[Frost] [EXTERNAL] Re: Follow up of last FROST meeting

[Michael Dugger]

Chan,

It is probably a good idea to try and keep the low momentum events, but I
would start out by removing them. Once you feel like you have everything
else under control, then you add in the p < 400 MeV/c events.

You can see if the momentum cut makes the pi0 mass closer to the nominal
value. Essentially, you just recreate slides 2 and 6 from your December 18
update:

https://clasweb.jlab.org/rungroups/g9/wiki/images/9/94/FROST_2019_12_18.pdf

Note: On slide 2 you have pre-ELOSS mass of pi0 = 196 MeV and post-ELOSS
mass of pi0 = 125 MeV. BUT on slide 6 you have post-ELOSS mass of pi0 =
134 MeV!! How did that happen? Then after ELOSS + momentum correction the
pi0 mass = 89 MeV. You want to get that all straightened out with the p >
400 MeV/c events. You mass of the pi0 after the ELOSS and momentum
corrections should be the correct value. The momentum correction is
designed to bring the pi0 mass to the correct value.

Take care,
Michael

> Hello Michael,
>
> Yes, I now understand what you are saying about the momentum acceptance
> varying rapidly between 300 and 400 MeV around scattering angle of 35deg.
>
> Would it be a bad idea to apply different low momentum cuts for particles
> under 35deg and above 35deg? So, 400MeV for particles with angle < 35deg
> and 300MeV for particles with angle >35deg.
> Because for higher energy photon events (photon energy > 1 GeV), it looks
> like there are lots of events in p = [350, 400] MeV region.
>
> Thank you,
> Chan
>
>
> On Tue, Dec 24, 2019 at 3:50 AM Michael Dugger <dugger at jlab.org> wrote:
>
>> Chan,
>>
>> For these sorts of plots it is interesting to make an additional MM^2
>> cut.
>> If you make a missing mass cut near the mass of the pion, you restrict
>> the
>> events to have the kinematics of
>>
>> gamma p -> p pi0 .
>>
>> As it currently stands, you are showing the theta versus momentum
>> distribution for all possible reactions. This is not a bad thing and the
>> plots have interesting features.
>>
>> The depletion stripes are probably bad time-of-flight paddles. You can
>> see
>> from the depletion stripes how the magnetic field is bending the path of
>> the charged particles as a function of momentum.
>>
>> The enhancement stripes are probably from the reaction gamma p -> p pi0
>> (compare to https://userweb.jlab.org/~dugger/pi0PphaseSpacePlotNew.png
>> ).
>>
>> You can clearly see the acceptance in polar angle and momentum. For
>> angle
>> above 35 degrees, it looks like the momentum acceptance is rapidly
>> changing between 300 and 400 MeV/c. This is probably the clearest
>> evidence
>> that a cut at 400 MeV/c is appropriate. For angles below ~35 degrees the
>> momentum acceptance issue is being caused by a bad time-of-flight
>> paddle.
>>
>> Take care,
>> Michael
>>
>> > Hello All,
>> >
>> > Here is a plot of momentum vs lab angle in bins of photon energies.
>> >
>> https://clasweb.jlab.org/rungroups/g9/wiki/images/2/2e/Low_mome_select_p_abs_theta.png
>> >
>> > Thank you,
>> > Chan
>> >
>> > On Mon, Dec 23, 2019 at 3:47 PM Chan Kim <kimchanwook at gwmail.gwu.edu>
>> > wrote:
>> >
>> >> Hello Michael,
>> >>
>> >> Thank you for your suggestion! I should have been more clear about
>> the
>> >> plots. The mmsq distribution I sent out yesterday was prior to any
>> event
>> >> selections.
>> >>
>> >> I have two quick questions..
>> >> 1. For momentum ranges of [0.31, 0.39] GeV, the mmsq distribution
>> (ones
>> >> I
>> >> sent yesterday) look like a gaussian distribution centered near 0,
>> plus
>> >> a
>> >> bump at 1GeV. Are these events bad because of these bumps at 1GeV?
>> >>
>> >> 2. Are events with backward scattering angles not good because they
>> >> don't
>> >> have information from DC?? since the drift chamber only covers from
>> 8deg
>> >> to
>> >> 142deg???
>> >>
>> >> Regards,
>> >> Chan
>> >>
>> >> On Mon, Dec 23, 2019 at 3:33 PM Michael Dugger <dugger at jlab.org>
>> wrote:
>> >>
>> >>> Hi,
>> >>>
>> >>> The last plot was for pion lab-momentum and lab-angles and the
>> >>> center-of-mass angle definitions were also messed up :(
>> >>>
>> >>> I have a new plot at
>> >>>
>> >>> https://userweb.jlab.org/~dugger/pi0PphaseSpacePlotNew.png
>> >>>
>> >>> The above plot shows that the momentum values below 400 MeV ARE
>> >>> important
>> >>> for MANY kinematic bins.
>> >>>
>> >>> However, even with the knowledge that we would be killing a bunch of
>> >>> bins,
>> >>> we may have to remove events with momentum below 400 MeV due to our
>> >>> possible inability to reconstruct the missing pi0 at low momentum.
>> >>>
>> >>> Sorry about any confusion my previous plot may have caused.
>> >>>
>> >>> Take care,
>> >>> Michael
>> >>>
>> >>>
>> >>> > Eugene,
>> >>> >
>> >>> > Thanks for catching that. I think I have pion angles instead of
>> >>> proton.
>> >>> >
>> >>> > I am going to back over the code to fix this.
>> >>> >
>> >>> > Take care,
>> >>> > Michael
>> >>> >
>> >>> >> Mike,
>> >>> >>
>> >>> >> The vertical axis can't be right. The proton can't go backwards
>> in
>> >>> the
>> >>> >> lab
>> >>> >> system
>> >>> >>
>> >>> >> -Eugene
>> >>> >>
>> >>> >>> -----Original Message-----
>> >>> >>> From: Frost <frost-bounces at jlab.org> On Behalf Of Michael Dugger
>> >>> >>> Sent: Monday, December 23, 2019 14:07
>> >>> >>> To: Stuart Fegan <s.fegan.glasgow at gmail.com>
>> >>> >>> Cc: frost at jlab.org
>> >>> >>> Subject: Re: [Frost] [EXTERNAL] Re: Follow up of last FROST
>> meeting
>> >>> >>>
>> >>> >>> Hi,
>> >>> >>>
>> >>> >>> Chan is just trying to answer questions raised about a possible
>> >>> >>> momentum
>> >>> >>> cut. I suggested that he look at where his events are in terms
>> of
>> >>> >>> kinematic
>> >>> >>> bins he will report on. My idea was to see if pushing up the
>> >>> momentum
>> >>> >>> cut
>> >>> >>> to perhaps 400 MeV would cause any issues within his kinematic
>> >>> binning.
>> >>> >>>
>> >>> >>> I just made a plot that can be found at
>> >>> >>>
>> >>> >>> https://userweb.jlab.org/~dugger/pi0PphaseSpacePlot.png
>> >>> >>>
>> >>> >>> that shows the lab angle versus lab momentum for protons coming
>> >>> from
>> >>> >>> the
>> >>> >>> reaction gamma p -> p pi0. The black curves are for constant
>> photon
>> >>> >>> energy
>> >>> >>> and the blue curves are for constant proton center-of-mass
>> cosine
>> >>> >>> values.
>> >>> >>>
>> >>> >>> The above plot would have to be verified but it looks like there
>> is
>> >>> no
>> >>> >>> need to
>> >>> >>> worry about low momentum protons.
>> >>> >>>
>> >>> >>> The idea I had was for Chan to produce this type of information
>> >>> using
>> >>> >>> real
>> >>> >>> data, but I did a poor job of explaining what I meant.
>> >>> >>>
>> >>> >>> I was trying to make life easier, but perhaps did not accomplish
>> >>> that
>> >>> >>> :(
>> >>> >>>
>> >>> >>> Take care,
>> >>> >>> Michael
>> >>> >>>
>> >>> >>> > Hi Chan,
>> >>> >>> >
>> >>> >>> > I'm going to chuck my two cents in, and reply to the FROST
>> list,
>> >>> >>> > because I missed the meeting last week.  Given the pion
>> is
>> >>> >>> > reconstructed from the proton missing mass, what's the
>> motivation
>> >>> for
>> >>> >>> > looking at proton momenta below the threshold where it can
>> >>> reliably
>> >>> >>> > reconstructed in CLAS as a proton?  Is this to tune the
>> cut,
>> >>> perform
>> >>> >>> > systematic studies, or is there a physics motivation here that
>> >>> I'm
>> >>> >>> missing?
>> >>> >>> >
>> >>> >>> > Cheers,
>> >>> >>> >
>> >>> >>> > Stuart
>> >>> >>> >
>> >>> >>> > On 23/12/2019 11:47, Michael Dugger wrote:
>> >>> >>> >> Chan,
>> >>> >>> >>
>> >>> >>> >> It is a bit of a data dump.
>> >>> >>> >>
>> >>> >>> >> What is your binning going to by for the analysis? Are you
>> >>> really
>> >>> >>> >> going to report values for E_gamma near 400 MeV?
>> >>> >>> >>
>> >>> >>> >> On slide 3 you show MM^2 and state that MM^2 for p < 280
>> MeV/c
>> >>> don't
>> >>> >>> >> look like the others. I'm not convinced that you can say much
>> >>> about
>> >>> >>> >> the MM^2 shown above p = 280 MeV/c.
>> >>> >>> >>
>> >>> >>> >> For your previous presentation:
>> >>> >>> >>
>> >>> >>> >>
>> >>> >>>
>> https://clasweb.jlab.org/rungroups/g9/wiki/images/9/94/FROST_2019_12_
>> >>> >>> >> 18.pdf
>> >>> >>> >>
>> >>> >>> >> on slide 2 you had a nice fit to the MM^2 distribution where
>> you
>> >>> >>> >> pulled off a pi0 mass. Are you able to do that for the low
>> >>> momentum?
>> >>> >>> >> Is it possible that you can not pull out any pi0 from the low
>> >>> >>> >> momentum data? I just do not see any pi0. Am I missing
>> >>> something?
>> >>> >>> >>
>> >>> >>> >> Take care,
>> >>> >>> >> Michael
>> >>> >>> >>
>> >>> >>> >>>
>> >>> >>> >>>
>> >>> >>> >>> Dear FROST run group,
>> >>> >>> >>>
>> >>> >>> >>> Hello, below is a link to my slides for follow up of last
>> FROST
>> >>> >>> >>> meeting(12/19):
>> >>> >>> >>>
>> >>> >>>
>> https://clasweb.jlab.org/rungroups/g9/wiki/images/e/ed/FROST_2019_12
>> >>> >>> >>> _22.pdf
>> >>> >>> >>>
>> >>> >>> >>> 1. Distributions of kinematics (MMSQ, dt, d\beta) for
>> particles
>> >>> in
>> >>> >>> >>> lower momentum ranges are plotted to see whether lower
>> momentum
>> >>> >>> >>> particles are of any use for my asymmetry calculation.
>> >>> >>> >>>
>> >>> >>> >>> 2. Proton selection, using beta difference, was revised to a
>> >>> >>> simpler
>> >>> >>> >>> version where static cuts on beta diff are applied at +/-
>> 0.06
>> >>> >>> >>>
>> >>> >>> >>>
>> >>> >>> >>> Thank you,
>> >>> >>> >>> Chan
>> >>> >>> >>>
>> >>> >>> >>> _______________________________________________
>> >>> >>> >>> Frost mailing list
>> >>> >>> >>> Frost at jlab.org
>> >>> >>> >>> https://mailman.jlab.org/mailman/listinfo/frost
>> >>> >>> >>>
>> >>> >>> >>
>> >>> >>> >> _______________________________________________
>> >>> >>> >> Frost mailing list
>> >>> >>> >> Frost at jlab.org
>> >>> >>> >> https://mailman.jlab.org/mailman/listinfo/frost
>> >>> >>> >
>> >>> >>> > --
>> >>> >>> > Dr Stuart Fegan
>> >>> >>> > Honorary Research Associate
>> >>> >>> > Nuclear Physics Group
>> >>> >>> > University of Glasgow
>> >>> >>> > (Currently at the University of York)
>> >>> >>> >
>> >>> >>> > E-mail: s.fegan.glasgow at gmail.com
>> >>> >>> >
>> >>> >>> > _______________________________________________
>> >>> >>> > Frost mailing list
>> >>> >>> > Frost at jlab.org
>> >>> >>> > https://mailman.jlab.org/mailman/listinfo/frost
>> >>> >>> >
>> >>> >>>
>> >>> >>>
>> >>> >>> _______________________________________________
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>> >>> >>
>> >>> >
>> >>> >
>> >>> >
>> >>>
>> >>>
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>> >>>
>> >>
>> >
>>
>>
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