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Re: updated talk for PID
Hall D PID Mail List:
Matt,
I intended to come to your results during this week and include them in
the talk. I thought, in fact, that the difference with my simple
calculation would be mainly in the type of background and in 4c
event fitting, optimizing the resolutions etc. I only intended to
check the simple 4-mom. constraint. The PID is another floating subject,
where the TOF resolutions have been recently shifted and the whole thing
was worth being revisited, including the dE/dx.
Reading the 999 paper and your presentations I realized
that the difference is significant and starts, perhaps, at the initial
resolutions. However, the track resolutions I use (taken from David) are
similar or only slightly worse than those you show on page 5 of your
presentation.
Let us consider the reactions you used:
1) gp->pK+pi+K-pi-
2) gp->ppi+pi+pi-pi-
These reactions are identical in the 3-momentum space. The only
difference is the energy. It is a 1-dim. separation.
I obtained the E_final-E_initial resolution of sigma=150 MeV
(180 MeV for some PYTHIA events, perhaps because of a different energy
distribution). The reaction 2), treated as 1) gives an average energy shift
of 120MeV, which is 0.8 sigma of one peak. So, I get a rather small separation...
What are your values for these resolutions/separations?
Thanks,
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 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/
> >
> >
>
>
> --
> --
> ----------------------------
> Matt Bellis
> Carnegie Mellon University
> (office) 412-268-6949
> (cell) 412-310-4586
> ----------------------------
>