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Re: updated talk for PID
Hall D PID Mail List:
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
>>> 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/