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

Michael Dugger dugger at jlab.org
Sun Dec 29 11:00:16 EST 2019 

Chan,

Did you use bayesian weighting on the vertex distribution?

Within the z-vertex overlap region, there is no way to distinguish between
the carbon and butanol. This is a physics statement and trumps all of the
machine learning language. It is simply not possible to faithfully sort
carbon and butanol events within the z-vertex overlap region (four-vectors
of momentum and position overlap).

For the machine learning part of your dissertation, you should concentrate
on problems better suited to machine learning. In particular, you should
choose something that is separable. It makes no sense to try and separate
something that cannot be separated.

The mixing of bayesian and neural net should be much more flexible, but
you have to be careful to show everything as a probability.

Take care,
Michael


> Thank you for your comments!! I will make the mmsq comparison plot of the
> first half and second half of the butanol target.
>
> Yes, there is a lot of ambiguity in ML approach and until I find a way to
> probe into how the training is actually done in neural nets, it is still a
> black box that I should not trust.
> My first aim is to correctly produce the results following the simplest
> approaches without any techniques that has unknown errors. Only reason why
> I used machine learning is because my dissertation proposal includes the
> use of machine learning (or at least try) and my graduate committee
> approved on it.
>
> I think there are many obstacles in regards to ML even before trying to
> determine whether results from ML is usable or not. First I need to be
> able
> to know how the training is done and the reasoning behind the
> classification if I am to use the result.
> To do so, I need to have a visualization of how weights are being changed
> as they are being passed on to each neural layers and how they are being
> optimized. Secondly, I need to find a way to compute the uncertainty in
> training. I was trying to build a kind of neural net, called bayesian
> neural network which passes probability density distribution instead of
> scale weights as shown in below figure. Then use the final uncertainties.
>
> Bottom line is, I will not focus on ML until my standard procedures are
> approved and my results on asymmetry E are reasonable.
>
> [image: BayesianNN.png]
>
>
> Thank you,
> Chan
>
>
>
>
> On Sat, Dec 28, 2019 at 10:43 PM Michael Dugger <dugger at jlab.org> wrote:
>
>>
>> Hi,
>>
>> Sounds like a lot of work for little gain. Arguing that the shapes are
>> correct will require more effort than it will be worth, and comparing
>> front to back is not as straight-forward as it might seem (differing
>> amounts of eloss correction and acceptance at low momentum and low
>> angle).
>>
>> If that is how Chan wants to use his time, I will not stand in his way.
>>
>> Take care,
>> Michael
>>
>> > Then in that case it should show up in different dilution factor for
>> the
>> > first half of the target as compared to the second half. This should
>> be
>> > rather straightforward to show.
>> >
>> > If one can argue that the shapes are correct (vertex resolution) one
>> can
>> > use these to tailor the z vertex cuts on a bin by bin basis.
>> >
>> > Sent from my iPhone
>> >
>> >> On 29 Dec 2019, at 02:47, Michael Dugger <dugger at jlab.org> wrote:
>> >>
>> >> Hi,
>> >>
>> >> The same problem applies for the separation of carbon from butanol.
>> >> There
>> >> is no way to distinguish the two types of bound content. The neural
>> net
>> >> is
>> >> making some sort of distinction that, on the face of it, looks
>> >> reasonably
>> >> good. It looks like there are two gaussian distributions that
>> overlap.
>> >> The
>> >> problem is that there is no reason to believe that the separation is
>> in
>> >> any way faithful. Part of the carbon tail in the overlap region is
>> >> actually some combination of carbon and butanol and part of the
>> butanol
>> >> tail in the overlap region is actually some combination of carbon and
>> >> butanol. We just do not know the relative amounts. Perhaps the shapes
>> >> are
>> >> somewhat correct and we could make a good guess as to the proportion
>> of
>> >> each type of events in the overlap?
>> >>
>> >> In short, the separation looks nice but can not be used as
>> representing
>> >> pure samples of carbon (or butanol) in the overlap region.
>> >>
>> >> Take care,
>> >> Michael
>> >>
>> >>> I agree that the classification of free vs bound protons is not
>> >>> possible.
>> >>> What the plot he sent shows (maybe thats just me misreading it) is
>> the
>> >>> classification of events based on target: i.e. butanol vs carbon. If
>> >>> the
>> >>> ML can correctly classify butanol vs carbon events then a vertex cut
>> is
>> >>> not really essential. If he can show that the dilution (ratio of
>> bound
>> >>> to
>> >>> total) is the same between events classified as butanol and events
>> with
>> >>> tight z vertex cuts, that is a first indication that the
>> classification
>> >>> is
>> >>> adequate.
>> >>>
>> >>> I might not be following the discussion or have miss-interpreted
>> >>> things:
>> >>> its 2am here afterall :)
>> >>>
>> >>> Sent from my iPhone
>> >>>
>> >>>>> On 29 Dec 2019, at 00:55, Michael Dugger <dugger at jlab.org> wrote:
>> >>>>
>> >>>> Hi,
>> >>>>
>> >>>> My impression of the machine learning implemented by Chan was that
>> it
>> >>>> was
>> >>>> not able to separate the ice from the carbon.
>> >>>>
>> >>>> The problem is that there is no way to take an event originating
>> from
>> >>>> a
>> >>>> free proton (like that in ice) and distinguish that event from one
>> >>>> that
>> >>>> originates from a bound proton (like that in carbon). Because of
>> this,
>> >>>> the
>> >>>> two types of events are NOT linearly separable.
>> >>>>
>> >>>> Look at it this way: If Chan could remove the signal coming from
>> ice
>> >>>> from
>> >>>> that of carbon, why not just classify the free proton directly from
>> >>>> the
>> >>>> bound content within butanol?
>> >>>>
>> >>>> If machine learning could distinguish free proton from bound, there
>> >>>> would
>> >>>> be no need for a carbon subtraction we would just use machine
>> learning
>> >>>> to
>> >>>> do the separation.
>> >>>>
>> >>>> In the MM-Sq region that is physical, the protons from bound and
>> >>>> unbound
>> >>>> have angles and momentum that overlap and can not be distinguished
>> >>>> from
>> >>>> one another.
>> >>>>
>> >>>> Take care,
>> >>>> Michael
>> >>>>
>> >>>>> Hi Chan,
>> >>>>>
>> >>>>> I dont know the details of your classification, but my first
>> >>>>> impression
>> >>>>> is
>> >>>>> yes. If you have a reliable classification then you can (in
>> >>>>> principle)
>> >>>>> not
>> >>>>> apply z vertex cuts. You can just use your butanol events as
>> chosen
>> >>>>> by
>> >>>>> the
>> >>>>> classification And your carbon events for establishing the bound
>> >>>>> nucleon
>> >>>>> contributions. This would of course need to be studied in a
>> >>>>> systematic
>> >>>>> way
>> >>>>> and a classification uncertainty needs to be established. It looks
>> >>>>> like
>> >>>>> you were also able to remove the ice build up downstream the
>> carbon
>> >>>>> target. Might be good to see the missing masses originating from
>> the
>> >>>>> two
>> >>>>> targets. A quick check for your classification would be to plot
>> the
>> >>>>> missing mass of events coming with z vertex that selects the first
>> >>>>> half
>> >>>>> of
>> >>>>> your target (any events away from the carbon target ). Then scale
>> >>>>> this
>> >>>>> and
>> >>>>> see if you can get the missing mass distribution to match the one
>> >>>>> from
>> >>>>> your classified butanol events. If it does, it means you are
>> >>>>> correctly
>> >>>>> removing any contributions from the carbon target which would only
>> >>>>> contribute to background. If you fail to match the free proton
>> peak
>> >>>>> and
>> >>>>> the bound nucleon contributions it means that the classification
>> >>>>> might
>> >>>>> need some work.
>> >>>>>
>> >>>>> Sent from my iPhone
>> >>>>>
>> >>>>>>> On 28 Dec 2019, at 21:26, Chan Kim <kimchanwook at gwmail.gwu.edu>
>> >>>>>>> wrote:
>> >>>>>>
>> >>>>>> 
>> >>>>>> Thank you for your replies.
>> >>>>>>
>> >>>>>> @Michael,
>> >>>>>> For the z-vertex plot, only p<300MeV particles are removed. I
>> will
>> >>>>>> change the momentum selection region and see how z-vertex
>> resolution
>> >>>>>> changes as soon as I have other steps finished. I kept them for
>> now,
>> >>>>>> so
>> >>>>>> I can compare my asymmetry with and without particles with
>> p=[300,
>> >>>>>> 400]
>> >>>>>> MeV.
>> >>>>>>
>> >>>>>> @Nick,
>> >>>>>> In regards to free polarized proton contributions in carbon
>> vertex
>> >>>>>> (left
>> >>>>>> tail of the carbon distribution), would it be ok to use
>> >>>>>> classification
>> >>>>>> results from machine learning? Below is a plot of separation of
>> >>>>>> butanol
>> >>>>>> and carbon in small angles.
>> >>>>>>
>> https://clasweb.jlab.org/rungroups/g9/wiki/images/0/06/Zvrt_1bin_angle.png
>> >>>>>>
>> >>>>>> Thank you,
>> >>>>>> Chan
>> >>>>>>
>> >>>>>>
>> >>>>>>> On Sat, Dec 28, 2019 at 12:42 PM Nicholas Zachariou
>> >>>>>>> <nickzachariou at gmail.com> wrote:
>> >>>>>>> Dear Chan,
>> >>>>>>>
>> >>>>>>> I have done several studies on this that should be documented in
>> my
>> >>>>>>> analysis note. As Michael said, the difficulty lies in the
>> >>>>>>> determination of the dilution factor. If you are using carbon
>> data
>> >>>>>>> to
>> >>>>>>> determine this, then you need to make sure you account correctly
>> >>>>>>> for
>> >>>>>>> free polarised proton contributions within your carbon vertex
>> cut
>> >>>>>>> that
>> >>>>>>> actually comes from butanol events (this is different than the
>> ice
>> >>>>>>> built up). If you are using parametrization of the bound nucleon
>> >>>>>>> contributions then the dilution is more straightforward, but you
>> >>>>>>> would
>> >>>>>>> need to think/study free unpolarised proton contributions to
>> >>>>>>> butanol
>> >>>>>>> events from the ice built up downstream your carbon target. This
>> >>>>>>> can
>> >>>>>>> been done by varying the butanol z vertex cut andcomparing your
>> >>>>>>> determined observable. There are several ways you can do this
>> and
>> >>>>>>> we
>> >>>>>>> can chat more if needed.
>> >>>>>>>
>> >>>>>>> Best regard,
>> >>>>>>> Nick
>> >>>>>>>
>> >>>>>>> Sent from my iPhone
>> >>>>>>>
>> >>>>>>>> On 28 Dec 2019, at 16:23, Michael Dugger <dugger at jlab.org>
>> wrote:
>> >>>>>>>>
>> >>>>>>>> Chan,
>> >>>>>>>>
>> >>>>>>>> The variables that are important are polar angle and momentum
>> of
>> >>>>>>>> the
>> >>>>>>>> identified particle. Did you keep the low momentum protons?
>> >>>>>>>>
>> >>>>>>>> When it comes to choosing the range of vertex selection for
>> each
>> >>>>>>> target,
>> >>>>>>>> the method you use for removing the bound nucleon content might
>> be
>> >>>>>>>> a
>> >>>>>>>> factor. From the plots you created, you can see the difficulty
>> >>>>>>>> that
>> >>>>>>> you
>> >>>>>>>> face at low angle.
>> >>>>>>>>
>> >>>>>>>> At low polar angle you have the case that there very well could
>> be
>> >>>>>>> some
>> >>>>>>>> leakage of carbon vertices in your butanol definition. This
>> could
>> >>>>>>> cause
>> >>>>>>>> dilution factors to be messed up.
>> >>>>>>>>
>> >>>>>>>> I would cautiously move forward concentrating on the bins that
>> >>>>>>>> look
>> >>>>>>> good.
>> >>>>>>>> Once everything was running well for the "good" stuff, I would
>> >>>>>>>> start
>> >>>>>>>> trying to fix the more difficult bins.
>> >>>>>>>>
>> >>>>>>>> Take care,
>> >>>>>>>> Michael
>> >>>>>>>>
>> >>>>>>>>> Hello Michael,
>> >>>>>>>>>
>> >>>>>>>>> The pi0 mass shifting from 125MeV (slide 2) to 134MeV (slide
>> 6)
>> >>>>>>> happened
>> >>>>>>>>> simply due to a change in number of bins. On slide 6, I tried
>> to
>> >>>>>>> have the
>> >>>>>>>>> same binning for both ELOSS and ELOSS+momentum correction
>> >>>>>>>>> distributions,causing inaccurate peak locations. After
>> momentum
>> >>>>>>>>> correction,
>> >>>>>>>>> the mmsq distribution has much sharper peaks. So, 125MeV is
>> the
>> >>>>>>> correct
>> >>>>>>>>> value of mmsq after ELOSS distribution, but for ELOSS +
>> momentum
>> >>>>>>>>> correction, I will redo the calculation. Sorry for the
>> confusion.
>> >>>>>>>>>
>> >>>>>>>>> I have another question regarding the z-vertex resolution in
>> >>>>>>>>> angles.
>> >>>>>>> Below
>> >>>>>>>>> is a plot that Eugene suggested to make (Z-vertex position in
>> >>>>>>>>> bins
>> >>>>>>> of
>> >>>>>>>>> photon energies and angle bins).
>> >>>>>>>>>
>> https://clasweb.jlab.org/rungroups/g9/wiki/images/a/ac/Zvrt_select_lab.png
>> >>>>>>>>>
>> >>>>>>>>> As you can see, the z-vertex resolution is very poor in small
>> >>>>>>> scattering
>> >>>>>>>>> angles, unable to clearly distinguish the butanol and carbon
>> >>>>>>>>> region.
>> >>>>>>> do
>> >>>>>>>>> you
>> >>>>>>>>> have any suggestions in choosing the selection ranges for
>> small
>> >>>>>>> angles..?
>> >>>>>>>>>
>> >>>>>>>>> Thank you,
>> >>>>>>>>> Chan
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>>> On Thu, Dec 26, 2019 at 4:53 PM Michael Dugger
>> <dugger at jlab.org
>> >
>> >>>>>>> wrote:
>> >>>>>>>>>>
>> >>>>>>>>>> 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
>> >>>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>>>>> _______________________________________________
>> >>>>>>>>>>>>>>>>>> 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
>> >>>>>>>>>>>>>>>
>> >>>>>>>>>>>>>>
>> >>>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>>
>> >>>>>>>>>>>> _______________________________________________
>> >>>>>>>>>>>> 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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