We propose a robust supergravity model of dynamical supersymmetry breaking and gauge mediation, and a natural embedding in non-perturbative string theory with D-branes. A chiral field (and its mirror) charged under "anomalous" U(1)'s acts as a Polonyi field whose hierarchical Polonyi-term can be generated by string instantons. Further quartic superpotential terms arise naturally as a tree-level decoupling effect of massive string states. A robust supersymmetry breaking minimum allows for gauge mediation with soft masses at the TeV scale, which we realise for a globally consistent SU(5) GUT model of Type I string theory, with a D1-instanton inducing the Polonyi term.
We present a simple four-dimensional model in which anomaly mediated supersymmetry breaking naturally dominates. The central ingredient is that the hidden sector is near a strongly-coupled infrared fixed-point for several decades of energy below the Planck scale. Strong renormalization effects then sequester the hidden sector from the visible sector. Supersymmetry is broken dynamically and requires no small input parameters. The model provides a natural and economical explanation of the hierarchy between the supersymmetry-breaking scale and the Planck scale, while allowing anomaly mediation to…
The general gauge mediation scenario provides a framework in which properties of a visible sector with soft supersymmetry breaking are computed from current correlation functions in the supersymmetry breaking hidden sector. In this paper we will use holography to model strongly coupled hidden sectors by weakly curved geometries and describe how the current correlators relevant for general gauge mediation are computed by holographic methods. We illustrate the general setup by a toy example which captures most of the relevant features.
We investigate SUSY breaking mediated through the deformation of the spacetime geometry due to the backreaction of a nontrivial configuration of a bulk scalar field. To illustrate its features, we work with a toy model in which the bulk is four dimensions. Using the superconformal formulation of SUGRA, we provide a systematic method of deriving the 3D effective action expressed by the superfields.
We provide string theory examples where a toy model of a SUSY GUT or the MSSM is embedded in a compactification along with a gauge sector which dynamically breaks supersymmetry. We argue that by changing microscopic details of the model (such as precise choices of flux), one can arrange for the dominant mediation mechanism transmitting SUSY breaking to the Standard Model to be either gravity mediation or gauge mediation. Systematic improvement of such examples may lead to top-down models incorporating a solution to the SUSY flavor problem.
These lectures give an introduction to the problem of finding a realistic and natural extension of the standard model based on spontaneously broken supersymmetry. Topics discussed at some length include the effective field theory paradigm, coupling constants as superfield spurions, gauge mediated supersymmetry breaking, and anomaly mediated supersymmetry breaking, including an extensive introduction to supergravity relevant for phenomenology.
We study gravity mediated supersymmetry breaking in four-dimensional effective theories derived from six-dimensional brane-world supergravity. Using the Noether method we construct a locally supersymmetric action for a bulk-brane system consisting of the minimal six-dimensional supergravity coupled to vector and chiral multiplets located at four-dimensional branes. Couplings of the bulk moduli to the brane are uniquely fixed, in particular, they are flavour universal. We compactify this system on T_2/Z_2 and derive the four-dimensional effective supergravity. The tree-level effective Kahler po…
I present a realistic model of dynamical supersymmetry breaking, in which a $U(1)_{B-L}$ gauge interaction communicates supersymmetry breaking to the standard fields. A distinctive superpartner spectrum is predicted in this model.
We discuss the possibility of finding scenarios, within type IIB string theory compactified on Calabi-Yau orientifolds with fluxes, for realizing gauge mediated supersymmetry breaking. We find that while in principle such scenarios are not ruled out, in practice it is hard to get acceptable constructions, since typically, supersymmetry breaking cannot be separated from the stabilization of the light modulus.
In this thesis we focus on the construction of models in which a supersymmetry breaking hidden sector is located on one fixed point of an extra dimensional interval and the effects are gauge mediated across this interval to the other fixed point where the supersymmetric standard model is located. We use the formalism of current correlators to encode supersymmetry breaking effects and explore flat, warped and deconstructed extra dimensions. We also apply these techniques to models of metastable supersymmetry breaking in N = 1 Supersymmetric Quantum Chromodynamics.
We consider the idea of combining the supersymmetry breaking and messenger sectors in models of gauge-mediated supersymmetry breaking. We discuss the advantages and problems of such models, and present an existence proof by constructing an explicit example. We explore in some detail the low-energy supersymmetry-breaking dynamics and the generation of supersymmetry-breaking soft masses of the standard model superpartners, and discuss many features which are likely to be shared by more realistic models with dynamical messengers.
The effects of heavy mass thresholds on anomaly-mediated soft supersymmetry breaking terms are discussed. While heavy thresholds completely decouple to lowest order in the supersymmetry breaking, it is argued that they do affect the breaking terms at higher orders. The relevant contributions typically occur at lower order in the loop expansion compared to purely anomaly mediated contributions. The non decoupling contributions may be used to render models in which the only source of supersymmetry breaking is anomaly mediation viable, by generating positive contributions to the sleptons' masses …
In this thesis, we study the details of some fundamental cosmological problems of the gauge mediated supersymmetry breakdown and we probe the supersymmetry breaking sector by cosmological arguments. We manifest that problems like the metastable vacuum selection and the gravitino overproduction in the reheated early universe are naturally absent in the most general class of gauge mediation models without including additional ingredients or assumptions. We also find that the gravitino can generically account for the bulk dark matter of the universe. Cosmological implications of a stringy UV-comp…
We use a new mechanism for generating a Fayet-Iliopoulos term in supergravity, which is not associated to an R symmetry, to construct a semi-realistic theory of slow-roll inflation for a theory with the same Kähler potential and superpotential as the KKLT string background (without anti-D3 branes). In our model, supersymmetry must be broken at a high scale in a hidden sector to ensure that the cutoff of the effective field theory is above the Hubble scale of inflation. The gravitino has a super-EeV mass and supersymmetry breaking is communicated to the observable sector through gravity mediati…
We show that supersymmetry breaking in a class of theories with SU(N) x SU(N-2) gauge symmetry can be studied in a calculable sigma model. We use the sigma model to show that the supersymmetry breaking vacuum in these theories leaves a large subgroup of flavor symmetries intact, and to calculate the masses of the low-lying states. By embedding the Standard Model gauge groups in the unbroken flavor symmetry group we construct a class of models in which supersymmetry breaking is communicated by both gravitational and gauge interactions. One distinguishing feature of these models is that the mess…
We describe local Calabi-Yau geometries with two isolated singularities at which systems of D3- and D7-branes are located, leading to chiral sectors corresponding to a semi-realistic visible sector and a hidden sector with dynamical supersymmetry breaking. We provide explicit models with a 3-family MSSM-like visible sector, and a hidden sector breaking supersymmetry at a meta-stable minimum. For singularities separated by a distance smaller than the string scale, this construction leads to a simple realization of gauge mediated supersymmetry breaking in string theory. The models are simple eno…
We investigate the communication of supersymmetry breaking to the Standard Model in theories of gauge mediated supersymmetry breaking with general weakly coupled messenger sectors. We calculate the one loop gaugino and two loop soft scalar masses for nonvanishing Str M^2 of the messenger sector. The soft scalar masses are sensitive to physics at scales higher than the messenger scale, in contrast to models with vanishing messenger supertrace. We discuss the implications of this ultraviolet sensitivity in theories with renormalizable and nonrenormalizable supersymmetry breaking sectors. We note…
We examine gauge and Yukawa coupling unification in models with gauge-mediated supersymmetry breaking. We work consistently to two-loop order, and include all weak, messenger and unification-scale threshold corrections. We find that successful unification requires unification-scale threshold corrections that are in conflict with the minimal SU(5) model, but are consistent with the modified missing doublet SU(5) model for small tan beta, and large tan beta with mu>0.
Theories with gauge-mediated supersymmetry breaking provide an interesting alternative to the scenario in which the soft terms of the low-energy fields are induced by gravity. These theories allow for a natural suppression of flavour violations in the supersymmetric sector and have very distinctive phenomenological features. Here we review their basic structure, their experimental implications, and the attempts to embed them into models in which all mass scales are dynamically generated from a single fundamental scale.
We suggest SU(5)$'$ in the hidden sector toward a possible gauge mediated supersymmetry breaking scenario for removing the SUSY flavor problem, with an example constructed in $\Z_{12-I}$ with three families. The example we present has the Pati-Salam type classification of particles in the observable sector and has no exotics at low energy. We point out that six or seven very light pairs of ${\bf 5}'$ and $\bar{\bf 5}'$ out of ten vectorlike $\five'$ and $\fiveb'$ pairs of SU(5)$'$ is achievable, leading to a possibility of an unstable supersymmetry breaking vacuum. The possibility of different…
New solutions in supersymmetry breaking through gravity mediation have been recently discovered. Such solutions have interesting properties regarding renormalisation and introduce new contributions in the scalar potential that may help to resolve some issues of the Standard Model. The purpose of this article is to investigate the consequences of these new structures. We construct a model related to these new solutions, the S2MSSM, and present some preliminary results on the effects of these new contributions, especially on the Standard Model's Higgs boson mass.
We study the U(1)_R-mediated supersymmetry breaking in a flux compactification of 6D chiral gauged supergravity with codimension-two branes. We consider a concrete model with manifest U(1)_R invariance for moduli stabilization and visible sector in the context of 4D effective supergravity with gauged U(1)_R and determine soft scalar masses in the visible sector mainly by a nonzero U(1)_R D-term. We obtain a low energy superparticle spectrum and discuss on the implications of the obtained non-universal scalar soft masses on the SUSY phenomenology such as dark matter relic abundances.
We propose a simple class of nonrenormalizable models of gauge mediated dynamical supersymmetry breaking. The models do not have gauge singlet fields. The Standard Model gauge group is embedded in the global symmetry of the SUSY breaking sector. At the renormalizable level the models possess a set of classical flat directions. Only one of those flat directions is unlifted by quantum effects, and requires nonrenormalizable term to stabilize the potential for the corresponding modulus. Large vacuum expectation value of this modulus at the minimum of the potential generates mass terms for the mes…
We analyze simple models of gauge mediated supersymmetry breaking in the context of supergravity. We distinguish two cases. One is when the messenger of the supersymmetry breaking is a non Abelian gauge force and the other is when the messenger is a pseudoanomalous U(1). We assume that these models originate from string theory and we impose the constraint of the vanishing of the cosmological constant requiring also the stabilization of the dilaton. In the first case, we do not find vacua that are consistent with the constraints of gauge mediation and have a zero tree level cosmological constan…
We propose a mechanism for mediating supersymmetry breaking in Type I string constructions. The basic set-up consists of a system of three D-branes: two parallel D-branes, a matter D-brane and a source D-brane, with supersymmetry breaking communicated via a third D-brane, the mediating D-brane, which intersects both of the parallel D-branes. We discuss an example in which the first and second family matter fields correspond to open strings living on the intersection of the matter D-brane and mediating D-brane, while the gauge fields, Higgs doublets and third family matter fields correspond to …
We study the transmission of supersymmetry breaking via gravitational interactions in a five-dimensional brane-world compactified on $S^1/Z_2$. We assume that chiral matter and gauge fields are confined at the orbifold fixed points, where supersymmetry is spontaneously broken by effective brane superpotentials. Using an off-shell supergravity multiplet we integrate out the auxiliary fields and examine the couplings between the bulk supergravity fields and boundary matter fields. The corresponding tree-level shift in the bulk gravitino mass spectrum induces one-loop radiative masses for the bou…
Minimal Supersymmetric Standard Model with gauge mediated supersymmetry breaking has all the necessary ingredients for a successful sub-eV Hubble scale inflation $H_{\rm inf} \sim 10^{-3}-10^{-1}$ eV. The model generates the right amplitude for scalar density perturbations and a spectral tilt within the range, $0.90 \leq n_s \leq 1$. The reheat temperature is $T_{\rm R} \ls 10$ TeV, which strongly prefers electroweak baryogenesis and creates the right abundance of gravitinos with a mass $m_{3/2} \gs 100$ keV to be the dark matter.
We introduce new mechanisms for the communication of supersymmetry breaking via gauge interactions. These models do not require complicated dynamics to induce a nonvanishing F term for a singlet. The first class of models communicates supersymmetry breaking to the visible sector through a ``mediator" field that transforms under both a messenger gauge group of the dynamical supersymmetry breaking sector and the standard model gauge group. This model has distinctive phenomenology; in particular, the scalar superpartners should be heavier by at least an order of magnitude than the gaugino superpa…
We consider a class of models in which supersymmetry breaking is communicated dominantly via a U'(1) gauge interaction, which also helps solve the μproblem. Such models can emerge naturally in top-down constructions and are a version of split supersymmetry. The spectrum contains heavy sfermions, Higgsinos, exotics, and Z' ~ 10-100 TeV; light gauginos ~ 100-1000 GeV; a light Higgs ~ 140 GeV; and a light singlino. A specific set of U'(1) charges and exotics is analyzed, and we present five benchmark models. Implications for the gluino lifetime, cold dark matter, and the gravitino and neutrino ma…
In Grand Unified Theories (GUTs) from orbifold and various string constructions the generic vector-like particles do not need to form complete SU(5) or SO(10) representations. To realize them concretely, we present orbifold SU(5) models, orbifold SO(10) models where the gauge symmetry can be broken down to flipped SU(5) X U(1)_X or Pati-Salam SU(4)_C X SU(2)_L X SU(2)_R gauge symmetries, and F-theory SU(5) models. Interestingly, these vector-like particles can be at the TeV-scale so that the lightest CP-even Higgs boson mass can be lifted, or play the messenger fields in the Gauge Mediated Sup…
We provide a simple solution to the $μ/B_μ$ problem in the gauge-mediated Next-to-Minimal Supersymmetric Standard Model. In this model the messenger sector contains one pair of $3+\bar 3$ and one pair of $2+\bar 2$ messengers. These two messenger pairs couple to different gauge singlets in the hidden sector in which supersymmetry (SUSY) is broken. Such a gauge-mediation structure can naturally arise in many backgrounds. Because of the two effective SUSY breaking scales $\frac{< F_i>}{< M_i>}$ in the messenger sector, the renormalization group evolutions of the soft SUSY breaking parameters can…
We analyze in detail a specific 5-dimensional realization of a "brane-universe" scenario where the visible and hidden sectors are localized on spatially separated 3-branes coupled only by supergravity, with supersymmetry breaking originating in the hidden sector. Although general power counting allows order 1/M_{Planck}^2 contact terms between the two sectors in the 4-dimensional theory from exchange of supergravity Kaluza-Klein modes, we show that they are not present by carefully matching to the 5-dimensional theory. We also find that the radius modulus corresponding to the size of the compa…
We present a complete, viable model of gravity-mediated supersymmetry breaking that is safe from all flavor constraints. The central new idea is to employ a supersymmetry breaking sector without singlets, but with D-terms comparable to F-terms, causing supersymmetry breaking to be dominantly communicated through U(1)_R-symmetric operators. We construct a visible sector that is an extension of the MSSM where an \emph{accidental} U(1)_R symmetry emerges naturally. Gauginos acquire Dirac masses from gravity-mediated D-terms, and tiny Majorana masses from anomaly-mediated contributions. Contributi…
This paper investigates the parameter space of theories with gauge mediated supersymmetry breaking leading to gravitino (cold) dark matter with mass m_{3/2}= 1keV - 10MeV. We pay particular attention to the cosmological role of messenger fields. Cosmology requires that these messengers decay to the visible sector if the lightest messenger mass M_X > 30TeV. We then examine the various possible messenger number violating interactions allowed by the symmetries of the theory and by phenomenology. Late messenger decay generally results in entropy production hence in the dilution of pre-existing gra…
It is shown that gravitinos with mass m_{3/2} ~ 0.1-1 MeV may provide suitable cold dark matter candidates in scenarios of gauge mediated supersymmetry breaking (GMSB) under SO(10) grand unification coupled to supergravity, which accommodate a messenger sector of mass scale M_X ~ 10^6 GeV. This is due to the combined effects of renormalizable loop-suppressed operators and generic non-renormalizable ones governing the dilution of a pre-existing equilibrium gravitino abundance via messenger decay. The above range of gravitino and messenger masses can be accommodated in indirect GMSB scenarios. T…
