Yudi Santoso

Exploration of the MSSM with Non-Universal Higgs Masses

We explore the parameter space of the minimal supersymmetric extension of the Standard Model (MSSM), allowing the soft supersymmetry-breaking masses of the Higgs multiplets, m1,2, to be non-universal (NUHM). Compared with the constrained MSSM (CMSSM) in which m1,2 are required to be equal to the soft supersymmetry-breaking masses m0 of the squark and slepton masses, the Higgs mixing parameter μ and the pseudoscalar Higgs mass mA, which are calculated in the CMSSM, are free in the NUHM model. We incorporate accelerator and dark matter constraints in determining allowed regions of the (μ,mA), (μ,M2) and (m1/2,m0) planes for selected choices of the other NUHM parameters. In the examples studied, we find that the LSP mass cannot be reduced far below its limit in the CMSSM, whereas mA may be as small as allowed by LEP for large tanβ. We present in Appendices A–D details of the calculations of neutralino–slepton, chargino–slepton and neutralino–sneutrino coannihilation needed in our exploration of the NUHM.

The MSSM parameter space with non-universal Higgs masses

Abstract Without assuming that Higgs masses have the same values as other scalar masses at the input GUT scale, we combine constraints on the minimal supersymmetric extension of the Standard Model (MSSM) coming from the cold dark matter density with the limits from direct searches at accelerators such as LEP, indirect measurements such as b→sγ decay and the anomalous magnetic moment of the muon. The requirement that Higgs masses-squared be positive at the GUT scale imposes important restrictions on the MSSM parameter space, as does the requirement that the LSP be neutral. We analyze the interplay of these constraints in the (μ,mA), (μ,m1/2), (m1/2,m0) and (mA,tanβ) planes. These exhibit new features not seen in the corresponding planes in the constrained MSSM in which universality is extended to Higgs masses.

Calculations of Neutralino-Stop Coannihilation in the CMSSM

Abstract We present detailed calculations of the χ t 1 coannihilation channels that have the largest impact on the relic χ density in the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which scalar masses m0, gaugino masses m1/2 and the trilinear soft supersymmetry-breaking parameters A0 are each assumed to be universal at some input grand unification scale. The most important t 1 t 1 ∗ and t 1 t 1 annihilation channels are also calculated, as well as t 1 l coannihilation channels. We illustrate the importance of these new coannihilation calculations when A0 is relatively large. While they do not increase the range of m1/2 and hence mχ allowed by cosmology, these coannihilation channels do open up new ‘tails’ of parameter space extending to larger values of m0.

Update on the Direct Detection of Supersymmetric Dark Matter

We compare updated predictions for the elastic scattering of supersymmetric neutralino dark matter with the improved experimental upper limit recently published by Cryogenic Dark Matter Search (CDMS) II. We take into account the possibility that the {pi}-nucleon {sigma} term may be somewhat larger than was previously considered plausible, as may be supported by the masses of exotic baryons reported recently. We also incorporate the new central value of m{sub t}, which affects indirectly constraints on the supersymmetric parameter space, for example, via calculations of the relic density. Even if a large value of {sigma} is assumed, the CDMS II data currently exclude only small parts of the parameter space in the constrained minimal standard model (CMSSM) with universal soft supersymmetry-breaking Higgs, squark, and slepton masses. None of the previously proposed CMSSM benchmark scenarios is excluded for any value of {sigma}, and the CDMS II data do not impinge on the domains of the CMSSM parameter space favored at the 90% confidence level in a recent likelihood analysis. However, some models with nonuniversal Higgs, squark, and slepton masses and neutralino masses < or approx. 700 GeV are excluded by the CDMS II data.

Gravitino dark matter in the CMSSM

We consider the possibility that the gravitino might be the lightest supersymmetric particle (LSP) in the constrained minimal extension of the Standard Model (CMSSM). In this case, the next-to-lightest supersymmetric particle (NSP) would be unstable, with an abundance constrained by the concordance between the observed light-element abundances and those calculated on the basis of the baryon-to-entropy ratio determined using CMB data. We modify and extend previous CMSSM relic neutralino calculations to evaluate the NSP density, also in the case that the NSP is the lighter stau, and show that the constraint from late NSP decays is respected only in a limited region of the CMSSM parameter space. In this region, gravitinos might constitute the dark matter.

Likelihood analysis of the constrained minimal supersymmetric standard model parameter space

We present a likelihood analysis of the parameter space of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which the input scalar masses m0 and fermion masses m1/2 are each assumed to be universal. We include the full experimental likelihood function from the LEP Higgs search as well as the likelihood from a global precision electroweak fit. We also include the likelihoods for b → sγ decay and (optionally) gμ−2. For each of these inputs, both the experimental and theoretical errors are treated. We include the systematic errors stemming from the uncertainties in mt and mb, which are important for delineating the allowed CMSSM parameter space as well as calculating the relic density of supersymmetric particles. We assume that these dominate the cold dark matter density, with a density in the range favoured by WMAP. We display the global likelihood function along cuts in the (m1/2, m0) planes for tan β = 10 and both signs of μ, tanβ = 35, μ < 0 and tanβ = 50, μ > 0, which illustrate the relevance of gμ − 2 and the uncertainty in mt. We also display likelihood contours in the (m1/2, m0) planes for these values of tanβ. The likelihood function is generally larger for μ > 0 than for μ < 0, and smaller in the focus-point region than in the bulk and coannihilation regions, but none of these possibilities can yet be excluded. CERN–TH/2003-262 October 2003

Very constrained minimal supersymmetric standard models

We consider very constrained versions of the minimal supersymmetric extension of the Standard Model (VCMSSMs) which, in addition to constraining the scalar masses m0 and gaugino masses m1/2 to be universal at some input scale, impose relations between the trilinear and bilinear soft supersymmetry breaking parameters A0 and B0. These relations may be linear, as in simple minimal supergravity models, or nonlinear, as in the GiudiceMasiero mechanism for generating the Higgs-mixing µ term. We discuss the application of the electroweak vacuum conditions in VCMSSMs, which may be used to make a prediction � � � = � � � �

On the Feasibility of a Stop NLSP in Gravitino Dark Matter Scenarios

We analyze the possibility that the lighter stop ˜1 could be the next-to-lightest supersymmetric particle (NLSP) in models where the gravitino is the lightest supersymmetric particle (LSP). We do not find any possibility for a stop NLSP in the constrained MSSM with universal input soft supersymmetry-breaking masses at the GUT scale (CMSSM), but do find small allowed regions in models with non-universal Higgs masses (NUHM). We discuss the cosmological evolution of stop hadrons. Most ˜1qq ‘sbaryons’ and the corresponding ‘antisbaryons’ annihilate with conventional antibaryons and baryons into ˜1¯ q ‘mesinos’ and the corresponding ‘antimesinos’, respectively, shortly after the quark-hadron transition in the early Universe, and most mesinos and antimesinos subsequently annihilate. As a result, insufficient metastable charged stop hadrons survive to alter Big Bang nucleosynthesis. CERN-PH-TH/2007-003

Phenomenological constraints on patterns of supersymmetry breaking

Specic models of supersymmetry breaking predict relations between the trilinear and bilinear soft supersymmetry breaking parameters A0 and B0 at the input scale. In such models, the value of tan can be calculated as a function of the scalar masses m0 and the gaugino masses m1=2, which we assume to be universal. The experimental constraints on sparticle and Higgs masses, b ! s decay and the cold dark matter density CDMh 2 can then be used to constrain tan in such specic models of supersymmetry breaking. In the simplest Polonyi model with A0 =( 3 p 3)m0 = B0 + m0, we nd 11 0( 0, and the range 1:25 < A0=m0 < 4:8 for <0. In these models, we nd no solutions in the rapid-annihilation ‘funnels’ or in the ‘focus-point’ region. We also discuss the allowed range of tan in the no-scale model with A0 = B0 =0 . In all these models, most of the allowed regions are in the ~ 1 coannihilation ‘tail’.

CP-odd Phase Correlations and Electric Dipole Moments

We revisit the constraints imposed by electric dipole moments (EDMs) of nucleons and heavy atoms on new CP-violating sources within supersymmetric theories. We point out that certain two-loop renormalization group corrections induce significant mixing between the basis-invariant CP-odd phases. In the framework of the constrained minimal supersymmetric standard model (CMSSM), the CP-odd invariant related to the soft trilinear A-phase at the GUT scale, θA, induces non-trivial and distinct CP-odd phases for the three gaugino masses at the weak scale. The latter give one-loop contributions to EDMs enhanced by tan β, and can provide the dominant contribution to the electron EDM induced by θA. We perform a detailed analysis of the EDM constraints within the CMSSM, exhibiting the reach, in terms of sparticle spectra, which may be obtained assuming generic phases, as well as the limits on the CP-odd phases for some specific parameter points where detailed phenomenological studies are available. We also illustrate how this reach will expand with results from the next generation of experiments which are currently in development.