[Halld-offline] [Halld-physics] pilot run for pwa: event generation

[Matthew Shepherd]

Hi Craig,

I basically need a function that I can plug some four vectors into and it returns a complex number that equal to the amplitude for the particular reaction.  The function likely has parameters that depend on spin and polarization of various particles in the decay and consists of the correct linear combination of d-functions evaluated with angles in the appropriate frames.  It essentially form "the basis" for the PWA.  GlueX-doc 29 (written by Curtis) is a start -- we should verify, understand, and code this up.  Also, it might be easier to start with something like eta pi in the final state.   In this case, how does the photon polarization manifest itself in the final state angular distributions?

-Matt


On Mar 17, 2010, at 4:31 PM, Craig Bookwalter wrote:

> Hi Matt,
>   Thanks for the quick reply--I'm confused as to what you mean by an `expression' for the amplitudes...can you elaborate?
> 
> Thanks again.
> 
> --cb
> 
> 
> Matthew Shepherd wrote:
>> Hi Craig,
>> 
>> We just about finished with version 1.0 (or 0.1?) of our AmpTools package that will allow both MC generation and fitting.  (In fact, I'm sitting in the BESIII control room writing code right now.)  It will take some time to get together a documented package, but I'm happy to start to work with anyone who wants to use it. 
>> I think what we need most next is the expression for the amplitudes.  I have code to generate all the kinematics.  I've also done some generation with E852 amplitudes (spin 0 beam instead of spin 1).
>> 
>> Once we get the expressions for the amplitudes, things should go pretty quickly.  I was generating and fitting (with E852 amplitudes) just last night.  Using the NVIDIA card on my laptop I was easily able to generate a couple hundred toy data sets with moderate statistics and fit them to examine pull distributions.  With graphics acceleration, this pretty much becomes an interactive task, like fitting a histogram.
>> 
>> If there is a small group of interested people, perhaps we could arrange a PWA powwow around the May mtg. I would be happy to organize a tutorial on the software.  The more that people use it and complain, the faster it will get debugged!
>> 
>> -Matt
>> 
>> 
>> On Mar 17, 2010, at 4:02 PM, Craig Bookwalter wrote:
>> 
>>  
>>> Hi folks,
>>>   Last week at the offline software meeting there was some discussion about attempting a partial-wave analysis with currently existing software and simulated data, both to build some expertise locally at JLab as well as to flesh out where effort needs to be focused in the PWA development. Assuming that the folks at Indiana doing the bulk of this work are in favor of this idea, it seems the first order of business would be to generate some monte carlo with a set of resonances decaying with all the appropriate angular information. I seem to remember Adam Szczepaniak doing something like this for me a few years ago when I first started playing around with the Ruby fitter--does that code still exist? Can we bring it into the GlueX repository?
>>> 
>>> Thanks in advance.
>>> 
>>> --cb
>>> 
>>> -- 
>>> -------------------------------------------------------------------------
>>> Craig Bookwalter			FSU Office:  (850) 644 3808
>>> Department of Physics			JLab Office: (757) 269 5465
>>> Florida State University		craigb at hadron.physics.fsu.edu
>>> Tallahasse, FL 32306			craigb at jlab.org		
>>> 
>>> 
>>> "One toke? You poor fool. Just wait till you see those (expletive) bats."
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>>> 
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>> 
>> 
>>  
> 
> 
> -- 
> -------------------------------------------------------------------------
> Craig Bookwalter			FSU Office:  (850) 644 3808
> Department of Physics			JLab Office: (757) 269 5465
> Florida State University		craigb at hadron.physics.fsu.edu
> Tallahasse, FL 32306			craigb at jlab.org		
> 
> 
> "One toke? You poor fool. Just wait till you see those (expletive) bats."
> -------------------------------------------------------------------------
>