> Ideally, one would wish to express the corrections of
> reconstructed variables as a function of a
> detector-specific coordinate (such as position along
> the wire chamber plane).
I think this is an oversimplification for no other reason
than the extended target.
> I assume in P.ps the electron offsets are plotted vs.
> p_e (not p_p) and in TH.ps the electron offsets are
> plotted vs. th_e (not th_p)?
Correct assumptions.
> For the "residual" kinematic offsets, they may depend
> both on angle and momentum, however elastic scattering
> can determine these offsets only as a function of one
> coordinate (e.g. momentum) because the other coordinate
> (angle) is again correlated with the first one.
My offsets are actually a function of TOF and thus don't
necessarily fit into this description.
Not positive I completely understand this, but if I do,
I think that a wire chamber polar angle rotation would
result in a wrong theta but not a momentum shift. I'm
not sure how this would fit into your argument.
> If we believe that the origin of the residual offsets
> is a property of the detector, then my feeling says it
> may be better to express them as a function of the
> angle rather than the momentum. Reason is that the
> corrections expressed as function of angle may be
> applicable to other channels as well (such as pion
> production) which cover significantly different
> momentum regions for the same angle.
This would probably require a completely different
benchmark for categorization. Small polar angle
electrons from pion production will probably show bad
momentum resolution due to the angle at which they
cross the plane of wires in the chambers. This would
happen at a higher polar angle than ep-elastic (i.e.
30 degrees instead of 25). This would already imply
a poor residual offset at 30 degrees.
Let's just pray for Wire chamber geometry. I'm starting
to brainstorm my own method for nailing down the
geometry. I doubt it will work since I can't even get
a kine.init link to run properly, but we'll see.
-eugene
Quoting Michael Kohl <kohlm@mit.edu>:
> A have a few remarks:
> Since here we talk about Eloss, the corrections are really only
> functions
> of the momentum, and the angle dependence only comes through the
> momentum-angle correlation for elastic scattering.
>
>
>
>
> Regards,
>
> Michael
>
>
>
>
> On Fri, 10 Mar 2006, Eugene J. Geis wrote:
>
> > Proton's momentum loss can be parameterized over
> > momentum or over theta. The high polar angle and
> > low momentum occupy the same phase space so use only
> > one. The parameterizations were done by comparing
> > reconstructed MonteCarlo with Eloss on and Eloss off,
> > MASCARAD was off for both MonteCarlo runs and thus
> > plays no part in this parameterization. Electrons
> > proved to not need any parameterization as should
> > be expected.
> >
> > The following polynomials should be added to the
> > reconstructed momentum in order to "bump up" the
> > proton's momentum to the proper momentum.
> >
> > Root's 4th degree polynomial fit over
> > energy lost vs. momentum gives the following:
> >
> >
> > p0 3.05683e-02
> > p1 -1.64857e-01
> > p2 3.34062e-01
> > p3 -2.99825e-01
> > p4 1.00794e-01
> >
> >
> > Root's 4th degree polynomial fit over
> > energy lost vs. theta gives the following:
> >
> >
> > p0 5.97905e-02
> > p1 -5.29057e-03
> > p2 1.73551e-04
> > p3 -2.49832e-06
> > p4 1.33493e-08
> >
> >
> > Attached graphs can be interpreted as the titles
> > given for each plot.
> >
> > Note: For P.ps and TH.ps, the two plots on the left
> > side are for ELOSS ON, and the two plots on the
> > right side are for ELOSS OFF!
> >
> > PARAM.ps is a plot of the profiles subtracted from
> > each other. Cuts for good ep-elastic data are
> >
> > TCut Cutst_L("(qwl==-1&&qwr==1&&
> > abs(sqrt((0.85-pwl+0.938272)**2 -
> > 0.85*(0.85-2.*pwl*cos(twl*0.01745))-pwl**2)-0.938)<0.04 &&
> abs(fwl-fwr+180.)<3.0)");
> >
> > TCut Cutst_R("(qwl==1&&qwr==-1&&
> > abs(sqrt((0.85-pwr+0.938272)**2 -
> > 0.85*(0.85-2.*pwr*cos(twr*0.01745))-pwr**2)-0.938)<0.04 &&
> abs(fwl-fwr+180.)<3.0)");
> >
>
>
> +-------------------------------------+--------------------------+
> | Office: | Home: |
> |-------------------------------------|--------------------------|
> | Dr. Michael Kohl | Michael Kohl |
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> | Middleton, MA 01949 | U.S.A. |
> | U.S.A. | |
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> | http://blast.lns.mit.edu | |
> +-------------------------------------+--------------------------+
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
--------------------------------------------------------------------------
Eugene Geis
PhD Student, Physics Department, ASU
Research Affiliate, MIT-Bates Laboratory of Nuclear Science
eugene.geis@asu.edu
--------------------------------------------------------------------------
http://quickreaction.blogspot.com
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