[Frost] tagger sag

[dugger at jlab.org]

Sungkyun,

I am sorry.

I did not understand what was shown.

At first glance, it looks like the tagger sag is correctly dealt with. The
error bars are still a bit large. If I read your CH2 (eloss corrected)
plot correctly, it looks like the energies are within +/- 0.5%. There is
not enough photon energy bins to see if there is the 3 bump structure.

If we assume that the tagger sag has been dealt with, then the next thing
is to find the momentum corrections.

I got an email from Brian Vernarsky today. He stated that he is ready to
start looking at the energy and momentum corrections for g9. He has his
code working for g1c. With any luck we should get some correction factors
for g9 soon.

I apologize for the confusion.

Sincerely,
Michael





> Hi Michael,
>
>> Unless the photon pulls are better than you have previously reported, the
>> energy differences shown can not be taken as accurate. This means that
I  do not know what to say regarding your most recent plots.
>
> I do not understand why you say about the photon pull with my
yesterday's
> plots.
> I do not use any kinematic fitting term in my yesterday's plots. I only
follow your suggestion to check if the tagger sag is correctly included
in g9a.
> Thus, I make histograms with [E_calculated - E_measured]/E_measured and
enough statistics to get
> the numbers to the 0.1 % level.
>
> My understanding is that the kinematic fitter need to have momentum as
the
> initial value and it correct momentum using energy conservation. In this
case, the initial energy is very important factor.
>
> Before kinematic fitting, the momentum can be corrected by using several
correction. now I used eloss correction and will use momentum correction
for g9a.
>
> Unfortunately, after applying the eloss correction, the pull
distribution
> in butanol target is still very bad.
> I am not sure if our eloss package correct momentum and to check the
effect of our eloss package, I make the plot with the ratio of the
calculated photon E to measured photon E.
>
> If in my yesterday' plot, we can not check the problem of the tagger
sag,
> what do I make to check them?
> It is also important to check if we have the problem of the tagger sag now.
> I think in the current status, we can not use the result of the
kinematic
> fitting.
>
> How do you think that I add the code to correct the tagger sag from g8b
in
> my analysis code and I make some plots to compare?
>
> Sung
> Florida State University
>
>> Chuck had stated that the pull parameters are going to give you more
meaningful information than the corrected energy. He should know. Why
don't you do as he suggested, and show the center of the photon pulls
as a
>> function of photon energy?
>> Of course you are free to feel confident in the corrected values of
thephoton energy given by your kinematic fitter. It is up to you to
find out
>> how best to make the photon pull parameters more reasonable. I would
concentrate on the easiest thing first: Make the Carbon and CH2
targetshave reasonable pulls, and then work on the Butanol target. That
is just
>> me. It is your analysis.
>> Happy hunting.
>> Best wishes,
>> Michael
>> > Hi Dugger,
>> >
>> > I have made more updated histograms.
>> > The y-axis value has [E_calculated - E_measured] / [E_measured] The
x-axis has [E_measured] or Z-vertex.
>> > You can check my results in the following web:
>> >
>> >    http://www.jlab.org/Hall-B/secure/g9/sungkyun/6-14-10.html
>> >
>> > I am sure that after applying the recent updated eloss
>> correction, the
>> > ratio of {E(cal. photon) - E(cal. photon)} to E(cal. photon) has
>> been> located near zero more. I think the current eloss is improved more.>
>> > I do not know about the tagger sag. After eloss correction, there
>> are> still structure. that is, In the low energy, measured photon
energy is
>> > bigger than calculated photon energy. However, the difference is
>> very> small when we compare them with the histogram which are made
before eloss.
>> > Do you think the reason of this difference is the tagger sag?
>> >
>> > Sung
>> >
>> > Florida State University
>> >
>> >
>> >
>> >
>> > ----- Original Message -----
>> > From: Michael Dugger <dugger at jlab.org>
>> > Date: Wednesday, June 9, 2010 4:34 pm
>> > Subject: Re: [Frost] tagger sag
>> > To: Sungkyun Park <sp06k at fsu.edu>
>> > Cc: frost at jlab.org
>> >
>> >>
>> >> Sung,
>> >>
>> >> I really hate to be a bother. From what I can tell, the plots you
show are
>> >> from the kinematic fitter. The FSU kinematic fitter showed the exact
same
>> >> kind of agreement for g8b. I do not know why. There were many
discussions regarding this. Please see
>> >> http://www.jlab.org/~dugger/tmp/meanValues_048326.A10.gif (this plot
goes
>> >> along with the email I got from Charles Hanretty shown at the bottom of
>> >> this email). Charles and I had the exact same conversations
>> >> regarding the
>> >> tagger sag for g8b.
>> >>
>> >> The pull parameters for the photon energy are a much better gauge of
how
>> >> well the measured photon energy compares to the calculated when using a
>> >> kinematic fitter. A kinematic fitter can not be relied upon to give
accurate results when the pulls are not close to optimal. This
appears to
>> >> very much the case for the calculated photon energy using the FSU
kinematic fitter for g8b (and probably for g9a as well).
>> >>
>> >> You can see the difference in the pull parameters before and after the
>> >> tagger sag correction for g8b data in Fig. 7 on page 8 of
>> >> http://www1.jlab.org/ul/Physics/Hall-B/clas/public/2009-030.pdf
>> >>
>> >> Your photon pulls shown on your web page at:
>> >> http://www.jlab.org/Hall-B/secure/g9/sungkyun/6-1-10.html
>> >> Give the following parameters:
>> >>
>> >> Carbon->
>> >> mean 0.122
>> >> sigma 1.124
>> >>
>> >> CH2->
>> >> mean 0.251
>> >> sigma 1.235
>> >>
>> >> For Chuck using g8b data:
>> >>
>> >> Before tagger sag correction->
>> >> mean 0.3027
>> >> sigma 1.219
>> >>
>> >> After tagger sag correction->
>> >> mean 0.0049
>> >> sigma 1.040
>> >>
>> >> At first glance, it looks entirely reasonable to suspect that you
have the
>> >> same sort of photon energy problems that Chuck had.
>> >>
>> >> I also want to make it clear that the sag correction was supposed to be
>> >> included in the g8b data and it was never determined what went
wrong. Why
>> >> should we assume that the tagger sag is fixed when it has not been
verified?
>> >>
>> >> One more thing that might be of interest: It appears that the
[E_calculated - E_measured] is nearly perfect for the comparisons
done by the kinematic fitter. However, it would be very surprising
to get
>> >> this same type of result from your most recent study at:
>> >> http://www.jlab.org/Hall-B/secure/g9/sungkyun/6-9-10.html
>> >>
>> >> I only propose that you find out [E_calculated -
>> >> E_measured]/E_measured using your most current study (without kinematic
>> >> fitter) and include enough statistics to get the numbers to the 0.1%
>> >> level. This would serve as a way to verify that the tagger sag is
correctly included in g9a.
>> >>
>> >> No matter what, you are going to have to get your photon pulls to be
much
>> >> better before you can reliably use the kinematic fitter in your
analysis.
>> >> That is the price you pay for using such a powerful technique.
>> >>
>> >>
>> >> ************************
>> >> Date: Wed, 19 Aug 2009 15:18:41 -0400 (EDT)
>> >> From: Charles Hanretty <hanretty at hadron.physics.fsu.edu>
>> >> To: Michael Dugger <dugger at jlab.org>
>> >> Subject: Re: E(true) and E(meas)
>> >> Parts/Attachments:
>> >>    1 Shown    161 lines  Text
>> >>    2   OK      12 KB     Image
>> >> ----------------------------------------
>> >>
>> >> Mike,
>> >>    Attached is a plot I have of the mean values generated from
>> >> just 1
>> >> 1.3GeV file
>> >> (cooked_048326.A10.B00).  I fit each slice of the
>> >> (Etrue/Emeas)vEmeas plot
>> >> by using the function
>> >> TH2::FitSlicesY (168 slices).  Looking at this, one could see the
similarity between this plot and
>> >> the one you showed at the meeting.  I've made this final plot
(Etrue-Emeas v Emeas) but it does not look how I expect it to or
want it
>> >> to
>> >> so I'm trying to figure out if I made an error somewhere.  One thing to
>> >> note
>> >> is that the differences between Etrue and Emeas (for me) seem to be
smaller
>> >> than the differences you are dealing with.  This might flatten out
some of
>> >> the bumps we're looking
>> >> for.  For example, your Etrue/Emeas v Emeas plot has a
>> >> y-range of 0.95-1.05.  I started off with this range but had a lot of
>> >> empty
>> >> space and therefore have changed my y-range to 0.998-1.002.
>> >> Anyway, this
>> >> is an update; there is
>> >> still work to be done.
>> >>
>> >> -Chuck
>> >> *************************************88
>> >>
>> >> -Michael
>> >>
>> >>
>> >> On Wed, 9 Jun 2010, Sungkyun Park wrote:
>> >>
>> >> > Hi Michael,
>> >> >
>> >> > My understanding is that we do not worry about the problem of the
>> >> tagger sag in FROST data.
>> >> > When we make the cooking file, that problem is corrected.
>> >> >
>> >> > I make a same plot made at g8b.
>> >> > The first plot is about E-id vs E{true photon beam} - E{measured
>> >> photon beam}
>> >> > The second plot is about E{measured photon beam} vs E{true photon
>> >> beam} - E{measured photon beam}
>> >> >
>> >> > These plots are made in topology #gamma p -> p #pi+ #pi- (all
>> >> detected) and the updated eloss correction is applied.
>> >> > E{measured photon beam} is the initial photon energy.
>> >> > E{true photon beam} is the photon energy after kinematic fitting.
I used 0.05 as the confidence level cut. I used only a run 55570
>> >> in period 3. The electron beam energy of period 3 is 1.645 GeV. So
The energy range of E{measured photon beam} is from 0.33 GeV to 1.56
GeV.
>> >> > When we compare plots in CLAS-NOTE with plots attached with this
>> >> email, FROST data do not have any problem of the tagger sag.
>> >> >
>> >> > Sung
>> >> > Florida State University
>> >> >
>> >> >
>> >> > ----- Original Message -----
>> >> > From: Michael Dugger <dugger at jlab.org>
>> >> > Date: Wednesday, June 9, 2010 1:04
>> >> > Subject: [Frost] tagger sag
>> >> > To: frost at jlab.org
>> >> >
>> >> >>
>> >> >> Hi,
>> >> >>
>> >> >> I know that the study Sungkyun performed was to help verify the
eloss
>> >> >> momentum corrections, and I think that this is a reasonable
>> way to
>> >> >> look at
>> >> >> his study. However, this sort of study is also very useful in
determining
>> >> >> the tagger sag. Since the eloss correction is not as
>> pronounced for
>> >> >> the
>> >> >> Carbon and CH2 targets, these targets can give us a good
>> picture on
>> >> >> the
>> >> >> tagger sag situation.
>> >> >>
>> >> >> If you look at the CLAS note:
>> >> >> http://www1.jlab.org/ul/Physics/Hall-B/clas/public/2009-030.pdf
>> >> >>
>> >> >> Fig. 5 on page 6 shows the tagger sag correction to be on the
>> order>> >> of
>> >> >> 0.5% for g1c data. For g8b data, the sag correction was
>> between 0.2
>> >> >> to
>> >> >> 1.0% (Fig. 6 page 7). This means that we need to look for energy
effects
>> >> >> on the order of 0.1% to be sure that the tagger sag is not an
>> >> issue.>>
>> >> >> For g8b it was found that the tagger sag correction was
>> important>> >> in
>> >> >> obtaining reasonable pulls for the FSU kinematic fitter (see
>> table>> >> 1 on
>> >> >> page 7).
>> >> >>
>> >> >> One way to get a better look at the energy study is to use:
[E_calculated - E_measured]/E_measured
>> >> >> instead of
>> >> >> E_calculated/E_measured.
>> >> >>
>> >> >> Since Mike Williams used this sort of parametrization for g1c
>> (and>> >> I
>> >> >> did the same for g8b), we can more easily compare results
>> between>> >> the
>> >> >> different run periods to see if the shape of the energy
>> correction>> >> distributions look similar. The tagger sag has a
"signature" three
>> >> >> bump
>> >> >> pattern that should be clearly visible once we get to the 0.1%
>> >> level.>>
>> >> >> -Michael
>> >> >> _______________________________________________
>> >> >> Frost mailing list
>> >> >> Frost at jlab.org
>> >> >> https://mailman.jlab.org/mailman/listinfo/frost
>> >> >>
>> >> >
>> >>
>> >
>