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

Chan Kim kimchanwook at gwmail.gwu.edu
Mon Dec 23 15:47:57 EST 2019 

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