Mediated SUSY Breaking Research Articles

Explanation of electron and muon g − 2 anomalies in AMSB

We propose to jointly explain the electron/muon g−2 anomalies in the framework of anomaly mediated SUSY breaking (AMSB) scenario. Two Yukawa deflected AMSB models are proposed and discussed in depth: one with lepton-specific interactions and the other one with messenger-matter interactions. Both models are found to be able to jointly explain the anomalies at 2σ level by naturally realizing the preferred parameter space with μM1,μM2<0 and very heavy left-handed smuon.

Low Energy Supersymmetry Confronted with Current Experiments: An Overview

This study provides a brief overview of low energy supersymmetry (SUSY) in light of current experimental constraints, such as collider searches, dark matter searches, and muon g−2 measurements. In addition, we survey a variety of low energy supersymmetric models: the phenomenological minimal supersymmetric model (MSSM); the supersymmetric models with cut-off-scale boundary conditions, i.e., the minimal supergravity (mSUGRA) or the constrained MSSM (CMSSM), the gauge mediation of SUSY breaking (GMSB), and the anomaly mediation of SUSY breaking (AMSB), as well as their extensions. The conclusion is that the low energy SUSY can survive all current experimental constraints and remains compelling, albeit suffering from a slight fine-tuning problem. The advanced models such as mSUGRA, GMSB, and AMSB need to be extended if the muon g−2 anomaly comes from new physics.

Phases of nonsupersymmetric gauge theories: The SO(Nc) case study

We investigate the IR phases of non-supersymmetric (non-SUSY) $SO(N_c)$ gauge theories with $N_F$ fermions in the vector representation obtained by perturbing the SUSY theory with anomaly mediated SUSY breaking (AMSB). We find that of the wide variety of phases appearing in the SUSY theory only two survive: for $N_F<\frac{3}{2} (N_c-2)$ the theory confines, breaking the $SU(N_F)$ global symmetry to $SO(N_F)$, while for $\frac{3}{2} (N_c-2)<N_F<3(N_c-2)$ the theory flows to a (super)-conformal fixed point. The abelian Coulomb and free magnetic phases do not survive and collapse to the confining phase. We also investigate the behavior of loop operators in order to provide a clear distinction between the confining and screened phases. With the choice of $Spin(N_c)$ for the global structure of the gauge group, we find that the electric Wilson loop indeed obeys an area law, providing one of the first demonstrations of true confinement with chiral symmetry breaking in a non-SUSY theory. We identify monopole condensation as the dynamics underlying confinement. These monopoles arise naturally for $N_F=N_c-2$. The case with smaller number of flavors can be obtained by integrating out flavors, and we confirm numerically that the monopole condensate persists in the presence of AMSB and mass perturbations.

The upper bound of the second Higgs boson mass in minimal gauge mediation with the gravitino warm dark matter

A keV-scale gravitino arising from a minimal supersymmetric (SUSY) Standard Model (MSSM) is an interesting possibility since the small scale problems that the ΛCDM model encounters in the modern cosmology could be alleviated with the keV-scale gravitino serving as the warm dark matter (WDM). Such a light gravitino asks for a low scale supersymmetry (SUSY) breaking for which the gauge mediation (GM) is required as a consistent SUSY-breaking mediation mechanism. In this paper, we show upper bounds of the masses of the second CP-even Higgs boson H and the CP-odd Higgs boson A, assuming the keV-scale gravitino to be responsible for the current DM relic abundance: the upper bound on the mass of H/A is found to be ∼ 4 TeV for the gravitino mass of mathcal{O}left(10-100right) keV. Interestingly, the mass of H/A can be as small as 2–3 TeV and the predicted tan β is as large as 55–60 for the gravitino mass of mathcal{O}(10) keV. This will be tested in the near future Large Hadron Collider (LHC) experiments.

SUSY breaking constraints on modular flavor S3 invariant SU(5) GUT model

Modular flavor symmetry can be used to explain the quark and lepton flavor structures. The SUSY partners of quarks and leptons, which share the same superpotential with the quarks and leptons, will also be constrained by the modular flavor structure and show a different flavor(mixing) pattern at the GUT scale. So, in realistic modular flavor models with SUSY completion, constraints from the collider and DM constraints can also be used to constrain the possible values of the modulus parameter. In the first part of this work, we discuss the possibility that the S3 modular symmetry can be preserved by the fixed points of T2/ZN orbifold, especially from T2/Z2. To illustrate the additional constraints from collider etc on modular flavor symmetry models, we take the simplest UV SUSY-completion S3 modular invariance SU(5) GUT model as an example with generalized gravity mediation SUSY breaking mechanism. We find that such constraints can indeed be useful to rule out a large portion of the modulus parameters. Our numerical results show that the UV-completed model can account for both the SM (plus neutrino) flavor structure and the collider, DM constraints. Such discussions can also be applied straightforwardly to other modular flavor symmetry models, such as A4 or S4 models.

Minimal Yukawa deflection of AMSB from the Kahler potential

We propose a minimal Yukawa deflection scenario of AMSB from the Kahler potential through the Higgs-messenger mixing. Salient features of this scenario are discussed and realistic MSSM spectrum can be obtained. Such a scenario, which are very predictive, can solve the tachyonic slepton problem with less messenger species. Numerical results indicate that the LOSPs predicted by this scenario can not be good DM candidates. So it is desirable to extend this scenario with a Peccei-Quinn sector to solve the strong CP problem and at the same time provide new DM candidates. We propose a way to obtain a light axino mass in SUSY KSVZ axion model with Yukawa deflected anomaly mediation SUSY breaking mechanism. The axino can possibly be the LSP and act as a good DM candidate.

Starobinsky-like inflation and soft-SUSY breaking

We study a version of Starobinsky-like inflation in no-scale supergravity (SUGRA) where a Polonyi term in the hidden sector breaks supersymmetry (SUSY) after inflation, providing a link between the gravitino mass and inflation. We extend the theory to the visible sector and calculate the soft-SUSY breaking parameters depending on the modular weights in the superpotential and choice of Kähler potential. We are led to either no-scale SUGRA or pure gravity mediated SUSY breaking patterns, but with inflationary constraints on the Polonyi term setting a strict upper bound on the gravitino mass m3/2< 103 TeV. Since gaugino masses are significantly lighter than m3/2, this suggests that SUSY may be discovered at the LHC or FCC.

Solving the muon g-2 anomaly in CMSSM extension with non-universal gaugino masses

We propose to generate non-universal gaugino masses in SU(5) Grand Unified Theory (GUT) with the generalized Planck-scale mediation SUSY breaking mechanism, in which the non-universality arises from proper wavefunction normalization with lowest component VEVs of various high dimensional representations of the Higgs fields of SU(5) and an unique F-term VEV by the singlet. Different predictions on gaugino mass ratios with respect to widely studied scenarios are given. The gluino-SUGRA-like scenario, where gluinos are much heavier than winos, bino and universal scalar masses, can be easily realized with appropriate combinations of such high-representation Higgs fields. With six GUT-scale free parameters in our scenario, we can solve elegantly the tension between mSUGRA and the present experimental results, including the muon g-2, the dark matter (DM) relic density and the direct sparticle search bounds from the LHC. Taking into account the current constraints in our numerical scan, we have the following observations: (i) The large-tan β (≳35) samples with a moderate M3 (∼5 TeV), a small |A0/M3| (≲0.4) and a small mA (≲4 TeV) are favoured to generate a 125 GeV SM-like Higgs and predict a large muon g-2, while the stop mass and μ parameter, mainly determined by |M3| (≫ M0, |M1|, |M2|), can be about 6 TeV; (ii) The moderate-tan β (35 ∼ 40) samples with a negative M3 can have a light smuon (250 ∼ 450 GeV) but a heavy stau (≳1 TeV), which predict a large muon g-2 but a small Br(Bs → μ+μ−); (iii) To obtain the right DM relic density, the annihilation mechanisms should be stau exchange, stau coannihilation, chargino coannihilation, slepton annihilation and the combination of two or three of them; (iv) To obtain the right DM relic density, the spin-independent DM-nucleon cross section is typically much smaller than the present limits of XENON1T 2018 and also an order of magnitude lower than the future detection sensitivity of LZ and XENONnT experiments.

NMSSM from alternative deflection in generalized deflected anomaly mediated SUSY breaking

We propose a new approach to generate messenger–matter interactions in deflected anomaly mediated SUSY breaking mechanism from typical holomorphic messenger–matter mixing terms in the Kahler potential. This approach is a unique feature of AMSB and has no analog in GMSB-type scenarios. New coupling strengths from the scaling of the (already known) Yukawa couplings always appear in this approach. With messenger–matter interactions in deflected AMSB, we can generate a realistic soft SUSY breaking spectrum for next-to-minimal supersymmetric standard model (NMSSM). Successful electroweak symmetry breaking conditions, which is not easy to satisfy in NMSSM for ordinary AMSB-type scenario, can be satisfied in a large portion of parameter space in our scenarios. We study the relevant phenomenology for scenarios with (Bino-like) neutralino and axino LSP, respectively. In the case of axino LSP, the SUSY contributions to Delta a_mu can possibly account for the muon g-2 discrepancy. The corresponding gluino masses, which are found to below 2.2 TeV, could be tested soon at LHC.

Solving the muon g−2 anomaly in deflected anomaly mediated SUSY breaking with messenger-matter interactions

We proposed to introduce general messenger-matter interactions in the deflected anomaly mediated SUSY breaking scenario to explain the $g_\mu-2$ anomaly. Scenarios with complete or incomplete GUT multiplet messengers are discussed, respectively. The introduction of incomplete GUT mulitiplets can be advantageous in various aspects. We found that the $g_\mu-2$ anomaly can be solved in both scenarios under current constraints including the gluino mass bounds, while the scenarios with incomplete GUT representation messengers are more favored by the $g_\mu-2$ data. We also found that the gluino is upper bounded by about 2.5 TeV (2.0 TeV) in Scenario A and 3.0 TeV (2.7 TeV) in Scenario B if the generalized deflected AMSB scenarios are used to fully account for the $g_\mu-2$ anomaly at $3\sigma$ ($2\sigma$) level. Such a gluino should be accessible in the future LHC searches. Dark matter constraints, including DM relic density and direct detection bounds, favor the scenario B with incomplete GUT multiplets. Much of the allowed parameter space for the scenario B could be covered by the future DM direct detection experiments.

New type of charged Q -ball dark matter in gauge mediated SUSY breaking models

We examined the viability of a new type of charged $Q$-ball dark matter scenario. We considered the case where the relics can be treated as ordinary ions, to which we applied the observational constraint from the MICA experiment, where no trail of heavy ionlike object is observed in $1{0}^{9}$ year-old ancient muscovite mica. We have found that the allowed parameter region exists but is smaller than the neutral $Q$-ball dark matter case. We have also discussed whether our scenario is actually consistent with Affleck-Dine mechanism.

SUSY dark matter in universal and nonuniversal gaugino mass models

We review the phenomenology of SUSY dark matter in various versions of MSSM, with universal and nonuniversal gaugino masses at the GUT scale. We start with the universal case (CMSSM), where the cosmologically compatible dark matter relic density is achieved only over some narrow regions of parameter space, involving some fine-tuning. Moreover, most of these regions are seriously challenged by the constraints from collider and direct dark matter detection experiments. Then we consider some simple and predictive nonuniversal gaugino mass models, based on SU(5) GUT. Several of these models offer viable SUSY dark matter candidates, which are compatible with the cosmic dark matter relic density and the above mentioned experimental constraints. They can be probed at the present and future collider and dark matter search experiments. Finally, we consider the nonuniversal gaugino mass model arising from anomaly mediated SUSY breaking. In this case the cosmologically compatible dark matter relic density requires dark matter mass of a few TeV, which puts it beyond the scope of collider and direct dark matter detection experiments. However, it has interesting predictions for some indirect dark matter detection experiments.

Effective theories of flavor and the nonuniversal MSSM

Flavor symmetries \`{a} la Froggatt-Nielsen~(FN) provide a compelling way to explain the hierarchies of fermionic masses and mixing angles in the Yukawa sector. In Supersymmetric~(SUSY) extensions of the Standard Model where the mediation of SUSY breaking occurs at scales larger than the breaking of flavor, this symmetry must be respected not only by the Yukawas of the superpotential, but by the soft-breaking masses and trilinear terms as well. In this work we show that contrary to naive expectations, even starting with completely flavor blind soft-breaking in the full theory at high scales, the low-energy sfermion mass matrices and trilinear terms of the effective theory, obtained upon integrating out the heavy mediator fields, are strongly non-universal. We explore the phenomenology of these SUSY flavor models after the latest LHC searches for new physics.

Supersoft supersymmetry, conformal sequestering, and single scale supersymmetry breaking

Supersymmetric Standard Models (SSMs) with Dirac gauginos have the appealing supersoft property that they only cause finite contributions to scalar masses. Considering gauge mediated SUSY breaking with conformal sequestering and assuming there is one and only one fundamental parameter with dimension mass arising from supersymmetry breaking, we find a cancellation between the dominant terms that contribute to the EWFT. The resulting EWFT measure can be of order one even for supersymmetric particle masses and $\mu$-terms in the TeV range.

Long-Lived Gluinos and Stable Axinos.

In this Letter we present a novel version of "long-lived" gluinos in supersymmetric models with the gluino lightest ordinary supersymmetric particle (LOSP) and the axino lightest supersymmetric particle. Within certain ranges of the axion decay constant f_{a}<1×10^{10} GeV, the gluino mass bounds are reduced to less than 1000GeV. The best limits can be obtained by looking for decaying R hadrons in the detector where the gluino decays to a gluon and axino in the calorimeters. Supersymmetry (SUSY) models with a gluino LOSP can occur over a significant region of parameter space in either mirage mediation or general gauge-mediated SUSY breaking models. The gluino LOSP is not constrained by cosmology, but in this scenario the axion or axino may be a good dark matter candidate.

Deflected anomaly mediated SUSY breaking scenario with general messenger–matter interactions

We propose to introduce general messenger–matter interactions in the deflected anomaly mediated SUSY breaking scenario. The most general form for the resulting soft parameters is derived. New interference terms between the GMSB type and AMSB type contributions are the unique feature of this scenario. Messenger–matter interactions involving sleptons can be used to solve the tachyonic slepton problem and naturally lead to positive slepton masses regardless of the sign of deflection parameter. Besides, due to the new contributions, large |At| that will not trigger color-breaking stop VEV are also possible in this scenario, thus can easily give the 125 GeV higgs which was discovered by LHC. This type of deflected AMSB scenario need very few messenger species, thus can avoid possible non-perturbative gauge couplings below the GUT scale (or Landau pole below the Planck scale).

Naturalness-guided gluino mass bound from the minimal mixed mediation of SUSY breaking

In order to significantly reduce the fine-tuning associated with the electroweak symmetry breaking in the minimal supersymmetric standard model (MSSM), we consider not only the minimal gravity mediation effects but also the minimal gauge mediation ones for a common supersymmetry breaking source at a hidden sector. In this "Minimal Mixed Mediation model," the minimal forms for the Kahler potential and the gauge kinetic function are employed at tree level. The MSSM gaugino masses are radiatively generated through the gauge mediation. Since a "focus point" of the soft Higgs mass parameter, m_{h_u}^2 appears around 3-4 TeV energy scale in this case, m_{h_u}^2 is quite insensitive to stop masses. Instead, the naturalness of the small m_{h_u}^2 is more closely associated with the gluino mass rather than the stop mass unlike the conventional scenario. As a result, even a 3-4 TeV stop mass, which is known to explain the 125 GeV Higgs mass at three-loop level, can still be compatible with the naturalness of the electroweak scale. On the other hand, the requirements of various fine-tuning measures much smaller than 100 and |\mu| < 600 GeV constrain the gluino mass to be 1.6 TeV < M_3 < 2.2 TeV, which is well-inside the discovery potential range of LHC RunII.

Towards the natural gauge mediation

The sweet spot supersymmetry (SUSY) solves the μ/B μ problem in the Minimal Supersymmetric Standard Model (MSSM) with gauge mediated SUSY breaking (GMSB) via the generalized Giudice-Masiero (GM) mechanism where only the μ-term and soft Higgs masses are generated at the unification scale of the Grand Unified Theory (GUT) due to the approximate PQ symmetry. Because all the other SUSY breaking soft terms are generated via the GMSB below the GUT scale, there exists SUSY electroweak (EW) fine-tuning problem to explain the 125 GeV Higgs boson mass due to small trilinear soft term. Thus, to explain the Higgs boson mass, we propose the GMSB with both the generalized GM mechanism and Higgs-messenger interactions. The renormalization group equations are runnings from the GUT scale down to EW scale. So the EW symmetry breaking can be realized easier. We can keep the gauge coupling unification and solution to the flavor problem in the GMSB, as well as solve the μ/B μ -problem. Moreover, there are only five free parameters in our model. So we can determine the characteristic low energy spectra and explore its distinct phenomenology. The fine-tuning measure can be as low as 100. For some benchmark points, the stop mass can be as low as 1.7 TeV while the glunio mass is around 2.5 TeV. The gravitino dark matter can come from a thermal production with the correct relic density and be consistent with the thermal leptogenesis. Because gluino and stop can be relatively light in our model, how to search for such GMSB at the upcoming run II of the LHC experiment could be very interesting.

ChargedQ-balls in gauge mediated SUSY breaking models

It is known that after Affleck-Dine baryogenesis, spatial inhomogeneities of Affleck-Dine field grow into non-topological solitons called Q-balls. In gauge mediated SUSY breaking models, sufficiently large Q-balls with baryon charge are stable while Q-balls with lepton charge can always decay into leptons. For a Q-ball that carries nonzero $B$ and $L$ charges, the difference between the baryonic component and the leptonic component in decay rate may induce nonzero electric charge on the Q-ball. This implies that charged Q-ball, also called gauged Q-ball, may emerge in our universe. In this paper, we investigate two complex scalar fields, a baryonic scalar field and a leptonic one, in an Abelian gauge theory. We find stable solutions of gauged Q-balls for different baryon and lepton charges. Those solutions shows that a Coulomb potential arises and the Q-ball becomes electrically charged as expected. It is energetically favored that some amount of leptonic component decays, but there is an upper bound on its amount due to the Coulomb force. The baryonic decay also becomes possible by virtue of electrical repulsion and we find the condition to suppress it so that the charged Q-balls can survive in the universe.

Muon g − 2 in anomaly mediated SUSY breaking

Motivated by two experimental facts, the muon g-2 anomaly and the observed Higgs boson mass around 125 GeV, we propose a simple model of anomaly mediation, which can be seen as a generalization of mixed modulus-anomaly mediation. In our model, the discrepancy of the muon g-2 and the Higgs boson mass around 125 GeV are easily accommodated. The required mass splitting between the strongly and weakly interacting SUSY particles are naturally achieved by the contribution from anomaly mediation. This model is easily consistent with SU(5) or SO(10) grand unified theory.