Re: comment on simulation section

[Elton Smith <elton@jlab.org>]

HI Matt and Mihajlo,

I read the section on simulation and reconstruction and I have some
comments (the version I refer to is Jan 29).

page 2, Figure 1 caption, first line, is this what you mean?
'related to the actual experiment' -> raw data and low-level calibrations
that are bypassed in the MC event generator by directly producing hits in
the detector.


page 3, Section 2:

The description of hit generation (top of page 3 for fcal and under 2.2
for Bcal), at least I think that is what is described for what information
is recorded is somewhat confusing. Assuming this is the generation of
hits, I would state this explicitly: for the fcal each block (with energy
above some threshold?) is recorded. I assume for the bcal, for each
readout channel, one saves the summed energy, z-position, average time?
The statement 'time of all energy deposits' is unclear unless one saves
the energy of all particles in the shower?

To clarify, I would simply point to the middle of the flow chart (page 2)
and specify what information is stored for each hit during the simulation.


page 3, section 2.2 BCAL, second line
'active BCAL region' -> scintillating fibers

page 4, section 2.3, first line - not a sentence
-> We believe the dominant contributions ..... However, there are
additional...

page 5, Section 3 middle paragraph
...match THE generated photon momentum...

page 5, 3.1 bottom line
...position ARE corrected FOR shower depth and non-linear effects.

page 8, line before eq 9
Do you mean 'position of the photon AT THE INNER SURFACE OF THE BCAL...'

page 8, eq 9.
I do not understand what the vectors are, and 'some parameter s' is too
vague. This could be explained more clearly.

page 9, next to bottom line, question
'...position resolution of a couple of millimeters...'
Given a speed of 17 cm/ns, a sigma=100 ps corresponds to 1.7 cm, so I
expect resolutions of a couple of centimeters. Since the text is
consistent with figure 8, I am confused as to why the resolution is so
good.

page 11, bottom line, vertex errors
Assuming the vertex position error is the 'size of the target (30cm)' for
reconstruction seems to be very pessimistic. Does this uncertainty in the
vertex position influence all the invariant mass plots? Should it be
updated (even artificially) by assuming a charged particle z-position
resolutions?

page 12, last paragraph middle (figure 10)
'The plot on the right shows the efficiency in a window..." Do you mean
the left plot?

page 12, footnote, lacks final period.

page 14, footnote, lacks final period.

page 15, figure 11, question
Do we understand why the resolutions in the FCAL are much better than the
resolutions in the BCAL? In the introduction Alex plots pi0 and eta widths
and there seems to be little difference between FCAL and BCAL. What is
different? If we know this we should add a note to the text. (Could it be
the vertex resolution? see above).

page 18, section 4.2.1 first paragraph last line
two-photon decayS of the eta.

page 19, second paragraph, midle
The expected hadronic background in this channel... (remove IS)

page 21, figure caption / first paragraph
It might be useful to specify how much running time 100,000 events
corresponds to.

page 23, figure 20 (right)
It is hard to see the data symbols. If I read them correctly there seems
to be substantial false P-wave found for masses around 0.9 GeV (about 20%)
which seems to be quite large. Symbols in different colors would help see
what is plotted, but there should be a comment on the amount of  false
resonant P-wave.

Cheers, Elton.






Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave
Suite # 16
Newport News, VA 23606
elton@jlab.org
(757) 269-7625
(757) 269-6331 fax

On Thu, 7 Feb 2008, Alex Dzierba wrote:

> Hi Elton
>
> When you send those comments to Matt and Mihajlo about the
> simulations section please cc to me as well.  I can start taking
> care of the more straight-forward corrections/additions.
>
> Thanks much
> Alex
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Alex R. Dzierba
> Chancellor's Professor of Physics (Emeritus)
> Department of Physics / Indiana U / Bloomington IN 47405 / 812-855-9421
> JLab Visiting Fellow
> Jefferson Lab / 12000 Jefferson Ave / Newport News, VA 23606 / 757-269-7577
> Home Phone: 812-825-4063  Cell:  812-327-1881  Fax: 866-541-1263
> http://www.dzre.com/alex
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>