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Re: updated talk for PID



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
>> ----------------------------
>>
>