[Clas12_verystrange] slides and meeting

[Michael Dugger]

Hi,

Below is a sample response to the PID question I was asked about during 
the meeting:

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Comment:

* Fig.21 shows all particles of the events at the same time but
   what is the probability that one of the particles in an event
   has a momentum above 2 GeV (and is therefore misidentified)?

Response:

We have determined that the contamination in the kaon sample, for momentum 
less than 2.5 GeV, is typically less than 1%. You can find slides 
discussing this at

http://www.public.asu.edu/~dugger/veryStrange/pidStudy1b.pdf
and
http://www.public.asu.edu/~dugger/veryStrange/pidStudy2.pdf

For the Omega reaction we expect:
* 70% of K+ have momentum less than 2 GeV
* 83% of K+ have momentum less than 2.5 GeV
* 91% of K- have momentum less than 2 GeV
* 98% of K- have momentum less than 2.5 GeV

As can be seen, pushing the upper range in momentum of "good" kaons from 
2.0 to 2.5 GeV, the fraction of K+ within the "good" range is much larger.

The contamination study only relied on a rudimentary PID scheme, and it is 
expected that more sophisticated methods of determining PID (e.g. Boosted 
Decision Trees) will help in reducing the kaon sample contamination. 
Moreover, when the entire reaction is taken into account, the requirement 
of displaced vertices is very helpful in creating a more purified kaon 
sample.

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Feel free to change the wording.

Take care,
Michael