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Re: updated talk for PID
Hall D PID Mail List:
Hi Matt --
your study is indeed very useful, and getting the kinematic fitting
going was a very important step. I think the concern at this point is
to be careful not to "over sale" it, but to make sure we get in the fact
that it really will improve things.
thanks -- Curtis
On Wed March 19 2008, Matt wrote:
> Hi all,
>
> The results from the pi/K separation study I did were never meant to
> imply that we do not need additional PID. And every time I presented these
> results I have emphasized that there is other background that was not
> considered that could leak in. Also, that we are working from an idealized
> case where all tracks are reconstructed (4-C fit) and the errors are known
> perfectly.
>
> The goal was to show what we start with in an ideal world and go from
> there. That's where most of these types of studies start. I completely agree
> that in the real world we will never see quite that performance.
>
> However, I feel that Eugene's talk completely neglects a huge amount of
> effort that has gone into developing a legitimate kinematic fitter and other
> PID tools. If the goal of these talks is to present to the review committee
> where we stand, then we are selling ourselves short by not discussing this
> other work. The kinematic fitter that Eugene mentions is, by his own
> admission, not a fully functioning fitter....though there is one which we
> have checked into our repository and which has been used by both myself and
> the IU group (for 2-photon fits).
>
> I hope that no one feels that my study was presented disingenuously. I
> have always tried to stress the limitations of what I have done just as
> much, if not more so, than whatever results I have shown. I think the fact
> that we have started to incorporate timing information as part of our global
> event fitting is a *huge* step forward....even for perfect world cases and
> it shows where we plan to go for PID.
>
> I am just concerned that Eugene's talk misses out on at least mentioning
> where some of our efforts have been and paints a more pessimistic view of
> the situation than may actually be.
>
>
> Matt
>
>
>
> On Wed, Mar 19, 2008 at 5:54 PM, Matthew Shepherd <mashephe@indiana.edu>
> wrote:
>
> >
> > Hi Curtis,
> >
> > I strongly agree with backing off those numbers in the document.
> >
> > My concern is that you are presenting only the good part of the full
> > story. We wouldn't want to give the impression that additional PID is
> > unnecessary because we've already solved the problem with kinematic
> > fitting. There is not enough time to fully understand the rest of the
> > story regarding which backgrounds leak in. I think this means you
> > should avoid such quantitative statements in the text.
> >
> > Perhaps there are less provocative aspects of Matt's work that could
> > be presented to demonstrate it is something we are hard at work it?
> > Showing nearly perfect signal purity with 50% efficiency in the "key
> > channel for strangeonium hybrids" would be great ammo for shooting
> > down any claim we need supplementary PID.
> >
> > -Matt
> >
> >
> > On Mar 19, 2008, at 5:47 PM, Curtis A. Meyer wrote:
> >
> > > 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 <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
> > >>>
> > >>> 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>
> > <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/
> >
> >
>
>
> --
--
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/