[Clas_lmd] lepton pion PID

Michael C. Kunkel mkunkel at jlab.org
Fri Jul 10 17:22:21 EDT 2015 

Greetings,

"
and plot missing mass of proton Mx(p)^2 under the same cuts as above 
with e+e- replaced by pi+pi-
and see a peak of eta then this would have been an ambiguity
and would have prevented to identify Dalitz decay.

"

This is exactly what you show in
http://www.lions.odu.edu/~mamaryan/all_mxp.pdf
You see an eta peak in both, meaning there is ambiguity.

BR
MK
----------------------------------------
Michael C. Kunkel, PhD
Forschungszentrum Jülich
Nuclear Physics Institute and Juelich Center for Hadron Physics
Experimental Hadron Structure (IKP-1)
www.fz-juelich.de/ikp

On 7/10/15 2:55 PM, Amaryan, Moskov wrote:
> Hi Michael,
>
> From the same experiment two decay modes have perfect right to exist, 
> namely eta->pi+pi-\gamma and eta->e+e-\gamma.
>
> However if we select events which pass the following cuts:
>
> 1. missing mass squared abs(Mx(e+e-\gamma))^2 <0.01
> 2. missing energy squared Ex = E_beam + Mp - E(e+) -E(e-) >0.2
>
> and plot missing mass of proton Mx(p)^2 under the same cuts as above 
> with e+e- replaced by pi+pi-
> and see a peak of eta then this would have been an ambiguity
> and would have prevented to identify Dalitz decay.
>
> But,  this was not the case, as I showed in LMD meeting.
>
> Best regards,
> Moskov.
>
>
> On Jul 10, 2015, at 9:56 PM, Michael C. Kunkel <mkunkel at jlab.org 
> <mailto:mkunkel at jlab.org>> wrote:
>
>> Greetings,
>>
>>
>> "
>> Although it is not clear to me what are we going to learn from the 
>> requested plot I created it from g11 data.
>> See it here:
>> "
>> As you can see from your plots, middle and bottom, that there exists 
>> eta regardless of mass assignment. This means just assigning lepton 
>> mass does not necessarily mean they are leptons.
>>
>
>
>
>> "
>> It would have been more interesting to compare the same plots from 
>> g12 to understand which dataset is
>> more powerful statistically in particular channels.
>> "
>>
>> See my last email.
>> BR
>> MK
>> ----------------------------------------
>> Michael C. Kunkel, PhD
>> Forschungszentrum Jülich
>> Nuclear Physics Institute and Juelich Center for Hadron Physics
>> Experimental Hadron Structure (IKP-1)
>> www.fz-juelich.de/ikp
>> On 7/10/15 1:51 PM, Amaryan, Moskov wrote:
>>> Dear all,
>>>
>>> Although it is not clear to me what are we going to learn from the 
>>> requested plot I created it from g11 data.
>>> See it here:
>>>
>>> http://www.lions.odu.edu/~mamaryan/all_mxp.pdf 
>>> <http://www.lions.odu.edu/%7Emamaryan/all_mxp.pdf>
>>> The upper panel is invariant mass of e+e-\gamma squared, the middle 
>>> one is for M_{x}(p)^2 with electron assignment,
>>> the lower one is the same with pion mass assignment.
>>>
>>> It would have been more interesting to compare the same plots from 
>>> g12 to understand which dataset is
>>> more powerful statistically in particular channels.
>>>
>>> Best regards,
>>> Moskov.
>>>
>>>> ________________________________________
>>>> From: Clas_lmd [clas_lmd-bounces at jlab.org 
>>>> <mailto:clas_lmd-bounces at jlab.org>] on behalf of Michael C. Kunkel 
>>>> [mkunkel at jlab.org <mailto:mkunkel at jlab.org>]
>>>> Sent: Thursday, July 09, 2015 7:02 AM
>>>> To: clas_lmd at jlab.org <mailto:clas_lmd at jlab.org>
>>>> Subject: Re: [Clas_lmd] lepton pion PID
>>>>
>>>> Greetings,
>>>>
>>>> Can you overlay the MxP^2 with pion mass setting on this plot? 
>>>> Using the same kinematic cuts except with pion pid?
>>>>
>>>>
>>>>
>>>> BR
>>>> MK
>>>> ----------------------------------------
>>>> Michael C. Kunkel, PhD
>>>> Forschungszentrum Jülich
>>>> Nuclear Physics Institute and Juelich Center for Hadron Physics
>>>> Experimental Hadron Structure (IKP-1)
>>>> www.fz-juelich.de/ikp 
>>>> <http://www.fz-juelich.de/ikp><http://www.fz-juelich.de/ikp>
>>>>
>>>> On 7/9/15 1:11 AM, Amaryan, Moskov wrote:
>>>> Dear all,
>>>>
>>>> I attach a plot with Mx(p)^2 and M(e+e-\gamma)^2 distributions 
>>>> overlaid. Statistics of both histograms are the same,
>>>> however, as one can see there is no peak of eta in the invariant 
>>>> mass squared, data are from g11.
>>>> Invariant mass has no eta in it similar  to what Michael showed for 
>>>> g12.
>>>> One can think of two possibilities, either these are true eta’s 
>>>> decaying to e+e-\gamma, or these are  remnants of eta->pi+pi-gamma 
>>>> events.
>>>> The latter hypothesis was ruled out by plotting invariant mass of 
>>>> pi+pi-\gamma or missing mass of proton for pion mass assignment
>>>> for the same events that make Mx(p)^2 under lepton assignment.
>>>>
>>>> Best regards,
>>>> Moskov.
>>>>
>>>> On Jul 8, 2015, at 11:02 PM, Amaryan, Moskov <MAmaryan at odu.edu 
>>>> <mailto:MAmaryan at odu.edu><mailto:MAmaryan at odu.edu>> wrote:
>>>>
>>>> Hi Michael,
>>>>
>>>> Thanks for your message, looks interesting.
>>>>
>>>> However we have shown in the CAA and also Georgie has shown it in 
>>>> our meetings that invariant mass of pi+pi-\gamma
>>>> resolution is much worse than missing mass of  proton.  The reason 
>>>> is energy resolution of the final state photon and
>>>> vertex resolution as momentum of the photon is defined through both 
>>>> of these, energy and vertex.
>>>> Therefore we use missing mass of  proton with other cuts, which use 
>>>> pion mass assignment to \pi^+ and \pi^-.
>>>>
>>>> Now what I have shown on Tuesday, was missing mass of proton with 
>>>> electron (positron) mass assignments.
>>>> There we clearly see a peak of eta. The mass assignment is 
>>>> arbitrary, of course, but requirement of missing mass squared
>>>> of pe+e- to be around zero (<0.01 GeV) and missing energy of pe+e- 
>>>> to be E_x>0.2 GeV makes this selection definite, not arbitrary.
>>>> And the fact that we see peak of eta is a proof that some of pi+pi- 
>>>> tracks are actually e+e- pairs
>>>>
>>>> The plot you sent around doesn’t show a peak of eta very clearly in 
>>>> the best topology with EC/CC, but one can imagine that with more 
>>>> statistics
>>>> the  eta peak will be visible. However without EC/CC there is no 
>>>> signature of eta whatsoever. Would it be visible in the missing 
>>>> mass of proton in g12?
>>>>
>>>> It wouldn’t make sense for me to argue that PID on leptons improves 
>>>> invariant mass e+e-\gamma, of course it does.
>>>>
>>>> The question was which fraction of events that make eta in the 
>>>> missing mass of proton with e+e-\gamma assignment is due to events 
>>>> that were
>>>> from pi+pi-\gamma final state.
>>>> I think we have shown that this fraction is negligible.
>>>>
>>>> It will be interesting to compare missing mass of the proton 
>>>> squared from g11 and g12 (for pe+e-gamma final state)  to see if 
>>>> because of different
>>>> acceptances these two data sets have similar or very different 
>>>> numbers of eta’s.
>>>>
>>>> It appeared that ntuples we are using from g11 have been eloss 
>>>> applied. In this case eloss for pions and leptons will be the same, 
>>>> I am not sure how different they should be, but the fact that we 
>>>> see peaks of pi0 and eta in the missing mass of proton is 
>>>> indicative that in the first approximation we can neglect eloss 
>>>> uncertainties.
>>>>
>>>> Best regards,
>>>> Moskov.
>>>>
>>>> On Jul 8, 2015, at 1:33 PM, Michael C. Kunkel <mkunkel at jlab.org 
>>>> <mailto:mkunkel at jlab.org><mailto:mkunkel at jlab.org>> wrote:
>>>>
>>>> Greetings,
>>>>
>>>> So I was curious to reproduce my study on pion contamination 
>>>> without the use of CC or EC quantities.
>>>> I am attaching a plot that shows G12 data that shows 3 lines.
>>>> Red: G12 data with eloss on pions, pion mass setting, invariant 
>>>> mass PipPimGam; conditions Ngamma > 0 && abs(mm2_PPipPimGam)<0.01 
>>>> && mE_PPipPim > 0.2
>>>>
>>>> Blue: G12 data with eloss on leptons,lepton mass setting , 
>>>> invariant mass EpEmGam; conditions Ngamma > 0 && 
>>>> abs(mm2_PEpEmGam)<0.01 && mE_PEpEm > 0.2
>>>>
>>>> Cyan: G12 data with eloss on leptons,lepton mass setting , 
>>>> invariant mass EpEmGam; conditions Ngamma > 0 && 
>>>> abs(mm2_PEpEmGam)<0.01 && mE_PEpEm > 0.2 && lepton PID through CC 
>>>> and EC. Histogram is scale by x10
>>>>
>>>>
>>>> As I concluded years ago, and is seen in the histogram, without CC 
>>>> or EC, the eta peak cannot be reproduced in the proper place.
>>>>
>>>> Total data used:1/463 of g12 data set.
>>>>
>>>> Hope this helps.
>>>>
>>>>
>>>> BR
>>>> MK
>>>> ----------------------------------------
>>>> Michael C. Kunkel, PhD
>>>> Forschungszentrum Jülich
>>>> Nuclear Physics Institute and Juelich Center for Hadron Physics
>>>> Experimental Hadron Structure (IKP-1)
>>>> www.fz-juelich.de/ikp 
>>>> <http://www.fz-juelich.de/ikp><http://www.fz-juelich.de/ikp>
>>>>
>>>>
>>>>
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>>>> <Lepton_Pion_mass_comparision.pdf>_______________________________________________
>>>> Clas_lmd mailing list
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>>>>
>>>> Prof. Moskov Amaryan
>>>> Department of Physics
>>>> Old Dominion University
>>>> 4600 Elkhorn Avenue
>>>> Norfolk, VA 23529
>>>>
>>>> phone:757-683-4614
>>>>
>>>>
>>>>
>>>> ________________________________
>>>>
>>>> Spam<about:blank>
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>>>> Forget previous vote<about:blank>
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>>>> Clas_lmd mailing list
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>>>>
>>>> Prof. Moskov Amaryan
>>>> Department of Physics
>>>> Old Dominion University
>>>> 4600 Elkhorn Avenue
>>>> Norfolk, VA 23529
>>>>
>>>> phone:757-683-4614
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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>>>>
>>>> ________________________________
>>>>
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>>>
>>> Prof. Moskov Amaryan
>>> Department of Physics
>>> Old Dominion University
>>> 4600 Elkhorn Avenue
>>> Norfolk, VA 23529
>>>
>>> phone:757-683-4614
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Clas_lmd mailing list
>>> Clas_lmd at jlab.org
>>> https://mailman.jlab.org/mailman/listinfo/clas_lmd
>>
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>
> Prof. Moskov Amaryan
> Department of Physics
> Old Dominion University
> 4600 Elkhorn Avenue
> Norfolk, VA 23529
>
> phone:757-683-4614
>
>
>

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