[d2n-analysis-talk] Dilution Factors

[Matthew R. Posik]

Hi Greg,

On Wed, Apr 20, 2011 at 8:56 PM, Gregg B. Franklin <gbfranklin at cmu.edu>wrote:

> Matt,
>   The plots you have are very interesting.  The dilution factor at low
> x is a much bigger effect than we were anticipating.  I think we should
> first try to make sure we agree on the dilution factor determined by the
> reverse polarity run at 4.7 GeV.  It would be useful to plot 1-D instead
> of D since D gets close to 1.0 through much of our range.  Lets make
> sure we agree on the runs, the cuts, etc.
>

I plotted 1-D. Again D is defined as:

    D = 1-(Q-/Q+)*(N+/N-),

    Q-, N- is the accumulated charge and total counts from the negative
polarity runs 2024-2195

   Q+, N+ is the accumulated charge and total counts from the positive
polarity runs 2199-2212

The plot pos_outrun_1mdilution.eps shows 1-D. Since the higher x bins are
near 0 here I also plotted it on log scale (pos_outrun_1mdilution_log.eps)

I also plotted 1-D' for the negative polarity runs 2024-2195 using
BB.optics.charge==-1 for electrons and BB.optics.charge==1 for positrons

Again here D' is defined as

 D' = 1 - N-/N+

where N- are the total counts with charge==-1
           N+ are the total counts with charge==1

You can see a plot of 1-D' pos_inrun_1mdilution.eps

>
> We also want to check the asymmetry, also.  If it is large, this is a
> big problem in addition to just "dilution factor".  We need to at least
> put a bound on the asymmetry.
>

I Computed the raw positron asymmetry from the positive polarity runs. I
will send that result out in a separate email.

>
>   For the 5-pass data, the following strategy might work if we have
> enough statistics.
>
> 1) Start with the 4.7 GeV data and determine the positrons (from reverse
> polarity running) normalize by charge as a 2-D function of momentum and
> scattering angle.  Call this 2D histogram 1.  It will have to be course
> binned.
>
> 2) Do the same for positrons determined from the negative (normal
> polarity) running at 4.7G.   In both cases, we should have mostly just
> positrons.   Call this histogram 2.
>

I will get started on getting these histograms.

>
> 3) Determine the ratio of Hisogram 2) over Histogram 1) bin by bin
> should give use the relative acceptance for positrons as a function of
> scattering angle and momentum.  (Our statistics will be poor at high x,
> but hopefully the positrons aren't a problem there.)
>
> I don't think positrons will be an issue here, looking at the dilution
factors that I  got using the two different methods, they seem to both agree
pretty well at large x and both say very few positrons at large x.


> 3) For the 5-pass data, make hisogram 3 with similar bins for positrons.
>  This will be for the normal polarity, which means the acceptance will
> be very different than for the real data.  However, you can use the
> ratios (bin by bin) determined in step 3 to correct for this.  The
> problem might be that the "4-pass" data may have low statistics in
> kinematics bins that become important at 5-pass.
>
> In the longer run, we can try to understand this ratio with Monte Carlo.
>  If there is a large asymmetry and therefore can depend on the target
> polarization direction, it will be harder.
>
> Regards,
> Gregg
>
>
>
> --
> Prof. Gregg B Franklin
> Head, Department of Physics
> Carnegie Mellon University
> phone: (412) 268-2743   fax: (412) 681-0648
> _______________________________________________
> d2n-analysis-talk mailing list
> d2n-analysis-talk at jlab.org
> https://mailman.jlab.org/mailman/listinfo/d2n-analysis-talk
>



-- 
Matthew Posik
Email: posik at temple.edu
Temple University Physics Dept.
Office: BA-319
Office #:  215-204-1331
WebSites:
Temple:
http://quarks.temple.edu/
d2n:
http://hallaweb.jlab.org/experiment/E06-014/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20110421/9ec9d464/attachment-0001.html 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pos_outrun_1mdilution.eps
Type: application/postscript
Size: 10318 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20110421/9ec9d464/attachment-0003.eps 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pos_outrun_1mdilution_log.eps
Type: application/postscript
Size: 10221 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20110421/9ec9d464/attachment-0004.eps 
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pos_inrun_1mdilution.eps
Type: application/postscript
Size: 11049 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/d2n-analysis-talk/attachments/20110421/9ec9d464/attachment-0005.eps