[G12] similar study of eloss in g11
John Price
jprice at csudh.edu
Wed Sep 14 16:39:48 EDT 2011
Restating my previous:
What we concluded is that not only does GSIM do energy loss by default,
there is *no* way (within GSIM, at least) to shut energy loss off.
Standard GEANT does allow for this possibility, which somehow is
*disabled* within GSIM.
John
On Wed, 2011-09-14 at 13:35 -0700, Eugene Pasyuk wrote:
> 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 _____ /______/__________/ /
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> >>>>> / / / /
> >>>>> / / /
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> >>>>> /_/__________/______/______/__________/_/
> >>>>> 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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> >> **************************************
> >> @
> >> / *
> >> / ___ ___ 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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--
John W. Price
Professor and Chair of Physics
CSU Dominguez Hills
310-243-3403
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