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

[Michael Dugger]

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
>>> >>> >>>
>>> >>> >>> _______________________________________________
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>>> >>> >>>
>>> >>> >>
>>> >>> >> _______________________________________________
>>> >>> >> 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
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>>> >>> > https://mailman.jlab.org/mailman/listinfo/frost
>>> >>> >
>>> >>>
>>> >>>
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>>> >>
>>> >
>>> >
>>> >
>>>
>>>
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>>
>