caption for Table 1, say something like:<br>
... using the BigBite data from runs 2022---2054 (E_beam = 4.73 GeV/c.)<br>
Make similar additions in the other Table captions.<br>
<br>
- (Minor typesetting quibble) There is no space between the number and<br>
the dash when you list a range. The LaTeX code for a range should be:<br>
2022--2054<br>
not<br>
2022 - 2054, nor 2022 -- 2054, nor 2022-2054.<br>
The double dashes generate an en-dash.<br>
<br>
Just FWIW, here is a good page of general typesetting and LaTeX tips:<br>
<a href="http://web.science.mq.edu.au/%7Erdale/resources/writingnotes/latexstyle.html">http://web.science.mq.edu.au/~rdale/resources/writingnotes/latexstyle.html</a><br>
Good things to keep in mind as you draft your thesis.<br></blockquote><div><br>Thanks! <br> <br></div><blockquote class="gmail_quote">
- Have the 3 days of unpolarized-beam running been excluded from this<br>
analysis?<br></blockquote><div><br>Yes -- I took the appropriate runs from Matt's table: <a href="https://hallaweb.jlab.org/wiki/index.php/Big_Bite_Kinematics_Run_Break_Down">https://hallaweb.jlab.org/wiki/index.php/Big_Bite_Kinematics_Run_Break_Down</a><br>
<br>(P.S. -- is there a direct link to this on the front page of the Wiki? I couldn't find it... so I put a link here: <a href="https://hallaweb.jlab.org/wiki/index.php/Analysis_resources_for_d2n#Preliminary_Production_Run_List">https://hallaweb.jlab.org/wiki/index.php/Analysis_resources_for_d2n#Preliminary_Production_Run_List</a>)<br>
<br><br></div><blockquote class="gmail_quote">
- Why do we have so much parallel data at p=0.80 vs. the other points<br>
(Table 1)?<br>
<br>
- I don't understand the "N_eff" quantity. For the 4-pass data, N_eff<br>
is less than N_p, but for the 5-pass data N_eff > N_p. I've read the<br>
description on p.2 a couple of times and still don't get it (maybe I<br>
just need more coffee or something...)<br></blockquote><div><br>Because: <br> <br>A) I made a mistake in my code that calculates the values for the 4-pass data -- I corrected this, now the numbers make sense... see <br>
<br>B) The idea behind "N_eff" is to "scale up" the percentage of events remaining from the sample run used in the analysis to the total data taken at each beam pass. <br><br></div><blockquote class="gmail_quote">
Could you pick on momentum bin (say 1.20 GeV/c) and be a little more<br>
explicit on how you arrive at N_p, N_cut, and N_eff?<br></blockquote><div><br>for p = 1.20 GeV/c at E_beam = 5.89 GeV , we use the momentum cut: 1.165 < BB.tr.p[0] < 1.235 (in accordance with the formula in the note). <br>
<br>Using this cut only, we see how many events remain for the (sample) run 2060. So, we have:<br><br>N_raw = 4681052 (total number of events recorded for run 2060).<br><br>N_p = 30386 (the number of events that survive a momentum cut, as specified above). <br>
<br>Now, we then apply <all> good electron cuts. This includes:<br><br> 1. GC mirror cuts, ADC, and TDC cuts<br> 2. Various tracking cuts<br> 3. Preshower and Shower cuts <br> 4. Momentum cut (from above)<br>
<br>We then see how many events survive this cut. We call this N_cut:<br><br>N_cut = 4372 <br><br>Now, the number of events recorded for parallel running (runs 1530--1553 and 1702--1719) is:<br><br>N_T = 214350416<br><br>
Now, we determine N_eff --- we see what percentage of events survive all cuts, as compared to the original number of events:<br><br>N_eff = (N_cut/N_p)*(N_p/N_raw)*N_T = (N_cut/N_raw)*N_T <br></div><div><br>Here's the tricky part --- I considered two different ideas:<br>
<br>The first was N_eff = (N_cut/N_p)*N_T. [option 1]<br><br>The second was: <br><br>N_eff = (N_cut/N_raw)*N_T, [option 2] <br><br>and is the one I used in the calculations in the note. <br><br>My reasoning behind the first was: shouldn't the percentage of events that survive the good electron cuts be determined from sample events that <satisfy> the momentum cut --- since that sample of events I am considering to be from the momentum bin of interest? <br>
<br>But then I thought about how we should properly 'scale' the number of events that survive the cuts to the full statistics we took. Now, it's clear from the first form that N_eff seemingly does not depend upon N_raw (the number of events we started out with in the first place) --- it's indirect at best. Therefore, I thought that N_eff should reflect this -- that is, it should be a scale factor multiplied by the total statistics taken during the parallel running. This results in:<br>
<br>
N_eff = (N_cut/N_raw)*N_T [option 2] <br><br>This is an estimate of the percentage of (total) events that would survive all the cuts --- that is, momentum plus good electron cuts --- because the only difference between doing this calculation for one run (2060) and all the runs listed (runs 1530--1553 and 1702--1719), is that there's more events. On average, I would expect the behavior of the cuts to be the same if we just added more and more events to the study. <br>
<br>Further reasoning behind using [option 2]: <br><br>N_T in [option 1] is <not> the total number of events for given momentum bin --- N_T is just the total number of events for the appropriate runs. I think it would be correct if I determined the total number of events (summed over all valid runs) for each momentum bin for N_T. [option 2] does not have this issue -- equation is: (ratio of events that pass cuts/total number of events)*(total number of events for parallel running). <br>
<br>Please see the corrected note (corrected errors at 4-pass):<br><br><a href="http://www.jlab.org/%7Eflay/thesis/A1_error/A1_stat_error_note_v2.pdf">http://www.jlab.org/~flay/thesis/A1_error/A1_stat_error_note_v2.pdf</a><br>
<br><br clear="all"><br>-- <br>-----------------------------------------------------------<br>David Flay<br>Physics Department<br>Temple University<br>Philadelphia, PA 19122 <br><br>office: Barton Hall, BA319<br>phone: (215) 204-1331<br>
<br>e-mail: <a href="mailto:flay@jlab.org">flay@jlab.org</a> <br> <a href="mailto:flay@temple.edu">flay@temple.edu</a><br><br>website: <a href="http://www.jlab.org/%7Eflay">http://www.jlab.org/~flay</a><br>
<a href="http://quarks.temple.edu">http://quarks.temple.edu</a><br>-----------------------------------------------------------<br><br><br>
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