Top squarks and bottom squarks in the minimal supersymmetric standard model with complex parameters

Abstract

We present a phenomenological study of top squarks $({t}_{1,2})$ and bottom squarks $({b}_{1,2})$ in the minimal supersymmetric standard model (MSSM) with complex parameters ${A}_{t},{A}_{b},\ensuremath{\mu},$ and ${M}_{1}.$ In particular we focus on the CP phase dependence of the branching ratios of ${t}_{1,2}$ and ${b}_{1,2}$ decays. We give the formulas of the two-body decay widths and present numerical results. We find that the effect of the phases on the ${t}_{1,2}$ and ${b}_{1,2}$ decays can be quite significant in a large region of the MSSM parameter space. This could have important implications for ${t}_{1,2}$ and ${b}_{1,2}$ searches and the MSSM parameter determination in future collider experiments. We have also estimated the accuracy expected in the determination of the parameters of ${t}_{i}$ and ${b}_{i}$ by a global fit of the measured masses, decay branching ratios, and production cross sections at ${e}^{+}{e}^{\ensuremath{-}}$ linear colliders with polarized beams. Analyzing two scenarios, we find that the fundamental parameters apart from ${A}_{t}$ and ${A}_{b}$ can be determined with errors of 1% to 2%, assuming an integrated luminosity of $1{\mathrm{ab}}^{\ensuremath{-}1}$ and a sufficiently large center of mass system (c.m.s.) energy to produce also the heavier ${t}_{2}$ and ${b}_{2}$ states. The parameter ${A}_{t}$ can be determined with an error of 2--3%, whereas the error on ${A}_{b}$ is likely to be of the order of 50%.