Pattern Of Supersymmetry Breaking Research Articles

A hamiltonian lattice study of the two-dimensional Wess-Zumino model

We investigate a Hamiltonian lattice version of the two-dimensional Wess-Zumino model by Quantum Monte Carlo simulations. In order to study the pattern of supersymmetry breaking, we measure the ground state energy and the correlation length along a trajectory approaching the continuum limit. The algorithm is very effective in measuring the ground state energy, and adequate for the correlation length.

Additional stringy sources for electric dipole moments.

We show that string models with low energy supersymmetry which accommodate the fermion mass hierarchy generally give nonuniversal soft trilinear couplings (A terms). In conjunction with the apparently large Cabibbo-Kobayashi-Maskawa (CKM) phase, this results in large fermion electric dipole moments (EDMs) even in the absence of CP violating phases in the supersymmetry breaking auxiliary fields and the micro term. Nonobservation of the EDMs therefore implies that strings select special flavor and/or supersymmetry breaking patterns.

Hamiltonian Monte Carlo simulation of the two-dimensional Wess-Zumino model

We study a Hamiltonian lattice version of the two-dimensional Wess-Zumino model. Preliminary results obtained by Quantum Monte Carlo with a many-parameter guiding wave function are presented. We analyze the pattern of supersymmetry breaking by measuring the ground state energy and a set of supersymmetric Ward identities. The algorithm is quite effective and allows very precise measurements.

On SUSY breaking and χSB from string duals

We find regular string duals of three-dimensional N=1 SYM with a Chern–Simons interaction at level k for SO and Sp gauge groups. Using the string dual we exactly reproduce the conjectured pattern of supersymmetry breaking proposed by Witten by showing that there is dynamical supersymmetry breaking for k< h/2 while supersymmetry remains unbroken for k⩾ h/2, where h is the dual Coxeter number of the gauge group. We also find regular string duals of four-dimensional N=1 SYM for SO and Sp gauge groups and exactly reproduce the expected pattern of chiral symmetry breaking Z 2 h → Z 2 by analyzing the symmetries of the string solution.

D-branes as solitons of anN=1,D=10noncommutative gauge theory

We consider a Dp brane within a D9 brane in the presence of a B-field whose polarization is {\em transverse} to the Dp brane. To be definite, we take a D3-D9 system. It is observed that the system has the same pattern of supersymmetry breaking as that of a soliton of the six dimensional non-commutative gauge theory that is obtained by dimensional reduction of an {\cal N}=1, D=10 gauge theory. These results indicate that the soliton solution is the low energy realization of a D3 brane in a D9 brane with a transverse B-field, hence can be viewed as a generalization of the previous results in the literature where similar observations were made for lower codimensional cases.

Extended superconformal symmetry and Calogero-Marchioro model

We show that the two dimensional Calogero-Marchioro Model (CMM) without the harmonic confinement can naturally be embedded into an extended SU(1,1|2) superconformal Hamiltonian. We study the quantum evolution of the superconformal Hamiltonian in terms of suitable compact operators of the N=2 extended de Sitter superalgebra with central charge and discuss the pattern of supersymmetry breaking. We also study the arbitrary D dimensional CMM having dynamical OSp(2|2) supersymmetry and point out the relevance of this model in the context of the low energy effective action of the dimensionally reduced Yang-Mills theory.

Microscopic spectrum of the QCD Dirac operator in three dimensions

The microscopic spectral correlators of the Dirac operator in three-dimensional Yang–Mills theory coupled to fundamental fermions and with three or more colours are derived from the supersymmetric formulation of partially quenched effective Lagrangians. The flavour supersymmetry breaking patterns are appropriately identified and used to calculate the corresponding finite volume partition functions from Itzykson–Zuber type integrals over supersymmetric cosets. New and simple determinant expressions for the spectral correlators in the mesoscopic scaling region are thereby found. The microscopic spectrum derived from the effective finite volume partition function of three-dimensional QCD agrees with earlier results based on the unitary ensemble of random matrix theory and extends the corresponding calculations for QCD in four dimensions.

Neutrino mixing and flavour changing processes

We study the implications of a large ν μ – ν τ mixing angle on flavour changing transitions of quarks and leptons in supersymmetric extensions of the standard model. Two patterns of supersymmetry breaking are considered, models with modular invariance and the standard scenario of universal soft breaking terms at the GUT scale. The analysis is performed for two symmetry groups G⊗ U(1) F , with G= SU(5) and G= SU(3) 3, where U(1) F is a family symmetry. Models with modular invariance are in agreement with observations only for restricted scalar quark and gaugino masses, M ̄ q 2/m g ̃ 2≃7/9 and m b ̃ >350 GeV. A characteristic feature of models with large tan β and radiatively induced flavour mixing is a large branching ratio for μ→ eγ. For both symmetry groups and for the considered range of supersymmetry breaking mass parameters we find BR( μ→ eγ)>10 −14.

Neutrino mixing and the pattern of supersymmetry breaking

We study the implications of a large νμ–ντ mixing angle on lepton flavour violating radiative transitions in supersymmetric extensions of the standard model. The transition rates are calculated to leading order in ϵ, the parameter which characterizes the flavour mixing. The uncertainty of the predicted rates is discussed in detail. For models with modular invariance the branching ratio BR(μ→eγ) mostly exceeds the experimental upper limit. In models with radiatively induced flavour mixing the predicted range includes the upper limit, if the Yukawa couplings in the lepton sector are large, as favoured by Yukawa coupling unification.

Charge and colour breaking constraints in the MSSM with non-universal SUSY breaking

We examine charge/colour breaking along directions in supersymmetric field space which are F and D-flat. We catalogue the dangerous directions and include some new ones which have not previously been considered. Analytic expressions for the resulting constraints are provided which are valid for all patterns of supersymmetry breaking. As an example we consider a recently proposed pattern of supersymmetry breaking derived in Horava-Witten M-theory, and show that there is no choice of parameters for which the physical vacuum is a global minimum.

A REVIEW OF THREE-FAMILY GRAND UNIFIED STRING MODELS

We review the construction and classification of three-family grand unified models within the framework of asymmetric orbifolds in perturbative heterotic superstring. We give a detailed survey of all such models which is organized to aid analysis of their phenomenological properties. We compute tree level superpotentials for these models. These superpotentials are used to analyze the issues of proton stability (doublet–triplet splitting and R-parity-violating terms) and Yukawa mass matrices. To have agreement with phenomenological data all these models seem to require a certain degree of fine-tuning. We also analyze the possible patterns of supersymmetry breaking in these models. We find that the supersymmetry breaking scale comes out either too high to explain the electroweak hierarchy problem, or below the electroweak scale unless some degree of fine-tuning is involved. Thus, none of the models at hand seem to be phenomenologically flawless.

Anomalous D-term, dynamical supersymmetry breaking and dynamical gauge couplings

We analyze the structure of the vacuum and supersymmetry breaking pattern in Fayet-Iliopoulos models with dynamical gauge coupling and Planck-scale value of the FI parameter. We show that in this class of models supersymmetry is generically broken, but the mere presence of the D-term is not sufficient to stop the running away of the modulus responsible for the value of the gauge coupling — the dilaton. To stabilize the dilaton, one has to include an additional dilaton-dependent part in the superpotential. The presence of a large D-term gives rise to the mixed dilaton/ D-term dominated scenarios of susy breaking, which allow horizontal hierarchy generation. Models that can serve as secluded sectors in gauge mediation scenarios are discussed. It is shown that when when the FI parameter and the gauge coupling are dynamical variables, the D-term dominated Universe does not allow for an inflationary period.

Non-linear realizations of SU (2) × U (1) in the MSSM. Model independent analysis and g−2 of W bosons

We perform a model-independent analysis of the spontaneously broken phase of an SU (2) × U (1) supersymmetric gauge theory, by using a non-linear parametrization of the Goldstone sector of the theory. The non-linear variables correspond to an SL(2, C ) superfield matrix in terms of which a non-linear lagrangian can be constructed, and the pattern of supersymmetry breaking investigated. The supersymmetric order parameter is the VEV of the neutral pseudo-Goldstone boson. Some applications of this technique are considered, in relation to the minimal supersymmetric standard model, and to determine the g−2 of the W-bosons in the limit of large top mass.

Fractionally charged particles and supersymmetry breaking in 4D strings

Four-dimensional string theories predict in general the existence of light exotic particles with fractional electric charges. Such particles could escape present observations if they are confined by a gauge group of the “hidden” sector into integrally charged states. It is conceivable that the same gauge group is also responsible for dynamical supersymmetry breaking, via gaugino and scalar condensation. The communication of the breaking to the observable sector is not mediated by ordinary gauge interactions, implying that the confining scale can be in the TeV region. We study the main phenomenological implications of this possibility. In particular, we analyze the pattern of supersymmetry breaking and the mass-spectrum of the particles. We also show that this scenario can be consistent with the unification of all coupling constants at the string scale.

Anomalous magnetic moment of the muon and neutral-current constraints in a supersymmetric SU(2)L x U(1)I3R x U(1)B-L model inspired by superstring theories.

An extension of the standard supersymmetric model, SU(2${)}_{\mathit{L}}$\ifmmode\times\else\texttimes\fi{}\ifmmode\times\else\texttimes\fi{}U(1${)}_{{\mathit{I}}_{3}\mathit{R}}$\ifmmode\times\else\texttimes\fi{}U(1${)}_{\mathit{B}\mathrm{\ensuremath{-}}\mathit{L}}$, motivated by superstrings and baryon-number conservation is analyzed. A possible pattern of supersymmetry breaking from ${\mathrm{E}}_{6}$ and the phenomenological implications for such a model are studied. In particular it is found that the neutral currents restrict ${M}_{Z\mathcal{'}}$\ensuremath{\ge}240 GeV. Constraints on the g-2 factor of the muon are also examined.

The low-energy effective field theory from four-dimensional superstrings

We derive the low-energy effective supergravity field theory obtained from a fermionic formulation of four-dimensional superstrings. It contains a single dilaton supermultiplet parametrizing an SU(1, 1)/U(1) manifold, three self-conjugate sets of matter supermultiplets parametrizing SO( m, 2)/SO( m)×SO(2) manifolds, and chiral matter supermultiplets parametrizing a product of SU( M, 1)/SU( M)×U(1) manifolds. We derive the Yukawa couplings of the theory and identify some of the self-conjugate matter fields as Higgses. We also discuss the possible pattern of supersymmetry breaking.

Physical state conditions and supersymmetry breaking in quantum mechanics

It is shown, by giving an explicit example, how the conditions imposed on physically admissible states can affect the pattern of supersymmetry breaking and, as a consequence, the values of physically interesting quantities such as the Witten index. As a by-product an unusual kind of explicit supersymmetry breaking is observed, where the supersymmetry algebra still holds formally, as well as a spontaneous breakdown of supersymmetry, which is not induced by instantons.

The dynamics of supersymmetric sigma models with central charges

The O( n + 1) and O( n, 1) supersymmetric σ-models with central charges are constructed explicitly. Patterns of supersymmetry breaking are classified in the tree approximation and in the large- n limit, where a great deal of interesting structure is found. In the case of the non-compact O( n,1) models it is found that inclusion of central charges leads to theories free of infrared divergence.

Hamiltonian Monte Carlo study of (1+1)-dimensional models with restricted supersymmetry on the lattice

Lattice versions with restricted supersymmetry of simple (1+1)-dimensional supersymmetric models are numerically studied using a local hamiltonian Monte Carlo method. The pattern of supersymmetry breaking closely follows the expectations of Bartels and Bronzan obtained in an alternative lattice formulation.

Supersymmetric QCD and its massless limit: An effective lagrangian analysis

Supersymmetric QCD is studied by an effective lagrangian method. When all flavours are massive supersymmetric vacua, reproducing the known value of Witten's index, do exist and decoupling of heavy flavours occurs When one or more flavours become massless, some chirality breaking order parameters run to infinity suggesting a non-smooth zero mass limit, in contrast with the case of ordinary QCD. Possible implications of these results on chiral and/or supersymmetry breaking patterns in the massless theory are briefly discussed.