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Manuscript Title: SUSYGEN 2.2, a Monte Carlo event generator for MSSM sparticle production at e+e- colliders.
Authors: S. Katsanevas, P. Morawitz
Program title: SUSYGEN 2.2
Catalogue identifier: ADIG_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 112(1998)227
Programming language: Fortran.
Computer: DEC ALPHA.
Operating system: UNIX, VMS.
RAM: 450K words
Word size: 32
Keywords: Particle physics, Elementary, Event simulation, Electron positron, Collisions, Lep, Minimal supersymmetric, Standard model, R-parity violation, Supergravity, Gauge mediated, Supersymmetry breaking.
Classification: 11.2.

Subprograms used:
Cat Id Title Reference
ACTU_v1_0 PYTHIA 5.7 AND JETSET 7.4 CPC 82(1994)74
ACTA_v1_0 PHOTOS, VERSION 2.0 CPC 79(1994)291

Nature of problem:
The complexity and the interdependence of the MSSM signals demand a fast and precise simulation program which treats the production and decay of all possible sparticles in different models of supersymmetry breaking, and in models in which R-parity is either conserved or violated.

Solution method:
SUSYGEN 2.2 is a Monte Carlo generator for the tree-level production and decay of all MSSM sparticles at e+e- colliders. It includes pair- production of gauginos, sfermions and squarks, the production of a gravitino plus a neutralino in Gauge-mediated SUSY breaking model, the single production of gauginos through s-channel resonance in R-parity violating models, and the production of Higgses. The program implements all important decay modes of sparticles relevant to LEP energies, including cascade decays to lighter SUSY states, radiative decays of gauginos to a photon, decays to the Higgses, decays to gravitinos, and R-parity violating decays to Standard Model particles. The precise matrix elements are used for the production and for the decay of sparticles, though helicity correlations are not taken into account. The mass spectrum of the SUSY particles at the electroweak scale is either calculated assuming a common mass scale at the GUT scale (Supergravity models or Gauge mediated SUSY breaking models), or the mass spectrum can be optionally provided by the user. The LSP can either be the neutralino, the sneutrino or the gravitino in R-parity conserving models, or there can be no LSP in the sense that all sparticles can decay to standard particles through R-parity violation. The initial state radiative corrections take account of pT/pL effects in the Structure Function formalism. QED final state radiation is implemented using the PHOTOS library [1]. An optimised hadronisation interface to JETSET 7.4 [2] is provided, which also takes into account the lifetime of sparticles.

The factorised treatment of the production and decay of sparticles through the appropriate matrix elements is more accurate than the equivalent treatment of generators like e.g. ISAJET [3] and SPYTHIA [4], where the sparticle decays are described by phase space. Nevertheless it is less accurate than programs which take helicity correlations into account, as for example is done in SUSY23 [5], or DFGT [6]. Squark hadronisation before decay is not implemented, and the hadronisation of squark decays via the R-parity violating coupling lambda" is only simulated using the independent fragmentation scheme. The decays to gluinos are at present not implemented. And three-body decays of sfermions to lighter sfermions are not included.

Unusual features:

Running time:
40 events/sec on a DEC ALPHA.

[1] E. Barberio and Z. Was, Comp. Phys. Commun. 79 (1994) 291.
[2] T. Sjostrand, Comp. Phys. Commun. 82 (1994) 74.
[3] F. Paige and S. Protopopescu, in: Supercollider Physics, ed. D. Soper (World Scientific, New York, 1986) p. 41; H. Baer, F. Paige, S. Protopopescu and X. Tata, in the 'Proceedings of the Workshop on Physics at Current Accelerators and the Supercollier', ed. J. Hewett, A. White and D. Zeppenfeld, Argonne National Laboratory Report ANL-HEP-CP-93-92 (1993); and H. Baer, F. Paige, S. Protopopescu and X. Tata, "Simulating Supersymmetry with ISAJET 7.0/ISASUSY 1.0", hep-ph/9305342.
[4] S. Mrenna, Comput. Phys. Commun. 101 (1997) 232.
[5] J. Fujimoto et al., "SUSYX23", in the proceedings of the Workshop 'Physics at LEP 2', eds. G. Altarelli, T. Sjostrand, and F. Zwirner, CERN 96-01, Geneva, 1996, p. 335; and J. Fujimoto et al., "SUSYX23 v2.0: and Event Generator for Supersymmetric Processes at e+e- Colliders", hep-ph/9711283.
[5] C. Dionisi, S. Giagu, K. Fujii, T. Tsukamoto, "DFGT: a chargino MC generator with full spin correlations", in the proceedings of the 'Workshop Physics at LEP 2', eds. G. Altarelli, T. Sjostrand, and F. Zwirner, CERN 96-01, Geneva, 1996, p. 337.