[Clas_lmd] lepton pion PID

Thu Jul 9 08:09:44 EDT 2015

Dear Michael,

I am afraid but I do not understand - you are asking everybody or somebody
in particular?  I, for instance, cannot provide you a distribution which
your ordering. Sure, I can but it will take a time

Cheers, Igor

On Thu, 09 Jul 2015 07:02:21 -0400, "Michael C. Kunkel" <mkunkel at jlab.org> 
wrote:

> 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
> 
> 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>> 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>> 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>
>>>>
>>>>
>>>>
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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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>>
>> Prof. Moskov Amaryan
>> Department of Physics
>> Old Dominion University
>> 4600 Elkhorn Avenue
>> Norfolk, VA 23529
>>
>> phone:757-683-4614
>>
>>
>>
>>
>>
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> 

Igor Strakovsky, SAID CNS The George Washington University
Tel: 703-726-8344(NV),202-994-4742(FB),Skype: igors1945_2
Fax: 202-994-3001(FB),Emails: igor at va.gwu.edu, igor at jlab.org