No abstract

We consider two potential non-accelerator signatures of generalizations of the well-studied constrained minimal supersymmetric standard model (CMSSM). In one generalization, the universality constraints on soft supersymmetry-breaking parameters are applied at some input scale below the grand unification (GUT) scale , a scenario referred to as ‘sub-GUT’. The other generalization we consider is to retain GUT-scale universality for the squark and slepton masses, but to relax universality for the soft supersymmetry-breaking contributions to the masses of the Higgs doublets. As with other CMSSM-like models, the measured Higgs mass requires supersymmetric particle masses near or beyond the TeV scale. Because of these rather heavy sparticle masses, the embedding of these CMSSM-like models in a minimal SU(5) model of grand unification can yield a proton lifetime consistent with current experimental limits, and may be accessible in existing and future proton decay experiments. Another possible signature of these CMSSM-like models is direct detection of supersymmetric dark matter. The direct dark matter scattering rate is typically below the reach of the LUX-ZEPLIN (LZ) experiment if is close to , but it may lie within its reach if  GeV. Likewise, generalizing the CMSSM to allow non-universal supersymmetry-breaking contributions to the Higgs offers extensive possibilities for models within reach of the LZ experiment that have long proton lifetimes.

We consider the stochastic background of gravitational waves produced by an early generation of Population III stars coupled with a normal mode of star formation at lower redshift.The computation is performed in the framework of hierarchical structure formation and is based on cosmic star formation histories constrained to reproduce the observed star formation rate at redshift z < ∼ 6, the observed chemical abundances in damped Lyman alpha absorbers and in the intergalactic medium, and to allow for an early reionization of the Universe at z ∼ 10 − 20 as indicated by the first year results released by WMAP. We find that the normal mode of star formation produces a gravitational wave background which peaks at 300-500 Hz and is within LIGO III sensitivity. The Population III component peaks at lower frequencies (30-100 Hz depending on the model), and could be detected by LIGO III as well as the planned BBO and DECIGO interferometers.

We consider the possibility that the soft supersymmetry-breaking parameters m 1/2 and m 0 of the MSSM are universal at some scale M in below the supersymmetric grand unification scale M GU T , as might occur in scenarios where either the primordial supersymmetry-breaking mechanism or its communication to the observable sector involve a dynamical scale below M GU T . We analyze the (m 1/2 , m 0 ) planes of such sub-GUT CMSSM models, noting the dependences of phenomenological, experimental and cosmological constraints on M in . In particular, we find that the coannihilation, focus-point and rapid-annihilation funnel regions of the GUT-scale CMSSM approach and merge when M in ∼ 10 12 GeV. We discuss sparticle spectra and the possible sensitivity of LHC measurements to the value of M in .

The apparent discovery of a Higgs boson with mass ∼ 125 GeV has had a significant impact on the constrained minimal supersymmetric extension of the Standard Model in which the scalar masses, gaugino masses and tri-linear A-terms are assumed to be universal at the GUT scale (the CMSSM). Much of the low-mass parameter space in the CMSSM has been excluded by supersymmetric particle searches at the LHC as well as by the Higgs mass measurement and the emergent signal for B s → µ + µ − . Here, we consider the impact of these recent LHC results on several variants of the CMSSM with a primary focus on obtaining a Higgs mass of ∼ 125 GeV. In particular, we consider the one-and two-parameter extensions of the CMSSM with one or both of the Higgs masses set independently of the common sfermion mass, m 0 (the NUHM1,2). We also consider the oneparameter extension of the CMSSM in which the input universality scale M in is below the GUT scale (the sub-GUT CMSSM). We find that when M in < M GU T large regions of parameter space open up where the relic density of neutralinos can successfully account for dark matter with a Higgs boson mass ∼ 125 GeV. In some of these regions essential roles are played by coannihilation processes that are usually less important in the CMSSM with M in = M GU T . Finally, we reconsider mSUGRA models with sub-GUT universality, which have the same number of parameters as the CMSSM. Here too, we find phenomenologically viable regions of parameter space, which are essentially nonexistent in GUT-scale mSUGRA models. Interestingly, we find that the preferred range of the A-term straddles that predicted by the simplest Polonyi model.