[d2n-analysis-talk] Positive Polarity GC/PR Calibration

[Brad Sawatzky]

On Fri, 15 Oct 2010, David Flay wrote:

> I wanted to finish off the GC/PR calibration, since I have only two
> kinematics to go -- p = 1.12 GeV (4-pass) and p = 1.34 GeV (5-pass).
> 
> The gas Cherenkov calibration went just fine -- the calibration done
> for negative polarity works on these positive polarity ones (the 1
> photoelectron peak shows up at 200 channels).  I have attached a

Glad to hear that.  Neither package "knows/cares" what the field
polarity is.  It would be very strange if the calibration changed
with the field setting (of course).

> Cherenkov sum plot for the p = 1.12 GeV kinematic.  It is odd how
> there is <no> main peak in this histogram -- the same is true for the
> p = 1.34 GeV case...

Presumably this is just a side effect of being dominated by the pi+,
with very few positrons (which really only come from pi0 -> e+, e-).  I
think pi+ rates at those momenta should be in the 10s of Hz (or less),
while positrons rates are several orders smaller than that.

> I was expecting something similar to happen on the pion rejector.
> However, when examining the ADCs (corrected variables) for the p =
> 1.12 GeV kinematic, I have <two> peaks (even with a cut requiring
> GC_sum==0), one being at ~45, and the other at 100.  I was
> anticipating that the \pi^{+} would fall in one peak, at around 100.
> Now, I have chained runs together to get decent statistics, but I
> don't think that's the issue here, as this also occurs for individual
> runs.  This effect is most visible in the second layer.  The same
> thing happens for p = 1.34 GeV.
> 
> I'm curious as to what that double-peak structure is -- it can't be
> e^{+} since I have a L.cer.asum_c==0 cut on these plots...

What does s2m-s1 (ie. beta) look like for the two peaks?  Perhaps one
peak is cosmics?

-- Brad

-- 
Brad Sawatzky, PhD <brads at jlab.org>  -<>-  Jefferson Lab / Hall C / C111
Ph: 757-269-5947  -<>-  Fax: 757-269-5235  -<>- Pager: brads-page at jlab.org
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