Re: Fwd: Kfit with timing

[Alex Dzierba <dzierba@indiana.edu>]

Title: Re: Fwd: Kfit with timing

Hi Matt (B)

I'll take a look at your note either later today or early tomorrow

morning.  I had also been following some of your earlier exchanges

with Matt S.  My concern is, I'm sure shared by you,   that

we don't give the impression that we can compromise on

charged and neutral particle detection and three momentum

reconstruction and PID because we can employ kinematic fitting.

That will be another tool we need to identify signal over background

and have final four-vectors with which to do the analysis.

On a somewhat related note -- if we have a 4pi p final state with

a cross section that is 10 x that for 2pi2K p (see Table 6) in the

overview document - how effectively does kinematic fitting remove

the latter reaction as a 10% background contribution for the former

without PID info except for TOF in the forward direction.  Another

way to put it is how well can we insure "pion purity".  Do you have

a feel for this?   You can imagine a resonant structure in the latter

reaction showing up as a 10% or so signal in the former as a

false peak after a PWA.

Maybe Eugene has an idea about this?

Cheers

Alex

At 2:51 PM -0400 3/22/08, 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
> > 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

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~