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

Thu Dec 26 16:31:03 EST 2019

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.Ã‚  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?Ã‚  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
> >>> >>> >
> >>> >>>
> >>> >>>
> >>> >>> _______________________________________________
> >>> >>> Frost mailing list
> >>> >>> Frost at jlab.org
> >>> >>> https://mailman.jlab.org/mailman/listinfo/frost
> >>> >>
> >>> >
> >>> >
> >>> >
> >>>
> >>>
> >>> _______________________________________________
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> >>> https://mailman.jlab.org/mailman/listinfo/frost
> >>>
> >>
> >
>
>
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