[Hps-analysis] Moller Generator Fixed! (again)

Sat May 14 13:05:51 EDT 2016

Hi Takashi,
Thanks for the prompt reply. So you are saying that the we have no acceptance for Moller electrons at all. 
Your conclusion is in contradiction with Geant MC and our data, I believe.
It will be interesting to understand the reason.
- Did you really apply the geometrical cut or made your conclusion based on your first picture by eye? Picture N2 shows that 1.15 GeV electrons has X=(-10,-15)cm spread.
- The solid line is just the edge of the crystals at the face of the calorimeter, correct?
- What if we will apply the crystal's edge cut at the back of the calorimeter, not at the front face?
- We have 30 mrad angle for beam particles on our target. Do you have it in your fast MC?
- Can you make your plots for the electrons that have hit in the calorimeter?

Thanks again,
Valery


----- Original Message -----
> From: "Takashi Maruyama" <tvm at slac.stanford.edu>
> To: "Valery Kubarovsky" <vpk at jlab.org>
> Cc: "Sho Uemura" <meeg at slac.stanford.edu>, "Bradley T Yale" <btu29 at wildcats.unh.edu>, "Maurik Holtrop"
> <maurik at physics.unh.edu>, hps-analysis at jlab.org, "hps-software" <hps-software at slac.stanford.edu>, "Norman A. Graf"
> <ngraf at slac.stanford.edu>
> Sent: Friday, May 13, 2016 6:13:31 PM
> Subject: RE: [Hps-analysis] Moller Generator Fixed! (again)

> Hi Valery,
> 
> Attached is the distributions you requested. These are Brad's EGS5 generated
> Mollers. If I use the solid lines to represent the crystal edges, one of the
> Moller electrons always falls in this removed crystal area; ie both e-'s cannot
> be detected by ECal.
> 
> Takashi
> 
> -----Original Message-----
> From: Valery Kubarovsky [mailto:vpk at jlab.org]
> Sent: Friday, May 13, 2016 12:08 PM
> To: Maruyama, Takashi
> Cc: Uemura, Sho; Bradley T Yale; Maurik Holtrop; hps-analysis at jlab.org;
> hps-software; Graf, Norman A.
> Subject: Re: [Hps-analysis] Moller Generator Fixed! (again)
> 
> Hi Takashi,
> 
> Can you make a several plots from your fast MC:
> 
> 1. Y vs X of the tracks at the face-off the calorimeter:
> 2. The same plot when both of tracks are detected by Ecal 3. The energy
> distribution of the electrons for the events when both tracks detected by Ecal.
> 
> I think that it is not very difficult for you.
> The main question to resolve will get the dip in the energy distribution or bump
> at the E=Ebeam/2.
> 
> Thanks in advance,
> Valery
> 
> 
> 
> ----- Original Message -----
>> From: "Takashi Maruyama" <tvm at slac.stanford.edu>
>> To: "Sho Uemura" <meeg at slac.stanford.edu>, "Bradley T Yale"
>> <btu29 at wildcats.unh.edu>
>> Cc: "Maurik Holtrop" <maurik at physics.unh.edu>, hps-analysis at jlab.org,
>> "hps-software" <hps-software at slac.stanford.edu>, "Valery Kubarovsky"
>> <vpk at jlab.org>, "Norman A. Graf" <ngraf at slac.stanford.edu>
>> Sent: Friday, May 13, 2016 1:28:29 PM
>> Subject: RE: [Hps-analysis] Moller Generator Fixed! (again)
> 
>> Thanks, Sho. I was going to say exactly the same thing. Attached is
>> Moller distribution at layer 6 in my fast tracking using Brad's Moller
>> events. Moller problem is somewhere else.
>>   Takashi
>> 
>> -----Original Message-----
>> From: hps-software at slac.stanford.edu
>> [mailto:hps-software at slac.stanford.edu] On Behalf Of Sho Uemura
>> Sent: Friday, May 13, 2016 9:00 AM
>> To: Bradley T Yale
>> Cc: Maurik Holtrop; hps-analysis at jlab.org; hps-software; Valeri
>> Koubarovski; Graf, Norman A.
>> Subject: Re: [Hps-analysis] Moller Generator Fixed! (again)
>> 
>> By the usual definition of theta_y (angle of elevation from the xz
>> plane), the direction cosine cos(b) (where b is the angle of
>> inclination from the
>> y-axis) exactly equals sin(theta_y).
>> 
>> What I meant to say is that in small angle, sin(theta_y)~=theta_y. The
>> relation
>> sin(theta)sin(phi)=sin(theta_y) is exact.
>> 
>> On Fri, 13 May 2016, Bradley T Yale wrote:
>> 
>>> Even if theta is a small angle, it is multiplied by sin(phi), where phi is not.
>>> ________________________________________
>>> From: hps-software at SLAC.STANFORD.EDU <hps-software at SLAC.STANFORD.EDU>
>>> on behalf of Sho Uemura <meeg at slac.stanford.edu>
>>> Sent: Friday, May 13, 2016 11:00:46 AM
>>> To: Maurik Holtrop
>>> Cc: Bradley T Yale; hps-analysis at jlab.org; HPS Software; Valeri
>>> Koubarovski; Norman A. Graf
>>> Subject: Re: [Hps-analysis] Moller Generator Fixed! (again)
>>>
>>> I don't understand - I thought this cut was intended as a theta_y cut
>>> (>10 mrad above or below the beam plane,so we only keep particles
>>> that might hit a detector), and does v(np) not correctly describe theta_y?
>>>
>>> So I buy that this explains the difference in the envelope of your MC
>>> truth distribution from theory (the U shape) but not that this has
>>> anything to do with the gap, or any data-MC discrepancy seen after
>>> readout.
>>>
>>> On Fri, 13 May 2016, Maurik Holtrop wrote:
>>>
>>>> Hi Bradley,
>>>>
>>>> That is great investigative work. You should now indeed check the
>>>> other EGS5 generators for similar issues. As we discussed yesterday,
>>>> there may be an issue with the background events for tridents.
>>>>
>>>> Can you please mention (advertise) this new result at the analysis
>>>> meeting today?
>>>>
>>>> Best,
>>>>       Maurik
>>>>
>>>>
>>>>> On May 13, 2016, at 3:25 AM, Bradley T Yale <btu29 at wildcats.unh.edu> wrote:
>>>>>
>>>>> I think I found the real problem with how the Moller generator was
>>>>> initially set up.
>>>>> This one affects the generated distribution a LOT more than the RNG
>>>>> precision probably did, and explains the remaining strangeness in
>>>>> the generated distribution.
>>>>>
>>>>> Looking at the egs5 Moller procedure, the angular cut was defined as:
>>>>>
>>>>> abs(v(np)) > 0.010 radians
>>>>>
>>>>> where v(np) is supposed to be theta.
>>>>> However, the variables u, v, and w in egs are actually directional cosines, p_x
>>>>> = p*u,   p_y = p*v,   and   p_z = p*w.
>>>>>
>>>>> So this means that in reality, the generator was saving Moller
>>>>> events such that abs [ sin(theta)*sin(phi) ] > 0.010
>>>>>
>>>>> which has a periodic nature to it. Plot this equation for some
>>>>> value of phi (or just think about it) and you'll see what was
>>>>> likely making these strange hills and gaps in the energy distribution -
>>>>> full-wave rectified Mollers!
>>>>>
>>>>> The scattered beam simulation does correctly define theta though:
>>>>> sqrt[ u^2 + v^2 ]
>>>>>
>>>>> I made a moller_v3 procedure with this correction (still with a >10
>>>>> mrad cut), and the comparison between before and after is shown.
>>>>> The generated events now agree with the calculated cross section
>>>>> (XS curve is shown on the 'bad' plot), and no apparent missing events.
>>>>>
>>>>> These will be run through recon to see if we can finally get good
>>>>> Moller agreement with data.
>>>>> I'm also going to try changing the scattered beam energy cut shown
>>>>> in the software meeting to see if it fixes Tim's phi vs. energy discrepancy.
>>>>> -Brad
>>>>> <BadMollers.png><2pt3_mol_v3_moller_E.png>_________________________
>>>>> _
>>>>> _____________________
>>>>> Hps-analysis mailing list
>>>>> Hps-analysis at jlab.org <mailto:Hps-analysis at jlab.org>
>>>>> https://mailman.jlab.org/mailman/listinfo/hps-analysis
>>>>> <https://mailman.jlab.org/mailman/listinfo/hps-analysis>
>>>>
>>>
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