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Re: Fwd: Kfit with timing
Hall D PID Mail List:
Hi Eugene -
thanks for the update on this. Could I also ask you to post your talk
on the GlueX portal. I am trying to make sure that things in the overview
talk are consistent with what is in your talk, so having quick access
to the most up-to-date version would be extremely useful.
On Mon March 24 2008, Eugene Chudakov wrote:
> Hall D PID Mail List:
>
> Hi all,
>
> after messing around a bit with the event fitting I came to an agreement
> with the points made by Matt Belis. Indeed, using the chi2 of the 4C fit,
> (or a reasonably tight Delta(E) separation after the 3C fit) reduces
> the BG dramatically. With a loose cut of CL>1% along with the PID cuts, practically
> no BG from p2pi+2pi- is left.
>
> For the PYTHIA data, the same cuts lead to a signal/all ratio
> of about 90%. After the kin. cut, the proton PID reduces the BG
> by a factor of 3 and the kaon PID - by a factor of 2.
> For twice larger errors on the tracks and beam, the ratio
> becomes 70%, while for 4-times larger errors it becomes 30%.
I am not quite sure that I understand the statement. Is it that you
keep 90% of the signal, or that the accepted signal is 90% of
the accepted background? Or am I really confused here?
>
> If only the 3-mom chi2 is used, the signals/all is about 0.2,
> with the PID suppression factor of about 25.
>
> Thanks to Matt for a nice piece of work and for making his point.
>
> I will change this part of the talk. One may summarize with smth like:
>
> - identification of fully reconstructed events with charged kaons
> should be feasible, providing the expected quality of pattern
> recognition, levels of the background, and understanding of the
> resolutions of the track parameters.
> - Identification of kaon events with a missing particle (a neutron
> recoil, for example), will most likely require an additional PID.
I also suspect that this latter statement is true, however the interesting
test will be to repeat Matt's and your studies treating the nucleon as missing
and performing a 1-C fit.
>
>
> Eugene
>
> ------------------------------------------------------
> Eugene Chudakov
> http://www.jlab.org/~gen
> phone (757) 269 6959 fax (757) 269 5703
>
> On Sat, 22 Mar 2008, Matt wrote:
>
> > Hi Eugene,
> >
> > I've uploaded a summary talk to the portal, GlueX-1009. This talk
> > summarizes what I've done on these PID studies involving pi/K separation.
> > I've also uploaded the source file with all the figures in case you want to
> > include any of them.
> >
> > There's a lot of information there, so I leave it to your discretion what
> > you want to use. But I wanted to make sure there is enough background for
> > you to be able to answer any questions you may or may not get at the review.
> >
> >
> > Some of this may answer a question Alex raised in an earlier email this
> > morning regarding using the kinematic fitter for PID.
> >
> > Matt
> >
> >
> > On Fri, Mar 21, 2008 at 10:47 AM, Eugene Chudakov <gen@jlab.org> wrote:
> >
> > > Matt,
> > >
> > > I am going to include a slide on the kinem. fitting with the something
> > > like:
> > > - 3-C fit improves the track resolutions
> > > - kin. fitting allows a considerable improvement in identification of
> > > events with kaons over simple kin. constraints.
> > > - the results depend on prominance of backrounds which are flat
> > > or non-Gaussian in the residual space.
> > > - in the ideal case a strong possible suppression can been obtained
> > > - the work is in progress
> > >
> > > You may send me a few statements (items) you would like to make.
> > > Also, you may include a plot. Will you do it?
> > >
> > > Yesterday, I tried the 3-C fit, using the event 3-momentum. It gave me
> > > some additional
> > > BG reduction, a factor of 2 perhaps, with simple cuts and without
> > > a signal suppression. I will look further into it.
> > >
> > > BTW, what improvement in track momentum resolution did you obtain with the
> > > 3-momentum fit? For p2K3pi events I get on average 2.4%-->2.0% - not that
> > > much.
> > > I assumed the diagonal covariance matrix for p,theta,phi.
> > > The energy residual becomes very narrow for "true" events,
> > > so adding the 4-th fit should not change the track resolution.
> > >
> > >
> > > ------------------------------------------------------
> > > Eugene Chudakov
> > > http://www.jlab.org/~gen <http://www.jlab.org/%7Egen>
> > > phone (757) 269 6959 fax (757) 269 5703
> > > Thomas Jefferson National Accelerator Facility
> > > 12000 Jefferson Ave, Newport News, VA 23606 USA
> > >
> > >
> > >
> >
> >
> > --
> > --
> > ----------------------------
> > Matt Bellis
> > Carnegie Mellon University
> > (office) 412-268-6949
> > (cell) 412-310-4586
> > ----------------------------
> >
>
--
Professor Curtis A. Meyer Department of Physics
Phone: (412) 268-2745 Carnegie Mellon University
Fax: (412) 681-0648 Pittsburgh PA 15213-3890
cmeyer@ernest.phys.cmu.edu http://www.curtismeyer.com/