Constraints on the Minimal Supergravity Model and Prospects for SUSY Particle Production at Future Linear e^+ e^- Colliders

Abstract

We perform a complete analysis of the supersymmetric particle spectrum in the Minimal Supergravity (mSUGRA) model where the soft SUSY breaking scalar masses, gaugino masses and trilinear couplings are unified at the GUT scale, so that the electroweak symmetry is broken radiatively. We show that the present constraints on the Higgs boson and superparticle masses from collider searches and precision measurements still allow for large regions of the mSUGRA parameter space where charginos, neutralinos, sleptons and top squarks as well as the heavier Higgs particles, are light enough to be produced at the next generation of $\ee$ linear colliders with center of mass energy around $\sqrt{s} \sim 800$ GeV, with sizeable cross sections. An important part of this parameter space remains even when we require that the density of the lightest neutralinos left over from the Big Bang, which we calculate using standard assumptions, falls in the range favored by current determinations of the Dark Matter density in the Universe. Already at a c.m. energy of 500 GeV, SUSY particles can be accessible in some parameter range, and if the energy is increased to $\sqrt{s} \simeq 1.2$ TeV, the $e^+e^-$ collider will have a reach for high precision studies of SUSY particles in a range that is comparable to the discovery range of the LHC.

Figures (17)

• Figure 1: Constraints on the $(m_{1/2}, m_0)$ mSUGRA plane. Top--Left: individual constraints from non--convergent $\mu$ (yellow region), tachyonic $M_A$ (green), tachyonic sfermions (blue), light sfermions (dark), light charginos (brown), $\tilde{\chi}_1^0$ non--LSP (light blue), BR($b \to s \gamma)$ (medium grey) and light $h$ boson (light and medium grey). The three other plots are for the $1\sigma$ (dark colors) and $2\sigma$ (light colors) "evidence" for, the Higgs boson (but with larger error bars, Top--Right), $(g_\mu-2)$ (Bottom--Left) and the Dark Matter (Bottom--Right).
• Figure 2: Constraints on the $(m_{1/2}, m_0)$ mSUGRA plane for $\tan \beta = 40$, $A_0=0$ and sign$(\mu)>0$. The grey areas are those excluded by the requirement of EWSB breaking and limits on SUSY particle masses (darker grey), BR($b \to s \gamma)$ (medium grey) and $M_h > 113$ GeV (light and medium grey). The colors are for the "evidence" for the Higgs boson (red), the $(g_\mu-2)$ (blue) and Dark Matter (green).
• Figure 3: Constraints on the $(m_{1/2}, m_0)$ mSUGRA plane for values of $\tan \beta <40$, $A_0=0$ or -1 TeV and sign$(\mu)>0$. The grey areas are those excluded by the requirement of EWSB breaking and limits on SUSY particle masses (darker grey), BR($b \to s \gamma)$ (medium grey) and $M_h > 113$ GeV (light and medium grey). The colors are for the "evidence" for the Higgs boson (red), $(g_\mu-2)$ (blue) and Dark Matter (green).
• Figure 5: Constraints on the $(m_{1/2}, m_0)$ mSUGRA plane for $\tan \beta =40$, $A_0=0$, sign$(\mu)>0$ and different values of the pole top quark mass $M_t$ and $\overline{\rm MS}$ bottom quark mass. The notation is as in Fig. 2.
• Figure 6: Constraints on the $(m_{1/2}, m_0)$ mSUGRA plane for $\tan \beta =40$, $A_0=0$, sign$(\mu)>0$ with different choices of the EWSB scale. The notation is as in Fig. 2