SUSY GUTs with Yukawa unification: A go/no-go study using FCNC processes

We address the viability of exact Yukawa unification in the context of general SUSY GUTs with universal soft-breaking sfermion and gaugino mass terms at the GUT scale. We find that this possibility is challenged, unless the squark spectrum is pushed well above the limits allowed by naturalness. This conclusion is assessed through a global fit using electroweak observables and quark flavour-changing neutral current (FCNC) processes. The problem is mostly the impossibility of accommodating simultaneously the bottom mass and the BR(B→Xsγ)$\mathrm{BR}(B\to X_s\gamma )$, after the stringent CDF upper bound on the decay Bs→μ⁺μ⁻$B_s\to {\mu }^{+}{\mu }^{-}$ is taken into account, and under the basic assumption that the b→sγ$b\to s\gamma$ amplitude have like sign with respect to the Standard Model one, as indicated by the B→Xs?⁺?⁻$B\to X_s{?}^{+}{?}^{-}$ data.     

A complete analysis of FCNC and CP constraints in general SUSY extensions of the standard model

We analyze the full set of constraints on gluino- and photino-mediated SUSY contributions to FCNC and CP violating phenomena. We use the mass insertion method, hence providing a model-independent parameterization which can be readily applied in testing extensions of the MSSM. In addition to clarifying controversial points in the literature, we provide a more exhaustive analysis of the CP constraints, in particular concerning ε′/ε. As physically meaningful applications of our analysis, we study the implications in SUSY-GUT's and effective supergravities with flavour nonuniversality. This allows us to detail the domain of applicability and the correct procedure of implementation of the FC mass insertion approach.     

A scenario for SUSY QCD

The following scenario is proposed for supersymmetric QCD: With massless (s) quarks, there is a continuum of vacua, including one with all global symmetries unbroken; with (s) quarks of mass m, there is a unique vacuum, no Goldstone bosons, but a rich spectrum of scalars and fermions of mass O(m). Consistency with various non-perturbative requirements is exhibited.     

Decompositions of superfields inD=4 conformal SUSY

We use character formulae for the positive-energy unitary irreducible representations of theN-extendedD=4 conformal superalgebras su(2, 2/N) that were derived earlier to give decompositions of long superfields as they descend to the unitarity threshold.     

FCNC top quark decays in extra dimensions

The flavor changing neutral top quark decay t→cX is computed, where X is a neutral standard model particle, in an extended model with a single extra dimension. The cases for the photon, X=γ, and a standard model Higgs boson, X=H, are analyzed in detail in a non-linear R_ξ gauge. We find that the branching ratios can be enhanced by the dynamics originating in the extra dimension. In the limit where 1/R≫m_t, we have found Br(t→cγ)≃10^-10 for 1/R = 0.5 TeV. For the decay t→cH, we have found Br(t→cH)≃10^-10 for a low Higgs mass value. The branching ratios go to zero when 1/R→∞.     

Dynamics of localized states in N = 4 SUSY QM

A consistent approach is offered for investigating the temporal dynamics of localized states. It is based on exactly solvable quantum mechanical models with multi-well potentials and the associate propagators. The Hamiltonian states with multi-well potentials form an adequate basis for expanding wave packets (WP) of various types and degrees of localization. Special features of WP tunneling have been studied with due regard for all Hamiltonian states with symmetric and asymmetric potentials.     

SUSY at the LHC

I discuss part of the program of work towards discoveries at the LHC with seeds for orientation and navigation in the parameter space given an anticipated multitude of excesses at start-up.     

Looking for SUSY with EDELWEISS-I and-II

The latest results obtained by the EDELWEISS WIMP (weakly interacting massive particles) direct detection experiment using three heat-and-ionization 320-g germanium bolometers are given. Presently the most sensitive WIMP direct detection experiment for WIMP mass >30 GeV, EDELWEISSI is testing a first region of SUSY models compatible with accelerator constraints. The status and main characteristics of EDELWEISS-II, involving in a first stage 28 germanium bolometers and able to accommodate up to 120 detectors, are briefly presented, together with neutron background estimates.     

A Positive Mass Theorem for Spaces with Asymptotic SUSY Compactification

We prove a positive mass theorem for spaces which asymptotically approach a flat Euclidean space times a Calabi-Yau manifold (or any special honolomy manifold except the quaternionic Kähler). This is motivated by the very recent work of Hertog-Horowitz-Maeda [HHM].     

SUSY GUT with automatic doublet-triplet hierarchy

A mechanism is suggested to resolve the problem of doublet-triplet hierarchy in the SU(5) SUSY GUT. In this mechanism, which we call “GIFT” (“Goldstones instead of fine tuning”), the doublets are pseudo-Goldstone bosons of a certain broken global symmetry of the superpotential. With supergravity as the source of SUSY breaking we show that the SU(2)_L×U(1)_Y→U(1)_em breaking as well as the mass of the lightest Higgs boson are due to the radiative corrections.     

Search for SUSY in the AMSB scenario with the DELPHI detector

The DELPHI experiment at the LEP e ⁺ e^- collider collected almost 700 pb^-1 at centre-of-mass energies above the Z⁰ mass pole and up to 208 GeV. Those data were used to search for SUSY in the Anomaly Mediated SUSY Breaking (AMSB) scenario with a flavour independent common sfermion mass parameter. The searches covered several possible signatures experimentally accessible at LEP, with either the neutralino, the sneutrino or the stau being the Lightest Supersymmetric Particle (LSP). They included: the search for nearly mass-degenerate chargino and neutralino, which is a typical feature of AMSB; the search for Standard-Model-like or invisibly decaying Higgs boson; the search for stable staus; the search for cascade decays of SUSY particles resulting in the LSP and a low multiplicity final state containing neutrinos. No evidence of a signal was found, and thus constraints were set in the space of the parameters of the model.Received: 3 September 2003, Revised: 3 February 2004, Published online: 9 March 2004     

A generalized positive energy theorem for spaces with asymptotic SUSY compactification

In this short note, we prove a generalized positive energy theorem for spaces with asymptotic SUSY compactification involving non-symmetric data. This work is motivated by the work of Dai [A positive mass theorem for spaces with asymptotic SUSY compactification, Comm. Math. Phys. 244 (2004) 335–345; A note on positive energy theorem for spaces with asymptotic SUSY compactification, 2004. arXiv:math-ph/0406006], Hertog–Horowitz–Maeda [Negative energy density in Calabi–Yau compactifications, JHEP 0305 (2003) 060], and Zhang [Angular momentum and positive mass theorem, Comm. Math. Phys. 206 (1999) 137–155].     

Multiboson signals in the UN2HDM

The European Physical Journal C - We investigate the Casimir force for parallel plates at finite temperature in the Horava–Lifshitz (HL) theory. We find that the HL exponent cannot be chosen...     

MSSM curvaton in the gauge-mediated SUSY breaking

We study the curvaton scenario using the MSSM flat directions in the gauge-mediated SUSY breaking model. We find that the fluctuations in the both radial and phase directions can be responsible for the density perturbations in the universe through the curvaton mechanism. Although it has been considered difficult to have a successful curvaton scenario with the use of those flat directions, it is overcome by taking account of the finite temperature effects, which induce a negative thermal logarithmic term in the effective potential of the flat direction.