Susygen3, an Event Generator for Linear Colliders

TL;DR

SUSYGEN3 addresses the need for a precision Monte Carlo tool for SUSY studies at linear colliders by incorporating beamstrahlung, beam polarization, spin correlations, and CP-violating phases into event generation across MSSM, MSUGRA, and GMSB frameworks. It extends SUSYGEN2 with CIRCEE beamstrahlung, full spin-correlation via helicity amplitudes, CP phases in the MSSM, and spectrum interfaces to SUSPECT, along with interfaces to PHOTOS, TAUOLA, and JETSET for realistic radiation, decays, and hadronization. Masses are treated exactly with a helicity-amplitude framework, and cross sections can exhibit strong dependence on phases such as $\phi_\mu$ and on parameters like $m_{\tilde{\nu}_e}$ and $\tan\beta$. The resulting tool enhances background suppression and precision parameter extraction, expanding SUSY studies to $e^+e^-$, $e^-p$, and hadronic colliders, thereby enabling more accurate tests of SUSY scenarios at current and future colliders.

Abstract

The Monte Carlo program \texttt{SUSYGEN}, initially designed for computing distributions and generating events for supersymmetric particle production in $e^+e^-$ collisions, has now been upgraded to study supersymmetric processes at linear colliders by the inclusion of beamstrahlung, beam polarization, spin correlations and complex couplings including CP violating phases. It continues to offer, in the new context, the possibility to study the production and decay of supersymmetric particles within the most general minimal standard supersymmetric model (MSSM), the minimal supergravity model (MSUGRA) or the gauge mediated supersymmetry breaking model (GMSB), with or without assuming R-parity conservation.

Figures (2)

• Figure 1: The figure on the left side shows the $d\sigma/d\cos\theta$ distribution for the final $e^-$ associated to the process $e^+e^-\to \tilde{\chi}^0_2\tilde{\chi}^0_1$ with and without taking into account spin correlations. The figure on the right shows the momentum distribution of $e,\mu$ and $\pi$, decay products of $\tau$ produced in the process $e^+e^- \to \tilde{\tau}_1^+ \tilde{\tau}_1^- \to \tau^+ \tilde{\chi}^0_1 \tau^- \tilde{\chi}^0_1$. The distributions have been plotted for two hypotheses concerning the stau mixing angle $\theta_{\tilde{\tau}}$ ($\tilde{\tau}_L$ and $\tilde{\tau}_R$) and compared to the no spin correlation case
• Figure 2: $e^+e^-\to \tilde{\chi}^+_1 \tilde{\chi}^-_1$ cross section evolution in terms of $\phi_\mu$, the phase associated to the higgsino mixing mass parameter $\mu$. We also assume different hypotheses concerning the sneutrino $\tilde{\nu_e}$ mass