Likelihood analysis of the minimal AMSB model

Abstract

We perform a likelihood analysis of the minimal anomaly-mediated supersymmetry-breaking (mAMSB) model using constraints from cosmology and accelerator experiments. We find that either a wino-like or a Higgsino-like neutralino LSP, tilde{chi }^0_{1}, may provide the cold dark matter (DM), both with similar likelihoods. The upper limit on the DM density from Planck and other experiments enforces m_{tilde{chi }^0_{1}} lesssim 3 ,, mathrm {TeV} after the inclusion of Sommerfeld enhancement in its annihilations. If most of the cold DM density is provided by the tilde{chi }^0_{1}, the measured value of the Higgs mass favours a limited range of tan beta sim 5 (and also for tan beta sim 45 if mu > 0) but the scalar mass m_0 is poorly constrained. In the wino-LSP case, m_{3/2} is constrained to about 900,, mathrm {TeV} and m_{tilde{chi }^0_{1}} to 2.9pm 0.1,, mathrm {TeV}, whereas in the Higgsino-LSP case m_{3/2} has just a lower limit gtrsim 650,, mathrm {TeV} (gtrsim 480,, mathrm {TeV}) and m_{tilde{chi }^0_{1}} is constrained to 1.12 ~(1.13) pm 0.02,, mathrm {TeV} in the mu >0 (mu <0) scenario. In neither case can the anomalous magnetic moment of the muon, (g-2)_mu , be improved significantly relative to its Standard Model (SM) value, nor do flavour measurements constrain the model significantly, and there are poor prospects for discovering supersymmetric particles at the LHC, though there are some prospects for direct DM detection. On the other hand, if the tilde{chi }^0_{1} contributes only a fraction of the cold DM density, future LHC -based searches for gluinos, squarks and heavier chargino and neutralino states as well as disappearing track searches in the wino-like LSP region will be relevant, and interference effects enable mathrm{BR}(B_{s, d} rightarrow mu ^+mu ^-) to agree with the data better than in the SM in the case of wino-like DM with mu > 0.