Description

Sartre 1 is an event generator for exclusive diffractive vector meson production and DVCS in ep and eA collisions based on the dipole model. It describes the process: e p → e' p' V and e A → e' A' V where V = J/ψ, φ, ρ, γ. Sartre is not a stand-alone program but a set of C++ classes and C functions that form the API. The heart of Sartre is an implementation of the bSat and bCGC dipole models. We extended the models to also describe eA collisions making Sartre the first generator to describe this class of processes. Saturation is introduced in the bSat model through an exponential term in the scattering amplitude. In order to study the impact of saturation on the production cross-section we also construct a non-saturated version of the bSat model, bNonSat, by linearizing the dipole cross-section.

Sartre was developed at Brookhaven National Laboratory for studies of electron-ion collisions at future facilities such as EIC (eRHIC/JLEIC) and LHeC.

The latest version available for download is Sartre 1.33 superseeding the previous release version 1.22. The latest version now includes UPC collisions, although this should be considered experimental for now (for tables ask the authors). Included now is also the possibility of ϒ production and most importantly a new set of IPSat/bSat and IPNonSat/bNonSat parameters named HMPZ derived from a new fit to combined HERA data. Only ep tables are available for the HMPZ set. KMW will remain the standard until eA tables are created. The calculation of α_s was revised as well as the DGLAP calculation. The v.1.33 tar ball is rather large (~2 GB) due to the many tables that are included. Outstanding tasks are (i) production of ePb tables with new parameter set and (ii) adding density fluctuations.

Version 2 is a long term project with the objective to add inclusive event generation. This will be a major re-write.

The latest version (svn trunk) is not fully tested and we urge users to stick to the latest release v1.33.

License

Sartre is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation. This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose. See the GNU General Public License for more details.