We calculate the strength of the electroweak phase transition in a supersymmetric model with four chiral generations. The additional chiral fermions (and scalar partners) lower the critical temperature and thus strengthen the first-order phase transition. The scalar partners stabilize the potential, leading to an effective theory that is bounded from below. We identify the ensemble of parameters where phi_c/T_c \gsim 1 simultaneous with obtaining a large enough Higgs mass. Our calculations focus on a subset of the full four generational supersymmetric parameter space: We take the pseudoscalar heavy, tan(beta)=1, and neglect all subleading contributions to the effective potential. We find that the region of parameter space with a strong first-order phase transition requires m_tilde{q}'/m_q' \lsim 1.1 while the constraint on the lightest Higgs mass requires m_tilde{q}'/m_q' /gsim 1 with m_q' \gsim 300 GeV. We are led to an intriguing prediction of quarks and squarks just beyond the current Tevatron direct search limits that are poised to be discovered quickly at the LHC.
Inspired by the phenomenological constraints, LHC supersymmetry and Higgs searches, dark matter search as well as string model building, we propose the electroweak supersymmetry around the electroweak scale: the squarks and/or gluinos are around a few TeV while the sleptons, sneutrinos, bino and winos are within one TeV. The Higgsinos can be either heavy or light. We consider bino as the dominant component of dark matter candidate, and the observed dark matter relic density is achieved via the neutralino-stau coannihilations. Considering the Generalized Minimal Supergravity (GmSUGRA), we show …
This review provides an elementary discussion of electroweak symmetry breaking in the minimal and the next-to-minimal supersymmetric models with the focus on the fine-tuning problem -- the tension between natural electroweak symmetry breaking and the direct search limit on the Higgs boson mass. Two generic solutions of the fine-tuning problem are discussed in detail: models with unusual Higgs decays; and models with unusual pattern of soft supersymmetry breaking parameters.
We introduce in an arbitrary supersymmetric version of the standard model without elementary scalars a logarithmic operator which is irrelevant in the limit in which all symmetries are respected. However through a dynamical mechanism of the Nambu Jona Lasinio type this operator may produce two fermion vacuum condensates that may account for electroweak and contribute to supersymmetry breaking. Some of the phenomenological consequences of this set-up are discussed.
These lectures are a very brief introduction to low energy supersymmetry (SUSY). The approach to the construction of SUSY Lagrangians based on the superfield formalism is considered. The minimal supersymmetric standard model (MSSM) is specified. The breakdown of gauge symmetry and Higgs phenomenology within the simplest SUSY extensions of the standard model (SM) are briefly reviewed. The upper bound on the mass of the lightest Higgs boson and little hierarchy problem in SUSY models are discussed.
Mirage mediation realized in the Kachru-Kallosh-Linde-Trivedi (KKLT) flux compactification can naturally suppress the up-type Higgs soft mass at low energy scales. As a result, compared to the conventional scenarios, the degree of electroweak fine-tuning can be reduced further up to by a loop factor if the Higgsinos are much lighter than the heavy Higgs doublet. Interestingly, this feature holds even in high-scale supersymmetry as long as the gauge coupling unification, which is required as a prerequisite for mirage mediation, accommodates such light Higgsinos. Under the experimental constrain…
In the N=1 supersymmetric extension of the Standard Model, neutralinos associated in supermultiplets with the neutral electroweak gauge and Higgs bosons are, as well as gluinos, Majorana fermions. They can be paired with the Majorana fermions of novel gaugino/scalar supermultiplets, as suggested by extended N=2 supersymmetry, to Dirac particles. Matter fields are not extended beyond the standard N=1 supermultiplets in N=1/N=2 hybrid supersymmetry to preserve the chiral character of the theory. Complementing earlier analyses in the color sector, central elements of such an electroweak scenario …
We propose a hybrid mediation and hybrid supersymmetry breaking. In particular the RG-invariant anomaly mediation is considered. Together with additional gravity mediation the slepton tachyon problem of anomaly mediation is solved automatically. The special properties are that all of color sparticles masses fall into several TeV region due to the large $m_0$ and $m_{32}$ which are well beyond the scope of current LHC Run II limits. Unlike the gauge mediation, the dark matter candidate is still the lightest neutralino and the correct dark matter relic density can be realized within the framewor…
We demonstrate that electroweak baryogenesis can occur in a supersymmetric model with an exact R-symmetry. The minimal R-symmetric supersymmetric model contains chiral superfields in the adjoint representation, giving Dirac gaugino masses, and an additional set of "R-partner" Higgs superfields, giving R-symmetric μ-terms. New superpotential couplings between the adjoints and the Higgs fields can simultaneously increase the strength of the electroweak phase transition and provide additional tree-level contributions to the lightest Higgs mass. Notably, no light stop is present in this framework,…
The Fermi-Lab Collaboration has announced the results for the measurement of muon anomalous magnetic moment. Combining with the previous results by the BNL experiment, we have $4.2 σ$ deviation from the Standard Model (SM), which strongly implies the new physics around 1 TeV. To explain the muon anomalous magnetic moment naturally, we analyze the corresponding five Feynman diagrams in the Supersymetric SMs (SSMs), and show that the Electroweak Supersymmetry (EWSUSY) is definitely needed. We realize the EWSUSY in the Minimal SSM (MSSM) with Genernalized Mininal Supergravity (GmSUGRA). We find l…
We will explore the consequences on the electroweak breaking condition, the mass of supersymmetric partners and the scale at which supersymmetry is broken, for arbitrary values of the supersymmetric parameters tan(beta) and the stop mixing X_t, which follow from the Higgs discovery with a mass m_H\simeq 126 GeV at the LHC. Within the present uncertainty on the top quark mass we deduce that radiative breaking requires tan(beta) \gtrsim 7 for maximal mixing X_t\simeq \sqrt{6}, and tan(beta) \gtrsim 20 for small mixing X_t\lesssim 1. The scale at which supersymmetry is broken \mathcal M can be of…
The null results of the LHC searches have put strong bounds on new physics scenario such as supersymmetry (SUSY). With the latest values of top quark mass and strong coupling, we study the upper bounds on the sfermion masses in Split-SUSY from the observed Higgs boson mass and electroweak (EW) vacuum stability. To be consistent with the observed Higgs mass, we find that the largest value of supersymmetry breaking scales $M_{S}$ for $\tanβ=2$ and $\tanβ=4$ are $\mathcal{O} (10^{3}\, {\rm TeV})$ and $\mathcal{O} (10^{1.5}\, {\rm TeV})$ respectively, thus putting an upper bound on the sfermion ma…
The lack of evidence for the production of colored supersymmetric particles at the LHC has increased interest in searches for superpartners of the electroweak SM gauge bosons, namely the neutralinos and charginos. These are challenging due to the weak nature of the production process, and the existing discovery reach has significant gaps in due to the difficulty of separating the supersymmetric signal from SM diboson events that produce similar final states and kinematics. We apply the Recursive Jigsaw Reconstruction technique to study final states enriched in charged leptons and missing trans…
The observed Higgs boson mass poses a new puzzle in addition to the longstanding problem of the origin of the electroweak scale; the shallowness of the Higgs potential. The Higgs quartic coupling even seems to vanish at around the Planck scale within the uncertainties of the top quark mass and the strong gauge coupling. We show that the shallowness of the Higgs potential might be an outcome of supersymmetry breaking at around the Planck scale. There, the electroweak fine-tuning in the Higgs quadratic terms leads to an almost vanishing quartic coupling at around the Planck scale.
This paper discusses electroweak collider signatures of the NMSSM with multiple-sector gauge mediation. We focus on the production of neutralinos and charginos which cascade decay into standard model particles and lighter supersymmetric particles, with special emphasis on final states with multiple photons. A search strategy for signatures with at least three photons is presented and compared with current exclusion limits based on two-photon searches. We show that in many regions of the parameter space our strategy gives stronger constraints than the existing two-photon analysis for these mode…
Considering the Generalized Minimal Supergravity Model (GmSUGRA) in the Minimal Supersymmetric Standard Model (MSSM), we study the Electroweak Supersymmetry (EWSUSY), where the squarks and/or gluino are heavy around a few TeVs while the sleptons, sneutrinos, Bino, Winos, and/or Higgsinos are light within one TeV. We resolves the $(g_μ-2)/2$ discrepancy for the muon anomalous magnetic moment in the Standard Model (SM) successfully and identifies a parameter space where such solutions also have the electroweak fine-tuning measures $Δ_{EW}~16.5$ (6$\%$) and $Δ_{EW}~25$ (4$\%$) without and with th…
The observed Higgs boson mass and the naturalness argument leave us a narrow window for the soft mass spectrum in natural supersymmetry that can be studied through the electroweak precision tests (EWPTs). We divide the analysis into the Higgs sector constrained by the charged Higgs mass bound, the neutralino-chargino sector constrained by the chargino mass bound, and the third-generation squark sector tightly constrained by the observed Higgs mass. Total contributions to EWPTs in the MSSM and NMSSM are both presented. It turns out that natural MSSM is excluded at 68\% CL but consistent at 95\%…
Electroweak Precision Data and Gravitino Dark Matter
在目前的精确度水平上，电弱精密测量可以提供关于超对称性可能尺度的间接信息。我们回顾了目前的mSUGRA型模型的精密数据的灵敏度与引力子作为最轻的超对称粒子（LSP）。卡方拟合基于M_W、sin^2 θ_eff、（g-2）_mu、BR（b -> s γ）和最轻的MSSM希格斯玻色子质量M_h。我们发现了相对较轻的软超导体破碎质量的迹象，为LHC和ILC提供了良好的前景，在某些情况下也为Tevatron。
Recent LHC data, together with the electroweak naturalness argument, suggest that the top squarks may be significantly lighter than the other sfermions. We present supersymmetric models in which such a split spectrum is obtained through "geometries": being "close to" electroweak symmetry breaking implies being "away from" supersymmetry breaking, and vice versa. In particular, we present models in 5D warped spacetime, in which supersymmetry breaking and Higgs fields are located on the ultraviolet and infrared branes, respectively, and the top multiplets are localized to the infrared brane. The …
We show that the electroweak fine-tuning parameter Δ_{\rm EW} derived from the well-known electroweak symmetry breaking condition written in terms of weak scale parameters leads to {\it a bound on fine-tuning in the MSSM} and explain its utility for phenomenological analyses. We argue that a small magnitude of the mu parameter, and the concomitant presence of light higgsinos, is the most basic consequence of naturalness in SUSY models, and list the resulting implications of this for experiments at the LHC and at future e^+e^- colliders.
Extra vector-like matter with both electroweak-singlet masses and large Yukawa couplings can significantly raise the lightest Higgs boson mass in supersymmetry through radiative corrections. I consider models of this type that involve a large Yukawa coupling between weak isotriplet and isodoublet chiral supermultiplets. The particle content can be completed to provide perturbative gauge coupling unification, in several different ways. The impact on precision electroweak observables is shown to be acceptably small, even if the new particles are as light as the current experimental bounds of ord…
Models of natural supersymmetry seek to solve the little hierarchy problem by positing a spectrum of light higgsinos <~ 200-300 GeV and light top squarks <~ 600 GeV along with very heavy squarks and TeV-scale gluinos. Such models have low electroweak fine-tuning and satisfy the LHC constraints. However, in the context of the MSSM, they predict too low a value of m(h), are frequently in conflict with the measured b\to sγbranching fraction and the relic density of thermally produced higgsino-like WIMPs falls well below dark matter (DM) measurements. We propose "radiative natural SUSY" (RNS) whic…
The second period of datataking at the Large Hadron Collider (LHC) has provided a large dataset of proton-proton collisions that is unprecedented in terms of its centre-of-mass energy of 13 TeV and integrated luminosity of almost 140 fb$^{-1}$. These data constitute a formidable laboratory for the search for new particles predicted by models of supersymmetry. The analysis activity is still ongoing, but a host of results on supersymmetry has already been released by the general purpose LHC experiments ATLAS and CMS. In this paper, we provide a map into this remarkable body of research, which sp…
Sparticle Spectroscopy and Electroweak Symmetry Breaking with Gauge-Mediated Supersymmetry Breaking
介绍了规范介导的超对称破缺现象。对极小模型进行了重整化群分析，其中施加了辐射电弱对称性破缺的约束。由此产生的超伴子和希格斯玻色子的光谱是高度相关的，只依赖于几个参数。超伙伴质量比和总和规则确定，可以在未来的对撞机进行测试。其中一些关系在数学上对信使尺度敏感，而另一些关系则允许规范调解与其他传输超对称性破缺的方案区分开来。偏离极小模型，例如较大的信使表示和对希格斯扇区质量的额外贡献，在某些情况下可以显着修改低能谱。这些修正包括用一个斯莱普顿或希格斯诺作为最轻的标准模型超伴子，或者标量和高吉诺之间的奇异质量关系。对$b \to s γ$的贡献和由此产生的超伙伴质量上的束缚也为极小模型。最后，独特的对撞机签名的重带电粒子的生产，或衰变到Goldstino内的检测器进行了讨论。
