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Re: Fwd: Kfit with timing
Hall D PID Mail List:
I agree completely - this is a good first start but we should
emphasize that this is a start and much more work needs to done.
I still think the result is too good to be true.
In the meantime - I found another BC experiment reported by
a Aachen-CERN-Cracow collaboration - pi+p interactions at 8 GeV
They identify the K+K-pi+p final state by kinematic fitting.
They seem to find more like a 10% feed-through of background.
Alex
At 8:42 AM -0400 3/24/08, Elke-Caroline Aschenauer wrote:
>Hall D PID Mail List:
>
>On Mon, 24 Mar 2008, Alex Dzierba wrote:
>
>Dear all,
>
>I totally agree all the work is very nice.
>The only thing which still worries me a bit is the assumptions on the
>error matrix for the tracking. I think we should show one or 2 example for
>the kinematic fits, but should clearly point out that this is still a
>point of concern.
>
>cheers elke
>
>
>> Date: Mon, 24 Mar 2008 07:17:20 -0400
>> From: Alex Dzierba <dzierba@indiana.edu>
>> To: Eugene Chudakov <gen@jlab.org>
>> Cc: halld-pid@jlab.org, bellis@ernest.phys.cmu.edu,
>> cmeyer@ernest.phys.cmu.edu
>> Subject: Re: Fwd: Kfit with timing
>>
>> Hall D PID Mail List:
>>
>> Dear Eugene, Matt et al
>>
>> Matt indeed did a nice job and I find his results almost too good to
>> be true. But to first order they are consistent with bubble chamber
>> data at these energies.
>>
>> Most of information about photoproduction at 9 GeV comes from a SLAC
>> bubble chamber experiment (Bingham et al, Phys Rev 8 (1973) 1277).
>> They employed kinematic fitting to identify the reactions with 4pi-p
>> final state and 2pi-2K-p final state (in the 5-prong topology) and
>> found these to be in the ratio of 10:1. They were able to identify
>> the proton in the bubble chamber by dE/dx. There was no way to
>> separate pions from Kaons. They did studies to look at how many
>> simulated events had an incorrect kinematic identification. These
>> were not very clearly described in the paper but it seems that the
>> level of misidentification was of order 1%. That same experiment
>> also looked at the 7-prong events and identified the 6pi-p and
>> 4pi-2K-p final states and found these in the ratio 15:1.
>>
>> A note regarding Pythia backgrounds: When I did Pythia studies in
>> September (see GlueX-doc-856) I found that for the 4pi-p and
>> 2pi-2K-p reactions the effective mass distribution for all four
>> mesons in both reactions showed no structure - it rose nearly
>> linearly with mass from threshold and rolled over to zero at the
>> kinematic limit. In the 4pi-p sample there was no structure in the
>> 2pi masses (no rho's) but in the K-pi mass distributions - it seemed
>> to be largely K*(890).
>>
>> Are there 5-prong events with a clearly identified proton in the CLAS
>> data? And have these been analyzed with kinematic fitting and if so
>> what are the results?
>>
>> Cheers
>> Alex
>>
>> >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%.
>> >
>> >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.
>> >
>> >
>> >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
>> >> ----------------------------
>> >>
>>
>>
>> --
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> Alex R. Dzierba
>> Chancellor's Professor of Physics (Emeritus)
>> Department of Physics / Indiana U / Bloomington IN 47405 / 812-855-9421
>> JLab Visiting Fellow
>> Jefferson Lab / 12000 Jefferson Ave / Newport News, VA 23606 / 757-269-7577
>> Home Phone: 812-825-4063 Cell: 812-327-1881 Fax: 866-541-1263
>> http://www.dzre.com/alex
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
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--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Alex R. Dzierba
Chancellor's Professor of Physics (Emeritus)
Department of Physics / Indiana U / Bloomington IN 47405 / 812-855-9421
JLab Visiting Fellow
Jefferson Lab / 12000 Jefferson Ave / Newport News, VA 23606 / 757-269-7577
Home Phone: 812-825-4063 Cell: 812-327-1881 Fax: 866-541-1263
http://www.dzre.com/alex
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~