Can supersymmetry solve the strong CP-violation problem?

We present evidence that supersymmetry can help to solve the strong CP-violation problem. This evidence is based on the observation that the θ-vacuum in supersymmetry unbroken gauge theories is a CP-invariant. We also point out that the complicated vacua structure in supersymmetrical gauge models cannot lead itself to supersymmetry breaking.     

On the penguin phases and missing CP asymmetries in exclusive hadronic B decays

Within the standard model, we elucidate the picture of exclusive hadronic B-meson decays, which occur through both the tree and penguin channels. We emphasize that the weak penguin phase is entangled with the strong one and they can be parted only in special approximation. Ignoring this point will lead to significant missing of direct CP violation in either charged-B or neutral-B decays. The effects of these phases on CP-violating partial rate asymmetries are examined, and the relevant ambiguities in the previous literature are clarified.     

CP violation induced by heavy Majorana neutrinos in the decays of Higgs scalars into top-quark, W - and Z-boson pairs

We analyze the possibility of CP violation induced by heavy Majorana neutrinos in the decays of the Higgs particle into top-quark, W - and Z-boson pairs. In the framework of various “see-saw” models with interfamily mixings, we find that Majorana neutrinos may give rise to sizable CP-odd observables at the one-loop electroweak order. Numerical estimates of these CP-violating effects that may be detected in high-energy colliders are presented.     

CP violation in multi-Higgs supersymmetric models

We consider supersymmetric extensions of the standard model with two pairs of Higgs doublets. We study the possibility of spontaneous CP violation in these scenarios and present a model where the origin of CP violation is soft, with all the complex phases in the Lagrangian derived from complex masses and vacuum expectation values (VEVs) of the Higgs fields. The main ingredient of the model is an approximate global symmetry, which determines the order of magnitude of Yukawa couplings and scalar VEVs. We assume that the terms violating this symmetry are suppressed by powers of the small parameter ε_PQ = O(m_b/m_t). The tree-level flavor-changing interactions are small due to a combination of this global symmetry and a flavor symmetry, but they can be the dominant source of CP violation. All CP-violating effects occur at order ε_PQ² as the result of exchange of almost decoupled extra Higgs bosons and/or through the usual mechanisms with an almost real CKM matrix. On dimensional grounds, the model gives ε_K ≈ ε_PQ² and predicts for the neutron electric dipole moment (and possibly also for ε_K¹) a suppression of order ε_PQ² with respect to the values obtained in standard and minimal supersymmetric scenarios. The predicted CP asymmetries in B decays are generically too small to be seen in the near future. The mass of the lightest neutral scalar, the strong CP problem, and possible contributions to the Z decay into b quarks (the R_b puzzle) are also briefly addressed in the framework of this model.     

The supersymmetric Ward identities on the lattice

Supersymmetric (SUSY) Ward identities are considered for the N=1 SU(2) SUSY Yang-Mills theory discretized on the lattice with Wilson fermions (gluinos). They are used in order to compute non-perturbatively a subtracted gluino mass and the mixing coefficient of the SUSY current. The computations were performed at gauge coupling and hopping parameter , 0.194, 0.1955 using the two-step multi-bosonic dynamical-fermion algorithm. Our results are consistent with a scenario where the Ward identities are satisfied up to O(a) effects. The vanishing of the gluino mass occurs at a value of the hopping parameter which is not fully consistent with the estimate based on the chiral phase transition. This suggests that, although SUSY restoration appears to occur close to the continuum limit of the lattice theory, the results are still affected by significant systematic effects. Received: 8 November 2001 / Revised version: 14 January 2001 / Published online: 15 March 2002     

Magnetic quadrupole moment of W-boson in Kobayashi-Maskawa model

Due to CP-invariance violation a vector particle can acquire a T- and P-odd electric dipole moment and a magnetic quadrupole one. The W-boson magnetic quadrupole moment is calculated in the Kobayashi-Maskawa model. This is the only known CP-odd moment arising in this model in two-loop approximation.     

The self-dual Chern-Simons CP(N) models

We study the Chern-Simons CP(N) models with a global U(1) symmetry and found the self-dual models among them. The Bogomolnyi-type bound in these self-dual models is a nontrivial generalization of that in the pure CP(N) models. Our models have quite a rich vacuum and soliton structure and approach the many known gauged self-dual models in an appropriate limit.     

Implications of a 17 keV neutrino for baryogenesis

There is some experimental evidence for a 17 keV component of the electron neutrino, in the form of the recent observations of kinks in the beta-decay spectra of tritium, ¹⁴C, ³⁵S and ⁶³Ni. In this paper I show that most particle-physics models consistent with the 17 keV neutrino require a baryogenesis scale below 10⁶ GeV. Furthermore, models with a 17 keV neutrino typically contain new sources of CP violation, and the cosmological baryon asymmetry could be generated by anomalous electroweak interactions during a first-order weak phase transition.     

Flavour violation in supersymmetric theories

We investigate in detail the question of lepton-flavour violation in a SU(2) × U(1) supersymmetric model, where the breaking of supersymmetry (SUSY) is achieved through the coupling to N = 1 supergravity. It is shown that in the limit of degenerate neutrino masses, lepton flavour is exactly conserved. Allowing for neutrino masses compatible with present experimental limits, we analyse SUSY contributions to several lepton-flavour violating processes, comparing the size of these contributions with those already present in the standard Glashow-Salam-Weinberg model. In the case of μ → eγ, SUSY leads to a branching ratio two or three orders of magnitude larger than the corresponding branching ratio in the standard model, for gravitino and photino masses compatible with the experimental limits on the muon anomalous magnetic moment. In contrast, SUSY contributions to are always small, of the order of 10⁻² of the corresponding amplitudes in the standard model, if the gravitino and photino masses are constrained by the K_L − K_S mass difference.     

Unification of Poincaré, BRST and Parisi-Sourlas supersymmetries

Poincaré, BRST and Parisi-Sourlas supersymmetries are usually viewed as unrelated. Here we argue that they are in fact closely related. We argue that fermions in Poincaré SUSY theories can be interpreted as negative-dimensional phase space coordinates, in the Parisi-Sourlas sense. The Bose-Fermi balance then implies that the effective phase space dimensionality vanishes. We show that interacting Poincaré SUSY theories are related to the corresponding free theories by superrotations similar to BRST transformations. For superstrings we find that spacetime can be viewed as a zero-dimensional manifold in the sense of Parisi-Sourlas.     

Supersymmetric penguin contributions to the decay b\rightarrow s\gamma with non-universal squarks masses

We give explicit expressions for the amplitudes associated with the supersymmetric (SUSY) contributions to the process in the context of SUSY extensions of the standard model (SM) with non-universal soft SUSY breaking terms. From experimental data we deduce limits on the squark mass insertions obtained from different contributions (gluinos, neutralinos and charginos). Received: 20 April 2001 / Revised version: 14 December 2001 / Published online: 5 April 2002     

Supersymmetric unification at the millennium

We argue that the discovery of neutrino mass effects at super-Kamiokande implies a clear logical chain leading from the Standard Model, through the MSSM and the recently developed minimal left right supersymmetric models with a renormalizable see-saw mechanism for neutrino mass, to left right symmetric SUSY GUTS: in particular, SO(10) and SU(2) _L × SU(2) _R × SU(4) _C . The progress in constructing such GUTS explicitly is reviewed and their testability/falsifiability by lepton flavour violation and proton decay measurements emphasized. SUSY violations of the survival principle and the interplay between third generation Yukawa coupling unification and the structurally stable IR attractive features of the RG flow in SUSY GUTS are also discussed.     

From flavour to SUSY flavour models

If supersymmetry (SUSY) will be discovered, successful models of flavour not only have to provide an explanation of the flavour structure of the Standard Model fermions, but also of the flavour structure of their scalar superpartners. We discuss aspects of such “SUSY flavour” models, towards predicting both flavour structures, in the context of supergravity (SUGRA). We point out the importance of carefully taking into account SUSY-specific effects, such as 1-loop SUSY threshold corrections and canonical normalisation, when fitting the model to the data for fermion masses and mixings. This entangles the flavour model with the SUSY parameters and leads to interesting predictions for the sparticle spectrum. We demonstrate these effects by analyzing an example class of flavour models in the framework of an SU(5) Grand Unified Theory with a family symmetry with real triplet representations. For flavour violation through the SUSY soft breaking terms, the class of models realises a scheme we refer to as “Trilinear Dominance”, where flavour violation effects are dominantly induced by the trilinear terms.     

M-Theory Inspired Low Energy Phenomenology

In both the scalar quasi-massless SUSY breaking scenario and dilaton-dominant SUSY breaking scenario, we analyze experimental constraints to the parameter space in M theory compactified on S¹/Z₂. The sparticle spectrum and some phenomenological predictions are given.     

Hard and soft supersymmetry breaking for 'graphinos' in uniform magnetic fields

Using irreducible and reducible representations of the Dirac matrices, we study the two- and four-component quantum mechanical supersymmetric (SUSY) theories for ultrarelativistic fermions in .2 C 1/ dimensions ('graphinos') in a background uniform magnetic field perpendicular to their plane of motion. We then consider ordinary and parity-violating mass terms and identify the former as a soft SUSY breaking term and the latter as the hard SUSY breaking one.     

Painlevé IV coherent states

A simple way to find solutions of the Painlevé IV equation is by identifying Hamiltonian systems with third-order differential ladder operators. Some of these systems can be obtained by applying supersymmetric quantum mechanics (SUSY QM) to the harmonic oscillator. In this work, we will construct families of coherent states for such subset of SUSY partner Hamiltonians which are connected with the Painlevé IV equation. First, these coherent states are built up as eigenstates of the annihilation operator, then as displaced versions of the extremal states, both involving the related third-order ladder operators, and finally as extremal states which are also displaced but now using the so called linearized ladder operators. To each SUSY partner Hamiltonian corresponds two families of coherent states: one inside the infinite subspace associated with the isospectral part of the spectrum and another one in the finite subspace generated by the states created through the SUSY technique.     

Higher dimensional operator corrections to the goldstino Goldberger–Treiman vertices

The goldstino–matter interactions given by the Goldberger–Treiman relations can receive higher dimensional operator corrections of , where M denotes the mass of the mediators through which SUSY breaking is transmitted. These corrections in the gauge mediated SUSY breaking models arise from loop diagrams, and an explicit calculation of such corrections is presented. It is emphasized that the Goldberger–Treiman vertices are valid only below the mediator scale, and at higher energies goldstinos decouple from the MSSM fields. The implication of this fact for gravitino cosmology in GMSB models is mentioned. Received: 22 December 1998 / Revised version: 1 July 1999 / Published online: 17 February 2000     

Smuon in the NMSSM confronted with the muon g–2 anomaly and SUSY searches

Motivated by recent supersymmetry (SUSY) search results, which prefer most SUSY particles to be heavy, and the muon g–2 anomaly, which prefers colorless SUSY particles to be light, we explore the status of a light smuon (the SUSY partner of a left-handed muon lepton) in the next-to-minimal supersymmetric standard model (NMSSM). Assuming colored SUSY particles to be heavy, and considering numerous experimental constraints, including muon g-2, SUSY searches, and dark matter, we scan the parameter space in the NMSSM with \begin{document}$ \mathbb{Z}_3 $\end{document}-symmetry and check the status of colorless SUSY particles and their possible mass order, paying special attention to the smuon. After calculations and discussions, we find that the surviving samples can be divided into several scenarios, where the mass region and decay information of the smuon are given. Overall, the smuon mass can be approximately 0.1~1.8 TeV. These results may be useful for smuon searches at the LHC and future colliders.     

SUSY Confinement

In response to the present status that searching for SUSY particles has been unsuccessful, we propose a bold scenario that SUSY particles are confined inside hadrons with a required condition of P_R=1 in analog to the color confinement for quarks. The scenario seems to be able to reconcile the beautiful SUSY theory and non-observation at present experiments. On other aspects, some loopholes in the proposal emerge and require to be answered in the future research.     

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.