[G12] similar study of eloss in g11
Eugene Pasyuk
pasyuk at jlab.org
Wed Sep 14 16:35:05 EDT 2011
A few comments.
1. GSIM by default does energy losses. Therefore, when you analyze gsim
data you should apply eloss corrections the same way you do with real data.
2. in addition to eloss there are always run period dependent momentum
corrections.
3. often we also need to apply photon energy corrections. They may be
caused by the incorrect electron beam energy and/or some other reasons
like focal plane sag etc.
You have to check this. For this we usually use overdetermined
kinematics when you can extract photon energy from measured momenta of
exclusive final state particles. Usually we us gp->pi+pi-p when all
three particles detected. Then you can compare measured vs. predicted
photon energy. Look at this difference (or ratio) vs. Eid.
You can use kinematic fit to get corrections 2 and 3.
-Eugene
On 9/14/11 13:22 , John Price wrote:
> John Goetz and I looked into this some time back. My recollection is
> that we determined that the energy loss card in GSIM has no effect
> whatsoever. Energy loss is *always* applied, regardless of the setting
> of the FFREAD card.
>
> John
>
> On Wed, 2011-09-14 at 09:19 -0700, Lei Guo wrote:
>> I agree with you. MC data should also be able to tell us how much the
>> neutron peak will be moved due to eloss. It seems to me that the shift
>> in the data -- excluding the effect of the electron beam energy --- IS
>> too big.
>>
>> Lei
>> On Sep 15, 2011, at 3:03 AM, mpaolone at jlab.org wrote:
>>
>>> I thought that gsim removes energy from the tracks depending on what
>>> materials they pass through, then you must run eloss in your
>>> analysis to
>>> recover what gsim removed. I also think that gsim removes energy
>>> from the
>>> tracks by default, and you have to turn off a switch somewhere to
>>> get rid
>>> of that functionality if you want to. I am not a gsim expert, and if
>>> anyone else has a different understanding, please correct me.
>>>
>>> -Michael
>>>
>>>
>>>> I don't recall a conclusive answer as to whether or not GSIM data
>>>> requires eloss to be applied (see attached).
>>>>
>>>>
>>>> On 09/13/2011 02:41 PM, Lei Guo wrote:
>>>>> HI, Craig,
>>>>>
>>>>> Nathan Baltzell did a very comprehensive study of eloss for g11.
>>>>> What
>>>>> I recall is that he uncovered quite a few mistakes here and there,
>>>>> mostly on the gsim side, by comparing the delta_P (momentum change)
>>>>> as a function of various variables (vertex positions, theta,
>>>>> momentum,
>>>>> etc) using both real data and simulation. I think you already have
>>>>> the
>>>>> all the info now. It might be worthwhile now to make sure that we
>>>>> did
>>>>> eloss correctly, by checking the delta_p's as a function of z,
>>>>> theta,
>>>>> p, and it should be similar to what gsim has, if we are doing eloss
>>>>> correctly.
>>>>>
>>>>> Personally, I still think the low mass might come from the shifted
>>>>> electron beam energy.
>>>>>
>>>>> Lei
>>>>>
>>>>>
>>>>>
>>>>> On Sep 14, 2011, at 6:45 AM, Craig Bookwalter wrote:
>>>>>
>>>>>> Hi folks,
>>>>>> I've posted a few more things to the wiki in relation to our
>>>>>> discussion Friday about the issues I'm having with energy loss
>>>>>> and the
>>>>>> mass of the neutron being too low:
>>>>>>
>>>>>> http://clasweb.jlab.org/rungroups/g12/wiki/index.php/Charged_3pi_event_selection#Neutron_Mass
>>>>>>
>>>>>>
>>>>>> Specifically, Mike Paolone and I each did our own eloss
>>>>>> corrections to
>>>>>> a
>>>>>> common set of events and I find our corrections to be identical. In
>>>>>> addition, I've examined a sample of p pi+ pi- events and when I
>>>>>> reconstruct the proton via missing mass off the pi+pi-, I see a
>>>>>> similar
>>>>>> underestimation of the mass of the proton.
>>>>>>
>>>>>> Feel free to ponder this til Friday, or respond now via the list
>>>>>> if you
>>>>>> so desire. Any ideas are welcome.
>>>>>>
>>>>>> --cb
>>>>>>
>>>>>>
>>>>>> --
>>>>>> -------------------------------------------------------------------------
>>>>>>
>>>>>> Craig Bookwalter FSU Office: (850) 644 3808
>>>>>> Department of Physics JLab Office: (757) 269 5465
>>>>>> Florida State University craigb at hadron.physics.fsu.edu
>>>>>> Tallahasse, FL 32306 craigb at jlab.org
>>>>>>
>>>>>> "Tower, this is Ghostrider requesting a flyby."
>>>>>> -------------------------------------------------------------------------
>>>>>>
>>>>>>
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>>>>> **************************************
>>>>> @
>>>>> / *
>>>>> / ___ ___ Lei Guo _______________________
>>>>> L_O_/ ____ Florida International University____/_/
>>>>> \ | Physics Dept., CP 212
>>>>> / /
>>>>> / \ | Miami, FL 33199
>>>>> / / /
>>>>> / I_/ \ ____ USA _____ /______/__________/ /
>>>>> / / L / /
>>>>> / / /
>>>>> / / / /
>>>>> / / /
>>>>> /_/__________/______/______/__________/_/
>>>>> /_/__________/______/______/__________/_/
>>>>> 305-348-0234(o)
>>>>>
>>>>> **************************************
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> --
>>>> -------------------------------------------------------------------------
>>>> Craig Bookwalter FSU Office: (850) 644 3808
>>>> Department of Physics JLab Office: (757) 269 5465
>>>> Florida State University craigb at hadron.physics.fsu.edu
>>>> Tallahasse, FL 32306 craigb at jlab.org
>>>>
>>>> "Tower, this is Ghostrider requesting a flyby."
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>>>>
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>> **************************************
>> @
>> / *
>> / ___ ___ Lei Guo _______________________
>> L_O_/ ____ Florida International University____/_/
>> \ | Physics Dept., CP
>> 212 / /
>> / \ | Miami, FL
>> 33199 / / /
>> / I_/ \ ____ USA _____ /______/__________/ /
>> / /
>> L
>> / / / / /
>> / / / / / / /
>> /_/__________/______/______/__________/_/
>> /_/__________/______/______/__________/_/
>> 305-348-0234(o)
>>
>> **************************************
>>
>>
>>
>>
>>
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