Gauge-mediated Models Research Articles

Dynamical supersymmetry breaking, with flavor

We explore calculable models with low-energy supersymmetry where the flavor hierarchy is generated by quark and lepton compositeness, and where the composites emerge from the same sector that dynamically breaks supersymmetry. The observed pattern of Standard Model fermion masses and mixings is obtained by identifying the various generations with composites of different dimension in the ultraviolet. These "single-sector" supersymmetry breaking models give rise to various spectra of soft masses which are, in many cases, quite distinct from what is commonly found in models of gauge or gravity mediation. In typical models which satisfy all flavor-changing neutral current constraints, both the first and second generation sparticles have masses of order 20 TeV, while the stop mass is near 1 TeV. In other cases, all sparticles obtain masses of order 1 TeV predominantly from gauge mediation, even though the first two generations are composite.

Low-scale gauge mediation and composite messenger dark matter

In recent works, we have proposed a possible dark matter in composite messenger gauge mediation models. In this paper, we discuss the details of a composite messenger model taking a possible supersymmetry breaking scenario and show that the correct dark matter abundance and a successful gauge mediation can be realized.

Phenomenological aspects of gauge mediation with sequestered supersymmetry breaking in light of dark matter detection

In a recent work, a model of gauge mediation with sequestered supersymmetry (SUSY) breaking was proposed. In this model, the mass of the gravitino is O(100) GeV without causing the flavor-changing neutral-current problem. In contrast to traditional gauge mediation, the gravitino is not the lightest SUSY particle and the neutralino is the candidate of the dark matter. In this paper, we investigate phenomenological aspects of this model and discuss the possibility of the direct detection of the dark matter. In particular, we focus on the light neutralino case and find that the light-Higgsino scenario such as the focus point is interesting, taking account of the recent CDMS result.

On uplifted SUSY-breaking vacua and direct mediation in generalized SQCD

We search for viable models of direct gauge mediation, where the SUSY-breaking sector is (generalized) SQCD, which has cosmologically favorable uplifted vacua even when the reheating temperature is well above the messenger scale. This requires a relatively large tadpole term in the scalar potential for the spurion field X and, consequently, we argue that pure (deformed) SQCD is not a viable model. On the other hand, in SQCD with an adjoint, which is natural e.g. in string theory, assuming an appropriate sign in the Kahler potential for X, such metastable vacua are possible.

Patterns of soft masses from general semi-direct gauge mediation

We give a general formulation of semi-direct gauge mediation of supersymmetry breaking where the messengers interact with the hidden sector only through a weakly gauged group. Using this general formulation, we provide an explicit proof that the MSSM gaugino masses are vanishing to leading order in the gauge couplings. On the other hand, the MSSM sfermion masses have, generically, a non-vanishing leading contribution. We discuss how such a mechanism can successfully be combined with other mediation schemes which give tachyonic sfermions, such as sequestered anomaly mediation and some direct gauge mediation models.

Low scale direct gauge mediation with perturbatively stable vacuum

In a class of direct gauge mediation with a perturbatively stable SUSY breaking vacuum, gaugino masses vanish at the leading order of SUSY breaking F-term. We study the allowed parameter space of the gauge mediation models. By imposing a Tevatron bound on the lightest chargino mass \( {m_{\tilde \chi_1^\pm }} \gtrsim 270\;{\text{eV}} \) and a warm dark-matter mass bound on the light gravitino mass m 3/2 ≲ 16 eV, we find that almost all the parameter space is excluded. Near future experiments may completely exclude, or possibly discover, the scenario.

Relaxing a constraint on the number of messengers in a low-scale gauge mediation

We propose a mechanism for relaxing a constraint on the number of messengers in low-scale gauge mediation models. The Landau pole problem for the standard-model gauge coupling constants in the low-scale gauge mediation can be circumvented by using our mechanism. An essential ingredient is a large positive anomalous dimension of messenger fields given by a large Yukawa coupling in a conformal field theory at high energies. The positive anomalous dimension reduces the contribution of the messengers to the beta function of the standard-model gauge couplings.

Studying Gaugino Mass in Semi-Direct Gauge Mediation

We study gaugino mass generation in the context of semi-direct gauge mediation models, where the messengers are charged under both the hidden sector and the standard model gauge groups while they do not play important roles in dynamical supersymmetry breaking. We clarify the cancellation of the leading contributions of the supersymmetry breaking effects to the gaugino mass in this class of models in terms of the macroscopic effective theory of the hidden sector dynamics. We also consider how to retrofit the model so that we obtain the non-vanishing leading contribution to the gaugino mass.

Erratum: Natural semidirect gauge mediation and D-branes at singularities [Phys. Rev. D80, 045001 (2009)

We consider semi-direct gauge mediation models of supersymmetry breaking where the messengers are composite fields and their supersymmetric mass is naturally generated through quartic superpotential couplings. We show that such composite messenger models can be easily embedded in quiver gauge theories arising from D-branes at Calabi-Yau singularities, and argue that semi-direct gauge mediation is in fact a very natural option for supersymmetry breaking in D-brane models. We provide several explicit examples and discuss their salient phenomenological properties.

Axions in gauge mediation

In supersymmetric theories, the presence of axions usually implies the existence of a non-compact, (pseudo)moduli space. In gauge mediated models, the axion would seem a particularly promising dark matter candidate. The cosmology of the moduli then constrains the gravitino mass and the axion decay constant; the former can't be much below 10 MeV; the latter can't be much larger than 10^{13} GeV. Axinos, when identifiable, are typically heavy and do not play an important role in cosmology.

Reheating temperature and gauge mediation models of supersymmetry breaking

For supersymmetric theories with gravitino dark matter, the maximal reheating temperature consistent with big bang nucleosynthesis bounds arises when the physical gaugino masses are degenerate. We consider the cases of a stau or sneutrino next-to-lightest superpartner, which have relatively less constraint from big bang nucleosynthesis. The resulting parameter space is consistent with leptogenesis requirements, and can be reached in generalized gauge mediation models. Such models illustrate a class of theories that overcome the well-known tension between big bang nucleosynthesis and leptogenesis.

Phenomenology of pure general gauge mediation

We investigate the phenomenology of general gauge mediation in the MSSM. We apply the strict definition of gauge mediated SUSY-breaking where B_mu is generated only through gauge interactions, and as a result is very close to zero at the messenger scale. In this setup tan beta is a prediction rather than an input. The input parameters are independent scales for the gaugino masses, the scalar masses and the messenger mass in accord with general gauge mediation. We investigate the spectra, the constraints on the parameter space from direct searches and indirect observables, as well as fine-tuning. The favoured region of parameter space includes and interpolates between non-split and mildly split SUSY, characteristic of ordinary gauge mediation and direct gauge mediation models, respectively.

Gravitino dark matter fromQ-ball decays

Affleck-Dine baryogenesis, accompanied by the formation and subsequent decay of $Q$-balls, can generate both the baryon asymmetry of the Universe and dark matter in the form of gravitinos. The gravitinos from $Q$-ball decay dominate over the thermally produced population if the reheat temperature ${T}_{R}\ensuremath{\lesssim}{10}^{7}\text{ }\text{ }\mathrm{GeV}$. We show that a gravitino with mass $\ensuremath{\sim}1\text{ }\text{ }\mathrm{GeV}$ is consistent with all observational bounds and can explain the baryon-to-dark-matter ratio in the gauge-mediated models of supersymmetry breaking for a wide range of cosmological and $Q$-ball parameters. Moreover, decaying $Q$-balls can be the dominant production mechanism for ${m}_{3/2}<1\text{ }\text{ }\mathrm{GeV}$ gravitinos if the $Q$-balls are formed from a $(B\ensuremath{-}L)=0$ condensate, which produces no net baryon asymmetry. Gravitinos with masses in the range $50\text{ }\text{ }\mathrm{eV}\ensuremath{\lesssim}{m}_{3/2}\ensuremath{\lesssim}100\text{ }\text{ }\mathrm{keV}$ produced in this way can act as warm dark matter and can have observable imprint on the small-scale structure.

The footprint of F-theory at the LHC

Recent work has shown that compactifications of F-theory provide a potentially attractive phenomenological scenario. The low energy characteristics of F-theory GUTs consist of a deformation away from a minimal gauge mediation scenario with a high messenger scale. The soft scalar masses of the theory are all shifted by a stringy effect which survives to low energies. This effect can range from 0 GeV up to ~ 500 GeV. In this paper we study potential collider signatures of F-theory GUTs, focussing in particular on ways to distinguish this class of models from other theories with an MSSM spectrum. To accomplish this, we have adapted the general footprint method developed recently for distinguishing broad classes of string vacua to the specific case of F-theory GUTs. We show that with only 5 fb^(-1) of simulated LHC data, it is possible to distinguish many mSUGRA models and low messenger scale gauge mediation models from F-theory GUTs. Moreover, we find that at 5 fb^(-1), the stringy deformation away from minimal gauge mediation produces observable consequences which can also be detected to a level of order ~ +/- 80 GeV. In this way, it is possible to distinguish between models with a large and small stringy deformation. At 50 fb^(-1), this improves to ~ +/- 10 GeV.

Building a better minimal supergravity: WIMP dark matter without flavor violation

The appearance of a natural dark matter candidate, the neutralino, is among the principal successes of minimal supergravity (mSUGRA) and its descendents. In lieu of a suitable ultraviolet completion, however, theories of gravity-mediated supersymmetry breaking such as mSUGRA suffer from arbitrary degrees of flavor violation. Though theories of gauge-mediated supersymmetry breaking are free from such prohibitive flavor violation, they typically lack natural neutralino dark matter candidates. Yet this conventional dichotomy breaks down when the hidden sector is strongly coupled; in models of gauge-mediated supersymmetry breaking, the neutralino may be the lightest supersymmetric particle if the fields of the hidden sector possess large anomalous dimensions. In fact, general models of so-called ``sequestered'' gauge mediation possess the full richness of neutralino dark matter found in mSUGRA without corresponding flavor problems. Here we explore generalized models of sequestered gauge mediation and the rich variety of neutralino dark matter they exhibit.

Affleck-Dine dynamics,Q-ball formation, and thermalization

We present both analytically and numerically a consistent analysis of the dynamics from the Affleck-Dine (AD) mechanism to the subsequent semiclassical evolution in both gravity-mediated and gauge-mediated models. We obtain analytically the elliptic motions in the AD dynamics as the analogy of the well-known Kepler-problem, and by solving the equations of motion on a lattice, we find that the semiclassical evolution goes through three distinct stages as a nonequilibrium process of reheating the Universe: prethermalization, bubble collisions and thermalization. We report that the second stage of our case lasts rather long compared to the second stage of the reheating case, and the thermalization process is unique due to the presence of ``thermal $Q$-balls''.

Non-thermal gravitino dark matter in gauge mediation

We show that gravitinos produced by decays of a supersymmetry breaking scalar field (the pseudo-moduli field) can naturally explain the observed abundance of dark matter in a certain class of the gauge mediation models. We study the decay processes as well as cosmological constraints on this scenario in detail, particularly focusing on different behavior of the real and imaginary components of the pseudo-moduli field. Cosmologically viable scenario emerges when the gravitino and the pseudo-moduli masses are O(10-100) MeV and O(100) GeV, respectively.

F-theory, GUTs, and the weak scale

In this paper we study a deformation of gauge mediated supersymmetry breaking in a class of local F-theory GUT models where the scale of supersymmetry breaking determines the value of the mu term. Geometrically correlating these two scales constrains the soft SUSY breaking parameters of the MSSM. In this scenario, the hidden SUSY breaking sector involves an anomalous U(1) Peccei-Quinn symmetry which forbids bare mu and B mu terms. This sector typically breaks supersymmetry at the desired range of energy scales through a simple stringy hybrid of a Fayet and Polonyi model. A variant of the Giudice-Masiero mechanism generates the value mu ~ 10^2 - 10^3 GeV when the hidden sector scale of supersymmetry breaking is F^(1/2) ~ 10^(8.5) GeV. Further, the B mu problem is solved due to the mild hierarchy between the GUT scale and Planck scale. These models relate SUSY breaking with the QCD axion, and solve the strong CP problem through an axion with decay constant f_a ~ M_(GUT) * mu / L, where L ~ 10^5 GeV is the characteristic scale of gaugino mass unification in gauge mediated models, and the ratio \mu / L ~ M_(GUT)/M_(pl) ~ 10^(-3). We find f_a ~ 10^12 GeV, which is near the high end of the phenomenologically viable window. Here, the axino is the goldstino mode which is eaten by the gravitino. The gravitino is the LSP with a mass of about 10^1 - 10^2 MeV, and a bino-like neutralino is (typically) the NLSP with mass of about 10^2 - 10^3 GeV. Compatibility with electroweak symmetry breaking also determines the value of tan(beta) ~ 30 +/- 7.

Pseudomoduli dark matter

We point out that pseudomoduli — tree-level flat directions that often accompany dynamical supersymmetry breaking — can be natural candidates for TeV-scale dark matter in models of gauge mediation. The idea is general and can be applied to different dark matter scenarios, including (but not limited to) those of potential relevance to recent cosmic ray anomalies. We describe the requirements for a viable model of pseudomoduli dark matter, and we analyze two example models to illustrate the general mechanism — one where the pseudomoduli carry Higgsino-like quantum numbers, and another where they are SM singlets but are charged under a hidden-sector U(1)' gauge group.

Conversion of baryonic fermions into squarks in neutron stars from supersymmetric dark matterQ-balls

The gauge-mediated model of supersymmetry breaking implies that stable nontopological solitons, $Q$-balls, could form in the early Universe and comprise the dark matter. It is shown that the inclusion of the effects from gravity-mediation set an upper limit on the size of $Q$-balls. When in a dense baryonic environment $Q$-balls grow until reaching this limiting size at which point they fragment into two equal-sized $Q$-balls. This $Q$-splitting process will rapidly destroy a neutron star that absorbs even one $Q$-ball. The new limits on $Q$-ball dark matter require an ultralight gravitino ${m}_{3/2}\ensuremath{\lesssim}\mathrm{keV}$, naturally avoiding the gravitino overclosure problem, and providing the minimal supersymmetric standard model with a dark matter candidate where gravitino dark matter is not viable.