Soft Supersymmetry-breaking Masses Research Articles

Flavor- and CP-safe explanation of gμ − 2 anomaly

Supersymmetry is still a viable explanation for the muon g – 2 anomaly, if the sleptons and electroweak gauginos are mathcal{O}(100) GeV. However, for supersymmetry breaking masses this light, the SUSY flavor and CP-problem are exacerbated. To address this issue, we consider a flavor-safe gauge mediated explanation of the muon g – 2 with additional Higgs soft supersymmetry breaking mass parameters. The setup provides a generic parameter space within minimal gauge mediation. Furthermore, we show that the problematic CP violating phase can be dynamically suppressed. We find that gauge mediation models have large portions of parameter space where the muon g – 2 can be explained at 1 σ level. The interplay between the slepton and the CP-odd Higgs masses also makes the majority of this model’s parameter space testable at the LHC through searches for sleptons or additional Higgs bosons.

Flavored gauge-mediated supersymmetry breaking models with discrete non-Abelian symmetries

We investigate flavored gauge mediation models in which the Higgs and messenger doublets are embedded in multiplets of the discrete non-Abelian symmetry ${\mathcal{S}}_{3}$. In these theories, the ${\mathcal{S}}_{3}$ symmetry correlates the flavor structure of the quark and lepton Yukawa couplings with the structure of the messenger Yukawa couplings that contribute to the soft supersymmetry breaking mass parameters. We provide a systematic exploration of possible scenarios within this framework that can accommodate hierarchical quark and charged lepton masses, and examine the resulting phenomenological implications in each case. We find a heavier spectrum for the superpartner masses compared to flavored gauge mediation models controlled by Abelian symmetries, which can be directly traced back to the need in our scenarios for two vectorlike pairs of messenger fields for viable electroweak symmetry breaking.

Flipped SU(5) GUT phenomenology: proton decay and mathbf {g_mu - 2}

We consider proton decay and g_mu - 2 in flipped SU(5) GUT models. We first study scenarios in which the soft supersymmetry-breaking parameters are constrained to be universal at some high scale M_{in} above the standard GUT scale where the QCD and electroweak SU(2) couplings unify. In this case the proton lifetime is typically > rsim 10^{36} years, too long to be detected in the foreseeable future, and the supersymmetric contribution to g_mu - 2 is too small to contribute significantly to resolving the discrepancy between the experimental measurement and data-driven calculations within the Standard Model. However, we identify a region of the constrained flipped SU(5) parameter space with large couplings between the 10- and 5-dimensional GUT Higgs representations where p rightarrow e^+ pi ^0 decay may be detectable in the Hyper-Kamiokande experiment now under construction, though the contribution to g_mu -2 is still small. A substantial contribution to g_mu - 2 is possible, however, if the universality constraints on the soft supersymmetry-breaking masses are relaxed. We find a ‘quadrifecta’ region where observable proton decay co-exists with a (partial) supersymmetric resolution of the g_mu - 2 discrepancy and acceptable values of m_h and the relic LSP density.

Flipped mathbf {g_mu - 2}

We analyze the possible magnitude of the supersymmetric contribution to g_mu - 2 in a flipped SU(5) GUT model. Unlike other GUT models which are severely constrained by universality relations, in flipped SU(5) the U(1) gaugino mass and the soft supersymmetry-breaking masses of right-handed sleptons are unrelated to the other gaugino, slepton and squark masses. Consequently, the lightest neutralino and the right-handed smuon may be light enough to mitigate the discrepancy between the experimental measurement of g_mu - 2 and the Standard Model calculation, in which case they may be detectable at the LHC and/or a 250 GeV e^+ e^- collider, whereas the other gauginos and sfermions are heavy enough to escape detection at the LHC.

Low-energy probes of no-scale SU(5) super-GUTs

We explore the possible values of the mu rightarrow e gamma branching ratio, text {BR}(mu rightarrow egamma ), and the electron dipole moment (eEDM), d_e, in no-scale SU(5) super-GUT models with the boundary conditions that soft supersymmetry-breaking matter scalar masses vanish at some high input scale, M_mathrm{in}, above the GUT scale, M_{mathrm{GUT}}. We take into account the constraints from the cosmological cold dark matter density, Omega _{CDM} h^2, the Higgs mass, M_h, and the experimental lower limit on the lifetime for p rightarrow K^+ bar{nu }, the dominant proton decay mode in these super-GUT models. Reconciling this limit with Omega _{CDM} h^2 and M_h requires the Higgs field responsible for the charge-2/3 quark masses to be twisted, and possibly also that responsible for the charge-1/3 and charged-lepton masses, with model-dependent soft supersymmetry-breaking masses. We consider six possible models for the super-GUT initial conditions, and two possible choices for quark flavor mixing, contrasting their predictions for proton decay with versions of the models in which mixing effects are neglected. We find that tau left( prightarrow K^+ bar{nu }right) may be accessible to the upcoming Hyper-Kamiokande experiment, whereas all the models predict text {BR}(mu rightarrow egamma ) and d_e below the current and prospective future experimental sensitivities or both flavor choices, when the dark matter density, Higgs mass and current proton decay constraints are taken into account. However, there are limited regions with one of the flavor choices in two of the models where mu rightarrow e conversion on a heavy nucleus may be observable in the future. Our results indicate that there is no supersymmetric flavor problem in the class of no-scale models we consider.

Muon g \u2212 2 in Higgs-anomaly mediation

A simple model for the explanation of the muon anomalous magnetic moment was proposed by the present authors within the context of the minimal supersymmetric standard model [1, 2]: Higgs-anomaly mediation. In the setup, squarks, sleptons, and gauginos are massless at tree-level, but the Higgs doublets get large negative soft supersymmetry (SUSY) breaking masses squared {m}_{H_u}^2simeq {m}_{H_d}^2<0 at a certain energy scale, Minp. The sfermion masses are radiatively generated by anomaly mediation and Higgs-loop effects, and gaugino masses are solely determined by anomaly mediation. Consequently, the smuons and bino are light enough to explain the muon g − 2 anomaly while the third generation sfermions are heavy enough to explain the observed Higgs boson mass. The scenario avoids the SUSY flavor problem as well as various cosmological problems, and is consistent with the radiative electroweak symmetry breaking. In this paper, we show that, although the muon g − 2 explanation in originally proposed Higgs-anomaly mediation with Minp∼ 1016 GeV is slightly disfavored by the latest LHC data, the muon g − 2 can still be explained at 1σ level when Higgs mediation becomes important at the intermediate scale, Minp∼ 1012 GeV. The scenario predicts light SUSY particles that can be fully covered by the LHC and future collider experiments. We also provide a simple realization of {m}_{H_u}^2simeq {m}_{H_d}^2<0 at the intermediate scale.

A minimal SU(5) SuperGUT in pure gravity mediation

The lack of evidence for low-scale supersymmetry suggests that the scale of supersymmetry breaking may be higher than originally anticipated. However, there remain many motivations for supersymmetry including gauge coupling unification and a stable dark matter candidate. Models like pure gravity mediation (PGM) evade LHC searches while still providing a good dark matter candidate and gauge coupling unification. Here, we study the effects of PGM if the input boundary conditions for soft supersymmetry breaking masses are pushed beyond the unification scale and higher dimensional operators are included. The added running beyond the unification scale opens up the parameter space by relaxing the constraints on tan beta . If higher dimensional operators involving the SU(5) adjoint Higgs are included, the mass of the heavy gauge bosons of SU(5) can be suppressed leading to proton decay, prightarrow pi ^0 e^+, that is within reach of future experiments. Higher dimensional operators involving the supersymmetry breaking field can generate additional contributions to the A- and B-terms of order m_{3/2}. The threshold effects involving these A- and B-terms significantly impact the masses of the gauginos and can lead to a bino LSP. In some regions of parameter space the bino can be degenerate with the wino or gluino and give an acceptable dark matter relic density.

An extended gauge mediation for muon (g − 2) explanation

It is increasingly becoming difficult, within a broad class of supersymmetric models, to satisfactorily explain the discrepancy between the measured (g−2)μ and its standard model prediction, and at the same time satisfy all the other constraints. In this paper we propose a new scheme of gauge mediation by introducing new soft supersymmetry breaking mass parameters for the Higgs sector in a minimal setup containing only a pair of (5+5¯) messenger fields of SU(5). This enables us to explain the (g−2)μ discrepancy while avoiding all the existing constraints. We also provide possible dynamical origin of the new soft mass parameters. The wino and higgsino weighing below 500 GeV constitute the smoking gun signal at the (high luminosity) LHC.

Effective field theory of integrating out sfermions in the MSSM: Complete one-loop analysis

We apply the covariant derivative expansion of the Coleman-Weinberg potential to the sfermion sector in the minimal supersymmetric standard model, matching it to the relevant dimension-6 operators in the standard model effective field theory at one-loop level. Emphasis is paid to nondegenerate large soft supersymmetry breaking mass squares, and the most general analytical Wilson coefficients are obtained for all pure bosonic dimension-6 operators. In addition to the non-logarithmic contributions, they generally have another logarithmic contributions. Various numerical results are shown, in particular the constraints in the large $X_t$ branch reproducing the $125$~GeV Higgs mass can be pushed to high values to almost completely probe the low stop mass region at the future FCC-ee experiment, even given the Higgs mass calculation uncertainty.

Possible Approach to Dynamical Supersymmetry Breaking via Nambu-Jona-Lasinio Model

Supersymmetry is undoubtedly a popular candidate for physics beyond the Standard Model. However, the origin of soft supersymmetry breaking masses has been usually depicted intricately in the literature via extra hidden/mediating sectors. Thus, a simple theory for the generation of the soft masses would be more compelling. Here we discuss a possible approach to dynamical supersymmetry breaking via Nambu-Jona- Lasinio (NJL) Model, which has been missed since the first investigation of supersymmetric NJL model. We introduce a four-superfield interaction term that induces a real two-superfield composite with vacuum condensate. The latter has supersymmetry breaking parts, which we show to bear nontrivial solutions following a standard nonperturbative analysis for a NJL type model. The presence of the expected Goldstino state along with the supersymmetry breaking, is also verified. Moreover, the model gives rise to a composite spin one field, as its important characteristic.

Scale hierarchies in particle physics and cosmology

I describe the phenomenology of a model of supersymmetry breaking in the presence of a tiny (tuneable) positive cosmological constant. It utilises a single chiral multiplet with a gauged shift symmetry, that can be identified with the string dilaton (or an appropriate compactification modulus). The model is coupled to the MSSM, leading to calculable soft supersymmetry breaking masses and a distinct low energy phenomenology that allows to differentiate it from other models of supersymmetry breaking and mediation mechanisms. We also study the question if this model can lead to inflation by identifying the dilaton with the inflaton. We find that this is possible if the Kähler potential is modified by a term that has the form of NS5-brane instantons, leading to an appropriate inflationary plateau around the maximum of the scalar potential, depending on two extra parameters.

Scale hierarchies and string cosmology

I describe the phenomenology of a model of supersymmetry breaking in the presence of a tiny (tuneable) positive cosmological constant. It utilizes a single chiral multiplet with a gauged shift symmetry, that can be identified with the string dilaton (or an appropriate compactification modulus). The model is coupled to the MSSM, leading to calculable soft supersymmetry breaking masses and a distinct low energy phenomenology that allows to differentiate it from other models of supersymmetry breaking and mediation mechanisms. We also study the question if this model can lead to inflation by identifying the dilaton with the inflaton. We find that this is possible if the Kähler potential is modified by a term that has the form of NS5-brane instantons, leading to an appropriate inflationary plateau around the maximum of the scalar potential, depending on two extra parameters.

Muon g−2 in gauge mediated supersymmetry breaking models with adjoint messengers

We explored the sparticle mass spectrum in light of the muon g-2 anomaly and the little hierarchy problem in a class of gauge mediated supersymmetry breaking model. Here the messenger fields transform in the adjoint representation of the Standard Model gauge symmetry. To avoid unacceptably light right-handed slepton masses the standard model is supplemented by additional U(1)_B-L gauge symmetry. Considering a non-zero U(1)_B-L D-term leads to an additional contribution to the soft supersymmetry breaking mass terms which makes the right-handed slepton masses compatible with the current experimental bounds. We show that in the framework of Lambda_{3}<0 and mu < 0, the muon g-2 anomaly and the observed 125 GeV Higgs boson mass a can be simultaneously accommodated. The slepton masses in this case are predicted to lie in the few hundred GeV range, which can be tested at LHC. Despite the heavy colored spectrum the the little hierarchy problem in this model can be ameliorated and electroweak fine tuning parameter can be as low as 10 or so.

Gauge mediation models with adjoint messengers

We present a class of models in the framework of gauge mediation supersymmetry breaking where the messenger fields transform in the adjoint representation of the Standard Model gauge symmetry. To avoid unacceptably light right-handed sleptons in the spectrum we introduce a non-zero U(1)_B-L D-term. This leads to an additional contribution to the soft supersymmetry breaking mass terms which makes the right-handed slepton masses compatible with the current experimental bounds. We show that in this framework the observed 125 GeV Higgs boson mass can be accommodated with the sleptons accessible at the LHC, while the squarks and gluinos lie in the multi-TeV range. We also discuss the issue of the fine-tuning and show that the desired relic dark matter abundance can also be accommodated.

The minimal SUSY B − L model: simultaneous Wilson lines and string thresholds

In previous work, we presented a statistical scan over the soft supersymmetry breaking parameters of the minimal SUSY $B-L$ model. For specificity of calculation, unification of the gauge parameters was enforced by allowing the two ${\mathbb Z}_{3}\times {\mathbb Z}_{3}$ Wilson lines to have mass scales separated by approximately an order of magnitude. This introduced an additional "left-right" sector below the unification scale. In this paper, for three important reasons, we modify our previous analysis by demanding that the mass scales of the two Wilson lines be simultaneous and equal to an "average unification" mass $\left<M_{U}\right>$. The present analysis is 1) more "natural" than the previous calculations, which were only valid in a very specific region of the Calabi-Yau moduli space, 2) the theory is conceptually simpler in that the left-right sector has been removed and 3) in the present analysis the lack of gauge unification is due to threshold effects--particularly heavy string thresholds, which we calculate statistically in detail. As in our previous work, the theory is renormalization group evolved from $\left<M_{U}\right>$ to the electroweak scale--being subjected, sequentially, to the requirement of radiative $B-L$ and electroweak symmetry breaking, the present experimental lower bounds on the $B-L$ vector boson and sparticle masses, as well as the lightest neutral Higgs mass of $\sim$125 GeV. The subspace of soft supersymmetry breaking masses that satisfies all such constraints is presented and shown to be substantial.

A new scheme for NMSSM in gauge mediation

We propose a new framework for the next-to-minimal supersymmetric standard model (NMSSM) in gauge mediation, where in general the correct electroweak symmetry breaking (EWSB) is difficult to be explained. The difficulty is caused by the absence of a soft supersymmetry (SUSY) breaking mass for the NMSSM singlet S. In our framework, S is a meson in a hidden QCD. This QCD is responsible for the dynamical SUSY breaking, forming S, and the soft SUSY breaking mass for S, which is a key to explain the correct EWSB: all the ingredients for successful phenomenology originate from the common dynamics. From the requirement of the successful EWSB, the low-scale SUSY breaking around 100-1000 TeV is predicted. This is favored to avoid the large fine-tuning.

Scale Hierarchies in Particle Physics and Cosmology

We discuss possible connections between several scales in particle physics andcosmology, such the the electroweak, inflation, dark energy and Planck scales. We thendescribe the phenomenology of a model of supersymmetry breaking in the presence ofa tiny (tunable) positive cosmological constant. The model is coupled to the MSSM, leading to calculable soft supersymmetry breaking masses and a distinct low energy phenomenologythat allows to differentiate it from other models of supersymmetry breakingand mediation mechanisms.

Reconciling the muong−2, a 125 GeV Higgs boson, and dark matter in gauge mediation models

We present a class of models in the framework of gauge mediation supersymmetry breaking where the standard model is supplemented by additional U(1) symmetry which acts only on the third generation fermions. The messenger fields carry non-trivial U(1) charge and are vector-like particles under this symmetry. This leads to additional contribution to the soft supersymmetry breaking mass terms for the third generation squarks and sleptons. In this framework we show that the muon g-2 anomaly, the observed 125 GeV Higgs boson mass and the detected relic dark matter abundance (gravitino in our case) can be simultaneously accommodated. The resolution of the muon g-2 anomaly, in particular, yields the result that the first two generation squark masses, as well the gluino mass, should be <~ 2.5 TeV, which will be tested at LHC14.

MSSM soft terms from supergravity with gauged R-symmetry in de Sitter vacuum

We work out the phenomenology of a model of supersymmetry breaking in the presence of a tiny (tunable) positive cosmological constant, proposed by the authors in arXiv:1403.1534. It utilizes a single chiral multiplet with a gauged shift symmetry that can be identified with the string dilaton (or an appropriate compactification modulus). The model is coupled to the MSSM, leading to calculable soft supersymmetry breaking masses and a distinct low energy phenomenology that allows to differentiate it from other models of supersymmetry breaking and mediation mechanisms.

The effective MSSM

We suggest an effective field theory framework to discuss deviations from the minimal supersymmetric Standard Model (MSSM) which is based on an alternative arrangement of the gauge-Higgs sector. In this effective MSSM (EffMSSM) nonlinearly realised SU(2)×U(1) gauge sector is described by an SU(2)×U(1)-valued massive vector superfield, which contains a neutral CP-even and charged Higgs fields, while another neutral CP-even Higgs and the neutral CP-odd Higgs fields are residing in an SU(2)×U(1)-singlet chiral superfield. Although the new theory contains the same particle content as the conventional MSSM, the unconventional representation of superfields allows for new type of interactions, which may lead to a significant modification of the phenomenology. As an illustrative example we consider EffMSSM with modified Higgs and electroweak gauge sector augmented by gaugino soft supersymmetry breaking masses, Mi (i=1,2,3) and the Standard Higgs soft-breaking masses, mHu=mHd and Bμ, and point out distinct features in the Higgs and gaugino sectors as compared to MSSM. In particular, we show that the lightest neutral CP-even Higgs boson with mass ∼125GeV can be easily accommodated within EffMSSM.