Re: A note on mass resolutions in GlueX/HallD

[Elke-Caroline Aschenauer <elke@jlab.org>]

On Sat, 15 Mar 2008, Prof Paul Eugenio wrote:

Dear Paul,

thanks for the plots very nice. espcially that the resilts from Alex and
you are so close. I have a small question would it not better to fit
the distributions with a breit wigner instead of a gaussian.
I think it would be also good to use some background function below the
fit should improve a lot and the width I guess will become smaller.

cheers elke


> Date: Sat, 15 Mar 2008 13:02:24 -0400
> From: Prof Paul Eugenio <eugenio@fsu.edu>
> To: Alex Dzierba <dzierba@indiana.edu>
> Cc: halld-pid@jlab.org, GlueX Tracking <halld-tracking-hw@jlab.org>,
>      GlueX Software <HallD-Offline@jlab.org>
> Subject: Re: A note on mass resolutions in GlueX/HallD
>
> Hi Alex,
>
> Last night I ran some 3pi generated event through the new smearing
> functions.  The events were generated with e^-5t distribution, and
> weighted with Adam's 3pi cross section what we used in the blind PWA
> studies.  I subjected these events to fiducial cuts where events were
> accepted if  0.150 GeV < p_pion < 7 GeV and  1 deg < theta_pion < 140
> deg.   These events were then smeared using the new functions.  I found
> that the new routine return unsmeared momenta above 7GeV so I cut these
> out.  I also smeared the beam by an expected(RTJ) 0.06% (0.02%
> accelerator + 0.04% tagger).
>
> I have attached 3 figures.  The file 3pi_newSmear.pdf shows the t, 3pi,
> 2 PiPlus, 2pi, mmsq, and cos_GJ.   A fit to the mmsq over the same range
> as in your report results in a sigma of 0.27 GeV^2 (chisq/dof = 3.7).
> This is in good agreement with your result (0.33 GeV^2) and shows a
> slight improvement as expected.
>
> In your report you compared to an e852 sigma of 0.31 GeV^2. I came
> across a different published E852 mmsq sigma result.  In Phys. Rev. D65
> 072001, the mmsq has a sigma of 0.26 GeV^2(I have attached a clip from
> the paper in the file e852-3pi-mmsq.jpg).  Note that E852 fit was over a
> wider range. I tried a fit over this same mmsq range.   The result was a
> sigma of 0.30 GeV^2 but much poorer fit ( chisq/dof = 7.6 ).   See plot
> in 3pi_new-mmsq-compare2E852.pdf.
>
> Paul
>
>
> --
> --
> Prof. Paul Eugenio
> Department of Physics
> Florida State University
> Tallahassee, FL  USA
>
> 850-644-2585
> eugenio@fsu.edu
>

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3pi_newSmear.pdf

e852-3pi-mmsq.jpg

3pi_new-mmsq-compare2E852.pdf