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Hi Michael<br>
Apologies if I have missed the point of the discussion. I think
the behaviour observed in your nice analysis is what would be
expected.<br>
The Q-factor explicitly requires inclusion of all variables that
will be used in further analysis, so in your case certainly phi must
be included in the nearest neighbours search. For other reactions
also involving fits to decay angles for example, these decay angles
must also be included in the nearest neighbour search.<br>
If this is not done then it is probably not actually the Q-factor
method that is being applied but just a single probabilistic weight
function for all events. So if the signal and background ratio
change as a function of the variable you are interested in, clearly
the single probabilistic weight function will not apply at all
values of the variable. Instead the Q-factor is equivalent to making
many probabilistic weight functions for events in very small bins of
phi so the signal/background is approximately constant for that bin.
This also has the implication that if the range of your phi bin for
N nearest neighbours is large (e.g. if you have low statistics, or
many variables) Q-factor will not work so well.<br>
Sorry if this adds to any confusion, but in short I agree with
your analysis.<br>
Cheers<br>
Derek <br>
<br>
<div class="moz-cite-prefix">On 11/08/16 23:38, Michael Dugger
wrote:<br>
</div>
<blockquote
cite="mid:Pine.LNX.4.64.1608111820190.10415@jlabl1.jlab.org"
type="cite">
<br>
Hi,
<br>
<br>
During our discussion today, regarding the
<br>
Q-factor dependence on azimuthal angle, it
<br>
became clear that I needed to have a better
<br>
explanation. I have created an example that
<br>
I hope illustrates the point I was trying
<br>
to make.
<br>
<br>
A simple Q-factor example can be found at
<br>
<br>
<a class="moz-txt-link-freetext" href="https://userweb.jlab.org/~dugger/omega/omega6.pdf">https://userweb.jlab.org/~dugger/omega/omega6.pdf</a>
<br>
<br>
Note: The 2nd slide is just a repeat of what
<br>
I had shown previously. The new information starts
<br>
on slide 3.
<br>
<br>
In addition, I have attached the plot
<br>
(allCos.png) that Barry requested (moment method
<br>
for integrated polar angle).
<br>
<br>
Take care,
<br>
Michael
<br>
<br>
<br>
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<br>
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