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Re: updated talk for PID
Hall D PID Mail List:
Hi Matt (Shepherd),
yes, they do seem to imply that with kinematic fitting and strangeness
conservation, we are done. I do not believe this. I suspect that if we
were to include channels that had hyperons (Lambda, Sigma), and a
single kaon, we would have more problems. I would guess that if we
had a missing neutron (or proton), the 1-C fits would not be nearly
so powerful.
What I take from these is that kinematic fitting will help us a lot
(every experiment I have done has seen this), but even though I
put the numbers in the document, I think I want to back off on this
at the moment until we have a better understanding, or at least
recast Matt Bellis's work as a hypothical??
Opionions anyone?
thanks -- Curtis
On Wed March 19 2008, Matthew Shepherd wrote:
> Hall D PID Mail List:
>
>
> Hi Eugene and Matt,
>
> I was also struck by this passage in the document and the studies that
> Matt did. I don't doubt the power of kinematic fitting, but these
> results are quite surprising. In fact, taken at face value, they
> would say forget any other PID -- we don't need it. For some of the
> high multiplicity all neutral channels we were happy with S:B of about
> 5:1 and 10% efficiency. You have strange channels with S:B = infinity
> and ~50% efficiency -- that's quite good.
>
> I can't help but wonder what the background will be from broken
> events. For example, if you have an event where miss a pion you can
> make another one or two pions in the event a kaon to recover some of
> the lost four momentum.
>
> Matt
>
> On Mar 19, 2008, at 5:25 PM, Eugene Chudakov wrote:
>
> > Hall D PID Mail List:
> >
> > Matt,
> >
> > thanks for sending me your talk on the event fitting.
> > For my current studies I (in fact) did not use any fitting. I just
> > selected particle combinations, balancing the initial and final 3-
> > momentum and
> > the energy. Again, it was very simple: I selected the same absolute
> > cuts
> > in GeV for all events, without calculating the individual
> > covariances for each event.
> > Therefore, there must be a room for improvement.
> > I am sure you have already perfected this method.
> >
> > If I did any new step with this study, it is considering the minimum
> > bias
> > background from PYTHIA.
> > The pion suppression is only a factor of 0.4-0.6 for a kaon candidate,
> > the overall suppression is about 0.2. The proton PID gives another
> > factor of 4.
> > Indeed, a factor of 3 comes from combinatorics, while some events
> > may have
> > no proton as well.
> >
> > Eugene
> >
> > ------------------------------------------------------
> > 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
> >
> > On Wed, 19 Mar 2008, Matt wrote:
> >
> >> Hi Eugene,
> >>
> >> The kinematic fit mentioned in your talk, is that the fitter that I
> >> checked into the repository under $HALLD_HOME/src/libraries/PID? Or a
> >> different one? I see you're doing a different study than what I
> >> did, but I
> >> found that using time-of-flight info from the BCAL and forward TOF
> >> got you
> >> quite far in trying to do kaon physics, though I had a simpler
> >> physics
> >> background than the full pythia spectrum.
> >>
> >> Matt
> >>
> >>
> >> On Wed, Mar 19, 2008 at 3:54 PM, Eugene Chudakov gen <gen@jlab.org>
> >> wrote:
> >>
> >>> Hall D PID Mail List:
> >>>
> >>>
> >>> I updated the slides, including new pictures and adding more info.
> >>>
> >>> It can be found at:
> >>> http://www.jlab.org/~gen/gluex/talk_pid_rev.pdf<http://www.jlab.org/%7Egen/gluex/talk_pid_rev.pdf
> >>> >
> >>>
> >>> The talk source is located at
> >>> jlabl1:/home/gen/tex/GLUEX/talk_pid_march_2008.tex
> >>> The pictures are stored at
> >>> jlabl1:/home/gen/tex/GLUEX/pictures/plot_glx_*.pdf
> >>> For each picture there are also .epsi and .ps files.
> >>>
> >>> Eugene
> >>>
> >>> ----------------------------
> >>> Eugene Chudakov
> >>> JLab
> >>>
> >>>
> >>
> >>
> >> --
> >> --
> >> ----------------------------
> >> 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/