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\title{The first VEGAS-free, exact, 5D, polarized photon-to-e+e-pair conversion event generator
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\author{\speaker{Denis Bernard}\\
        LLR, Ecole Polytechnique AuthorAffiliationamp; CNRS/IN2P3
 \\
        E-mail: \email{denis.bernard@in2p3.fr
}}

%\author{Another Author\\
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\abstract{
  Current pair-conversion event generators, e.g. in geant4, don't sample the five-dimensional differential crosssection (5D DCS), but a product of 1D DCSs. Most of them use high-energy and/or small angle approximations. Also the e+ and e- polar angles are generated independently so energy-momentum is not conserved.
None of them  can simulate the conversion of polarized photons correctly (Astropart.Phys.88 (2017) 60).

I have written a generator that is sampling exactly the 5D Bethe-Heitler DCS [NIM A 729 (2013) 765]. 
I use the VEGAS method: at a given energy, for a given target nucleus, after a 5D grid has been optimized, the DCS is tabulated, something that needs several seconds.
Then I can generate zillions of conversions quickly at that energy and for that target.
The polarization properties  were characterized in Astropart.Phys.88 (2017) 30, especially at low energy where most of the statistics is for cosmic sources.

I have developed a VEGAS-free version that allows the fast generation of the conversion of a photon of a given energy on a given target, with the same other properties as for the VEGAS-based generator.
}

\FullConference{7th Fermi Symposium 2017\\
		15-20 October 2017\\
		Garmisch-Partenkirchen, Germany}


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