Gaugino Mediation Research Articles

Axion induced SUSY breaking and focus point gaugino mediation

We consider a scenario where supersymmetry breaking, its mediation, and the cancellation of the theta parameter of SU(3)C are all caused by a single chiral multiplet. The string axion multiplet is a natural candidate of such a superfield. We show that the scenario provides a convincing basis of focus point gaugino mediation, where the electroweak scale is explained with a moderate tuning among the parameters of the theory.

Gaugino mediation scenarios for muon g \u2212 2 and dark matter

We explore the possibility that the muon g − 2 anomaly and the nature of dark matter can be simultaneously explained within the framework of gaugino mediation, focusing on bino-like dark matter where the observed abundance is obtained via co-annihilations. The minimal model with non-universal gaugino masses is excluded by stau vacuum instability, although this constraint can be somewhat relaxed via the addition of a universal soft scalar mass (or B − L gaugino mediation). A more promising alternative is gaugino+Higgs mediation, which significantly raises the soft masses of the third generation sfermions leading to a split spectrum. In this framework, the muon g − 2 can be easily explained and the dark matter abundance obtained through either bino-wino or bino-slepton co-annihilations.

Implications of the 750 GeV diphoton excess in gaugino mediation

The 750 GeV diphoton excess reported by ATLAS and CMS indicates the presence of several pairs of the vector-like matter multiplets around TeV scale. If that is the case, radiative corrections from the $SU(3)$ gauge interaction significantly change from those of MSSM, and the infrared-free nature of the gauge interaction leads to characteristic SUSY mass spectra: a ratio of a squark mass to the gluino mass, and scalar trilinear couplings are enhanced at the low-energy scale. Consequently, even in gaugino mediation models, the Higgs boson mass of 125 GeV is explained with the fairly light gluino of 2-3 TeV, which can be accessible at the LHC.

Summary of the searches for squarks and gluinos using s = 8 $$ \sqrt{s}=8 $$ TeV pp collisions with the ATLAS experiment at the LHC

A summary is presented of ATLAS searches for gluinos and first- and second-generation squarks in final states containing jets and missing transverse momentum, with or without leptons or b-jets, in the $\sqrt{s}$ = 8 TeV data set collected at the Large Hadron Collider in 2012. This paper reports the results of new interpretations and statistical combinations of previously published analyses, as well as a new analysis. Since no significant excess of events over the Standard Model expectation is observed, the data are used to set limits in a variety of models. In all the considered simplified models that assume R-parity conservation, the limit on the gluino mass exceeds 1150 GeV at 95% confidence level, for an LSP mass smaller than 100 GeV. Furthermore, exclusion limits are set for left-handed squarks in a phenomenological MSSM model, a minimal Supergravity/Constrained MSSM model, R-parity-violation scenarios, a minimal gauge-mediated supersymmetry breaking model, a natural gauge mediation model, a non-universal Higgs mass model with gaugino mediation and a minimal model of universal extra dimensions.

Higgs boson mass of 125 GeV andg−2of the muon in a gaugino mediation model

Gaugino mediation is very attractive since it is free from the serious flavor problem in the supersymmetric standard model. We show that the observed Higgs boson mass at around 125 GeV and the anomaly of the muon g-2 can be easily explained in gaugino mediation models. It should be noted that no dangerous CP violating phases are generated in our framework. Furthermore, there are large parameter regions which can be tested not only at the planned International Linear Collider but also at the coming 13-14 TeV Large Hadron Collider.

Upper bounds on gluino, squark and higgisino masses in the focus point gaugino mediation with a mild fine tuning Δ ≤ 100

We show that upper bounds on the masses for gluino, squarks and higgsino are $m_{gluino} \le 5.5$ TeV, $m_{squark} \le 4.7$ TeV and $m_{higgsino} \le 650$ GeV in a focus point gaugino mediation. Here, we impose a mild fine tuning $\Delta \le 100$. This result shows that it is very challenging for the LHC to exclude the focus point gaugino mediation with the mild fine tuning. However, the ILC may have a potential for excluding the focus point gaugino mediation with such a mild fine tuning. It is also shown that vector-like matters reduce the required masses of the squark (stop) and gluino to explain the observed Higgs boson mass and enhance the testability of the model at the LHC. The fine-tuning is still kept mild.

Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using s = 8 $$ \sqrt{s}=8 $$ TeV proton-proton collision data

A search for squarks and gluinos in final states containing high-$p_{\rm T}$ jets, missing transverse momentum and no electrons or muons is presented. The data were recorded in 2012 by the ATLAS experiment in $\sqrt{s}=8$ TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of $20.3 \mathrm{fb}^{-1}$. No significant excess above the Standard Model expectation is observed. Results are interpreted in a variety of simplified and specific supersymmetry-breaking models assuming that R-parity is conserved and that the lightest neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 1330 GeV for a simplified model incorporating only a gluino and the lightest neutralino. For a simplified model involving the strong production of first- and second-generation squarks, squark masses below 850 GeV (440 GeV) are excluded for a massless lightest neutralino, assuming mass degenerate (single light-flavour) squarks. In mSUGRA/CMSSM models with $\tan\beta=30$, $A_0=-2m_0$ and $\mu> 0$, squarks and gluinos of equal mass are excluded for masses below 1700 GeV. Additional limits are set for non-universal Higgs mass models with gaugino mediation and for simplified models involving the pair production of gluinos, each decaying to a top squark and a top quark, with the top squark decaying to a charm quark and a neutralino. These limits extend the region of supersymmetric parameter space excluded by previous searches with the ATLAS detector.

Higgs mediation with strong hidden sector dynamics

We present a simple model that achieves $m_h\approx 126$ GeV in the MSSM with large $A$-terms and TeV-scale stops through a combination of gauge mediation and Higgs-messenger interactions. The $\mu$/$B_\mu$ and $A$/$m_H^2$ problems are both solved by a common mechanism -- partial sequestering from strong hidden sector dynamics. Using the framework of General Messenger Higgs Mediation, we explicitly calculate the soft masses in terms of the vacuum expectation values, operator dimensions and OPE coefficients of the strongly-coupled hidden sector. Along the way, we also present a general analysis of the various constraints on sequestered Higgs mediation models. The phenomenology of such models is similar to gaugino mediation, but with large $A$-terms. The NLSP is always long-lived and is either the lightest stau or the Higgsino. The colored states are typically out of reach of the 8 TeV LHC, but may be accessible at 14 TeV, especially if the NLSP is the lightest stau.

Bino-Higgsino mixed dark matter in a focus point gaugino mediation

We investigate the neutralino dark matter in the focus point gaugino mediation model with the O(100) GeV gravitino. The thermal relic abundance of the neutralino with a sizable Higgsino fraction can explain the dark matter density at the present universe. The spin-independent cross section is marginally consistent with the current upper limit from the XENON 100 experiment, and the whole parameter region can be covered at the XENON1T experiment. We also discuss the origin of the gluino mass to wino mass ratio at around 3/8, which is crucial for the mild fine-tuning in the electroweak symmetry breaking sector. It is shown that the existence of the non-anomalous discrete R-symmetry can fix this ratio to 3/8.

Focus point in gaugino mediation — Reconsideration of the fine-tuning problem

We reconsider the fine-tuning problem in SUSY models, motivated by the recent observation of the relatively heavy Higgs boson and non-observation of the SUSY particles at the LHC. Based on this thought, we demonstrate a focus point-like behavior in a gaugino mediation model, and show that the fine-tuning is indeed reduced to about 2% level if the ratio of the gluino mass to wino mass is about 0.4 at the GUT scale. We show that such a mass ratio may arise naturally in a product group unification model without the doublet–triplet splitting problem. This fact suggests that the fine-tuning problem crucially depends on the physics at the high energy scale.

SO(10) GUT IN FOUR AND FIVE DIMENSIONS: A REVIEW

We review SO(10) grand unified theories (GUTs) in four and five dimensions (4D and 5D). The renormalizable minimal SO(10) SUSY GUT is the central theme of this paper. It is very predictive and makes it possible to construct all mass matrices including those of the Dirac and heavy right-handed Majorana neutrinos. Its predictions covers all ranges of particle phenomena. The explicit construction of the Higgs superpotential and the explicit display of a symmetry breaking pattern from GUT to the SM show that the naive desert from the SM to GUT in the minimal supersymmetric standard model (MSSM) is a too simplified concept and we have many definitely determined intermediate energy scales in general. This situation destroys the naive gauge coupling unification in the MSSM scheme. Also the precise measurements of neutrino oscillation data have revealed several small but manifest mismatches with our predictions. Also there are arguments that it is impossible to construct a GUT theory in 4D with a finite number of multiplets that leads to the MSSM with a residual R symmetry. If we try to solve all these pathologies comprehensively, it is very attractive for us to go into extra dimensions. Extra dimension may be either warped or flat. The fifth dimension, for simplicity, is compactified on the S1/(Z2) (warped) or on the S1/(Z2×Z′2) (flat) orbifold with two inequivalent branes at the orbifold fixed points. In the former warped case, intermediate energy scales are translated with the positions of Higgs fields in the bulk and the fundamental scheme of the MSSM is recovered. On the other hand, in the latter flat scenario, all matter and Higgs multiplets reside on the Pati–Salam (PS) brane where the PS symmetry is manifest. There the original renormalizability in Yukawa coupling is broken but its essential structures of mass matrices in minimal SO(10) GUT in 4D is promoted to the PS invariant action in 4D. In the gaugino mediation mechanism, the SO(10) gauge multiplet is transmitted to the PS brane through the gaugino mediation with bulk gauge multiplet. Further breaking of the PS gauge group to the SM group is realized by VEVs of the Higgs multiplets [Formula: see text]. We show that this model not only cures all pathologies in SO(10) GUT in 4D but also provides the consistent inflation scenario and dark matter candidate and leptogenesis. The gauge coupling unification is successfully realized after incorporating the threshold corrections of the Kaluza–Klein modes. Finally we add some comments on the impacts of the discovery of a Higgs-like particle by the Large Hadronic Collider at CERN (LHC) on SUSY GUTs.

Enhanced Higgs mass in a gaugino mediation model without the Polonyi problem

We consider a SUSY breaking scenario without the Polonyi problem. To solve the problem, the enhanced couplings of the Polonyi field to an inflaton, gauge kinetic functions and itself are assumed. As a result, a gaugino mediated SUSY breaking occurs. In this scenario, the Higgs boson mass becomes consistent with the recently observed value of the Higgs-like boson (i.e., mh≃125 GeV) for the gluino mass about 4 TeV, which is, however, out of the reach of the LHC experiment. We show that the trilinear coupling of the scalar top is automatically enhanced by the presence of the extra matters. With such extra matters, the Higgs mass as large as 125 GeV can be realized with the gluino mass of 1–2 TeV which is within the reach of the LHC experiment. In our scenario, the gravitino is the lightest SUSY particle and the candidate for dark matter, and the Wino, Bino, and sleptons are in the range from 200 GeV to 700 GeV.

An attractor for natural supersymmetry

We propose an attractor mechanism which generates the more minimal supersymmetric standard model from a broad class of supersymmetry breaking boundary conditions. The hierarchies in the fermion masses and mixings are produced by the same dynamics and a natural weak scale results from gaugino mediation. These features arise from augmenting the standard model with a new $SU(3)$ gauge group under which only the third generation quarks are charged. The theory flows to a strongly interacting fixed point which induces a negative anomalous dimension for the third generation quarks and a positive anomalous dimension for the Higgs. As a result, a split-family natural spectrum and the flavor hierarchies are dynamically generated.

Large, negative threshold contributions to light soft masses in models with effective supersymmetry

Threshold contributions to light scalar soft masses due to heavy sparticles (possibly including a heavy Higgs mostly aligned with H_d) in Effective SUSY scenarios are dominated by two-loop diagrams involving gauge couplings. This is due to the fact that in the limit in which the heavy states are degenerate, their one-loop contributions to the light soft masses only depend on small Yukawas and the hypercharge coupling. The two-loop threshold corrections involving only gauge couplings are calculated accounting for nonzero gaugino and light squark masses and shown to be negative, and rather large (\delta m^2_{t,L}\sim-480^2 GeV^2 for heavy sparticles with masses around 10 TeV). The effect on tachyon bounds is revisited with calculations implementing decoupling. It is pointed out that models yielding Effective SUSY spectra using gaugino mediation require in general very heavy gluinos or a very low SUSY breaking scale in order to avoid tachyons (e.g. for heavy squarks at 10 TeV and a SUSY breaking scale of 125 TeV, minimal scenarios require \tilde m_3 >=2 TeV at 500 GeV, while nonminimal ones demand \tilde m_3 >= 8 TeV).

Anatomy of maximal stop mixing in the MSSM

Abstract A Standard Model-like Higgs near 125 GeV in the MSSM requires multi-TeV stop masses, or a near-maximal contribution to its mass from stop mixing. We investigate the maximal mixing scenario, and in particular its prospects for being realized it in potentially realistic GUT models. We work out constraints on the possible GUT-scale soft terms, which we compare with what can be obtained from some well-known mechanisms of SUSY breaking mediation. Finally, we analyze two promising scenarios in detail, namely gaugino mediation and gravity mediation with non-universal Higgs masses.

Observing signals of the bulk matter Randall-Sundrum model through rare decays of supersymmetric particles

The bulk matter Randall-Sundrum (RS) model is a setup where standard model (SM) matter and gauge fields reside in the bulk of 5D warped spacetime while the Higgs field is confined on the IR brane. The wave functions of the 1st and 2nd generation matter particles are localized toward the UV brane and those of the 3rd generation toward the IR brane, so that the hierarchical structure of the Yukawa couplings arises geometrically without hierarchy in fundamental parameters. This paper discusses observing signals of this model in the case where the Kaluza-Klein scale is far above the collider scale, but the model is combined with the 5D minimal supersymmetric standard model (MSSM) and supersymmetric (SUSY) particles are in the reach of collider experiments. A general SUSY breaking mass spectrum consistent with the bulk matter RS model is considered: a SUSY breaking sector locates on the IR brane and its effects are mediated to 5D MSSM through a hybrid of gravity mediation, gaugino mediation, and gauge mediation. This paper argues that it is possible to observe the signals of the bulk matter RS model through rare decays of ``almost SU(2) singlet mass eigenstates'' that are induced by flavor-violating gravity mediation contributions to matter soft SUSY breaking terms.

A unified approach to supersymmetry breaking

General formulae for the soft SUSY breaking terms, valid in any SUGRA context, were derived in the mid-nineties. Since SUSY is not expected to have quantum anomalies, they should be valid in the quantum theory and be RG invariant down to the soft SUSY breaking scale. This observation enables us to give a uniform treatment of all phenomenological models for SUSY breaking and transmission, such as AMSB, GMSB, etc. In particular we find that the much discussed RG invariant formulae for soft SUSY breaking parameters in AMSB, effectively depend on a strong assumption of factorizability of the matter Kaehler metric. We then argue that there is no necessity for having ad hoc constructions such as mAMSB to counteract the negative squared slepton mass problem, since the natural framework that emerges in a sequestered model is one in which gaugino masses are as in AMSB, and the other soft terms are generated by RG running as in gaugino mediation.

On the spectrum of direct gaugino mediation

In direct gauge mediation, the gaugino masses are anomalously small, giving rise to a split SUSY spectrum. Here we investigate the superpartner spectrum in a minimal version of “direct gaugino mediation”. We find that the sfermion masses are comparable to those of the gauginos — even in the hybrid gaugino-gauge mediation regime — if the messenger scale is sufficiently small.

Gaugino mediation combined with the bulk matter Randall-Sundrum model

We investigate a simple 5D extension of the Minimal Supersymmetric (SUSY) Standard Model (SM) that is combined with the bulk matter Randall-Sundrum (RS) model, which gives a natural explanation the Yukawa coupling hierarchy. In this model, matter and gauge superfields reside in the 5D bulk while a SUSY breaking sector and the Higgs doublet superfields are localized on the infrared brane. The Yukawa coupling hierarchy in SM can be naturally explained through the wavefunction localization of the matter superfields. While sparticles obtain their flavor-blind soft SUSY breaking masses dominantly from the gaugino-mediated SUSY breaking, flavor-violating soft terms arise through the gravity-mediated SUSY breaking which are controlled by the wavefunction localization of the matter superfields. This structure of the model allows us to predict the sparticle mass spectrum including flavor-violating terms. We first explicitly determine the 5D disposition of matter superfields from the low-energy experimental data on SM fermion masses, CKM matrix and the neutrino oscillation parameters. Then, we calculate particle mass spectra and estimate the effects of the flavor-violating soft terms, which should be compared with the current experimental constraints. With gravitino being the lightest sparticle (LSP), the next-to-LSP, which is long-lived, is predicted most likely to be either singlet smuonlike or selectronlike. The model can be tested at collider experiments through flavor-violating processes involving sparticles. The flavor structure among sparticle, once observed, gives us a clue to deep understanding of the origin of Yukawa coupling hierarchy.

Sparticle Masses in a Supersymmetric Grand Unified Model

In this paper, we investigate the phenomenological aspect relevant to the sparticle masses of a supersymmetric grand unified model, in which the $SU(5)$ is used as the grand unified group with the minimal particle contents and supersymmetry breaking is mediated by the so-called gaugino mediation mechanism. A detailed analysis about the dependence of the squarks and sleptons masses on the free parameter space is given, and shown to be useful for the collider phenomenological study and parameter determination for future experiments.