[Halld-physics] J/psi photoproduction simulation using bggen

[Eugene Chudakov]

Hello,

I modified "bggen", adding a possibility to simulate binary reactions
as gamma+p-->A+B, assuming a exp(t*a) t-dependence and an arbitrary
energy dependence. The t-slope and a cross-section table can be set in
the FFREAD input file. For the J/psi, I used a model by Brodsky et al
(PL 2001), with the normalization fit to the data at higher
energies. There is a new tool compiled "xsec_pri" which prints a table
of the cross sections which can be pasted into the FFREAD file. At the
moment it does it for the J/psi only, but it can be extended. A more
detailed description can be found in the README file.

In the directory bggen/run one can find a new file run_jpsi.ffr to be
used for J/psi simulation. The bggen output is the same as
before. Also, at the beginning the program prints the J/psi production
rate in Hz (for the regular diamond radiator and 2uA, equivalent to a
100MHz photon beam in 8.4<E<9.0GeV).

I also added an option to use only the incoherent Bremsstahlung by
setting the peak energy EPEAK to 0. In the Richard's code used 
for simulation I noticed a comment that the incoherent flux might be a
15% off - at the moment it is not critical.  Simulating an amorphous
radiator with a 5mm diameter collimator can be done by "moving" the
radiator closer to the collimator: ZCOLLIM 7600.  ==> ZCOLLIM 5320.

bggen produces a histogram file bggen.his. One can check the
histograms 9001, 9010 and 9011 which show the energy dependence of the
photon flux times the cross section, the flux and the cross section.

The changes have been committed to the repositiory.  After you update
the bggen from the repository and recompile it, you can use the
executable both for the old background simulation and for the J/psi or
other reactions.

Regards,
Eugene

PS. I have not run HDGEANT on the output, just checked the output
ntuple.

------------------------------------------------------
Eugene Chudakov
phone (757) 269 6959  fax (757) 269 6331
Thomas Jefferson National Accelerator Facility
12000 Jefferson Ave,
Newport News, VA 23606 USA

On Wed, 24 Oct 2012, Amiran Tomaradze wrote:

> Dear Evgene,
>
> We received your email below. Thanks for that.
>
> We made some progress in generating of the background Monte-Carlo
> samples using GlueX generic Monte-Carlo code.
> At some point, pretty soon, we want to run signal Monte Carlo(s)
> you mentioned to help with.
>
> Are there any problems to run these, maybe we can help somehow ?
> Thank you for your time !
>
> Best regards, Amiran.
>
>
> On Thu, 18 Oct 2012, Eugene Chudakov wrote:
>
>> Dear Amiran,
>> 
>> I am glad to know that the Northwestern University group is interested
>> in the J/Psi production at threshold. For the J/Psi generator, I used
>> 2 production models, fit to the data at higher energies.  I will
>> assemble a standalone package and send it to you by Monday.
>> 
>> Best regards,
>> Eugene
>> 
>> ------------------------------------------------------
>> Eugene Chudakov
>> phone (757) 269 6959  fax (757) 269 6331
>> Thomas Jefferson National Accelerator Facility
>> 12000 Jefferson Ave,
>> Newport News, VA 23606 USA
>> 
>> On Thu, 18 Oct 2012, Amiran Tomaradze wrote:
>> 
>>> Dear Evgene,
>>> 
>>> Our group from the Northwestern University (Evanston, Illinois)
>>> intends to join the GlueX Collaboration. Our group leader Kamal Seth
>>> was in communications with Curtis Meyer and Matt Shepherd.
>>> We intend to contribute to the GlueX software as service work,
>>> as we have some expertise and resources in that area, and our
>>> physics interest is in studying J/psi photoproduction.
>>> 
>>> Curtis and Matt pointed out that you are the expert on the threshold
>>> J/psi production in Hall D, so we hope that we could work with you,
>>> both for the benefit of our interests and of GlueX as a whole.
>>> 
>>> To develop our proposal for joining the GlueX Collaboration we of course
>>> need to do simulation work using GlueX software. Sean Dobbs (who is our
>>> post-doc) has made some progress in compiling and running the GlueX
>>> reconstruction software.
>>> Our question at present is if you have a realistic Monte-Carlo
>>> event generation code for the J/psi threshold production to share with us,
>>> so we can try to develop the relevant analysis.
>>> 
>>> Any of your suggestions/comments are very welcome.
>>> 
>>> Amiran.
>>> 
>>> 
>>> -----------------
>>> Amiran Tomaradze
>>> Research Associate Professor, Department of Physics and Astronomy
>>> Northwestern University, Evanston, IL60208
>>> Tel: (847) 414 0208
>>> 
>>> 
>> 
>> LocalWords:  stadalone
>> 
>