[d2n-analysis-talk] H2 cross section

[Brad Sawatzky]

On Wed, 21 Apr 2010, posik at jlab.org wrote:

> So I am looking into the BBNormAna stuff now. In the mean time last
> night I went to look at how to get the other parameters that I will
> need to compute the H2 cross section.
> 
> The first thing that I want to comment on is the shape of L.tr.tg_th,
> there looks to be a dip in the center of the distribution (the middle
> plot in the fig attached). Is this normal?, Or could something maybe
> be blocking the angle?

I commented on this and a couple other things in an earlier note: 'Re:
BB/LHRS tracks' on 08:55 2010-04-20.  It looked strange to me too --
check with Zein-Eddine and see if it makes sense to him.

> With that said, then next thing I want to do is calculate the density
> of our target. To do this I use the Ideal gas law and have
[ . . . ]

Check with Lamiaa for the target density stuff.  She should be able to
point you to the correct calibrations and formulae, or put you in touch
with one of the target experts.  (She may have even done some of the
work already.)

We had a couple of independent pressure readings.  I think they were all
gauge pressure, but I'm not certain.  There was also an issue with the
gauges' "zero" set point drifting over time...

I did a quick search and found this talk by Yi from last month:
  https://hallaweb.jlab.org/dvcslog//transversity/317
And another document that might be useful:
  https://hallaweb.jlab.org/dvcslog//transversity/351
They are worth looking at for procedure and insight into the issues
found during the Transversity analysis.

> The next thing that shows up in the cross-section is the acceptance of
> the LHRS which consists of 3 parameters (d_ang,d_z and d_E). In all
> papers that I have read they calculate these quantities using Monte
> Carlo simulation.
> I do not have a Monte Carlo set up to simulate the angular acceptance.
> I spoke to Huan and he had told me that there is an acceptance problem
> with his Monte-Carlo acceptance. But he had told me to I could make
> acceptance cuts and just assume the angular acceptance is 1.

The phrase "assume the angular acceptance is 1" doesn't help much...
"1" what?  (Do you mean a some sort of correction factor?)

We're looking for a rough check here.  The nominal acceptance defined by
the floor angle, P0 setting, and existing HRS calibrations should be
fine.  Run the details by Zein-Eddine if you run into a snag.

-- 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
The most exciting phrase to hear in science, the one that heralds new
  discoveries, is not "Eureka!" but "That's funny..."   -- Isaac Asimov