Gaugino Masses Research Articles

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.

Nonuniversal gaugino masses in a magnetized toroidal compactification of SYM theories

This paper proposes a concrete model of nonuniversal gaugino masses on the basis of higher-dimensional supersymmetric Yang-Mills theories compactified on a magnetized factorizable torus, and we estimate the gauge coupling constants and gaugino masses in the model. In the magnetized toroidal compactifications, the four-dimensional effective action can be obtained analytically identifying its dependence on moduli fields, where the magnetic fluxes are able to yield the flavor structure of the minimal supersymmetric standard model (MSSM). The obtained gauge kinetic functions contains multi moduli fields and their dependence is nonuniversal for the three gauge fields. The nonuniversal gauge kinetic functions can lead to nonuniversal gaugino masses at a certain high energy scale (e.g. compactification scale). Our numerical analysis of them shows that, particular ratios of gaugino masses, which were found to enhance the Higgs boson mass and lead to “natural supersymmetry” in the MSSM, can be realized in our model, while the gauge couplings are unified as is achieved in the MSSM.

Neutralino dark matter and other LHC predictions from quasi Yukawa unification

We explore the dark matter and LHC implications of t−b−τ quasi Yukawa unification in the framework of supersymmetric models based on the gauge symmetry G=SU(4)c×SU(2)L×SU(2)R. The deviation from exact Yukawa unification is quantified by a dimensionless parameter C (|C|≲0.2), such that the Yukawa couplings at MGUT are related by yt:yb:yτ=|1+C|:|1−C|:|1+3C|. In contrast to earlier studies which focused on universal gaugino masses, we consider non-universal gaugino masses at MGUT that are compatible with the gauge symmetry G. Our results reveal a variety of neutralino dark matter scenarios consistent with the observations. These include stau and chargino coannihilation scenarios, the A-resonance scenario, as well as Higgsino dark matter solutions which are more readily probed by direct detection searches. The gluino mass is found to be ≲4 TeV, the stop mass is ≳2 TeV, while the first two family squarks and sleptons are of order 4–5 TeV and 3 TeV respectively.

Phenomenological aspects of no-scale inflation models

We discuss phenomenological aspects of inflationary models wiith a no-scale supergravity Kähler potential motivated by compactified string models, in which the inflaton may be identified either as a Kähler modulus or an untwisted matter field, focusing on models that make predictions for the scalar spectral index ns and the tensor-to-scalar ratio r that are similar to the Starobinsky model. We discuss possible patterns of soft supersymmetry breaking, exhibiting examples of the pure no-scale type m0 = B0 = A0 = 0, of the CMSSM type with universal A0 and m0 ≠ 0 at a high scale, and of the mSUGRA type with A0 = B0 + m0 boundary conditions at the high input scale. These may be combined with a non-trivial gauge kinetic function that generates gaugino masses m1/2 ≠ 0, or one may have a pure gravity mediation scenario where trilinear terms and gaugino masses are generated through anomalies. We also discuss inflaton decays and reheating, showing possible decay channels for the inflaton when it is either an untwisted matter field or a Kähler modulus. Reheating is very efficient if a matter field inflaton is directly coupled to MSSM fields, and both candidates lead to sufficient reheating in the presence of a non-trivial gauge kinetic function.

Indirect and direct detection prospect for TeV dark matter in the nine parameter MSSM

We investigate the prospects of indirect and direct dark matter searches within the minimal supersymmetric standard model with nine parameters (MSSM-9). These nine parameters include three gaugino masses, Higgs, slepton and squark masses, all treated independently. We perform a Bayesian Monte Carlo scan of the parameter space taking into consideration all available particle physics constraints such as the Higgs mass of 126 GeV, upper limits on the scattering cross section from direct-detection experiments, and assuming that the MSSM-9 provides all the dark matter abundance through a thermal freeze-out mechanism. Within this framework we find the two most probable regions for dark matter: 1-TeV Higgsino-like and 3-TeV Wino-like neutralinos. We discuss prospects for future indirect [in particular the Cherenkov Telescope Array (CTA)] and direct detection experiments. We find that for slightly contracted dark matter profiles in our Galaxy, which can be caused by the effects of baryonic infall in the Galactic center, CTA will be able to probe a large fraction of the remaining allowed region in synergy with future direct detection experiments like XENON-1T.

Distinguishing LSP archetypes via gluino pair production at LHC13

The search for supersymmetry at Run 1 of LHC has resulted in gluino mass limits m(gluino)>~ 1.3 TeV for the case where m(gluino)<<m(squark) and in models with gaugino mass unification. The increased energy and ultimately luminosity of LHC13 will explore the range m(gluino)~ 1.3-2 TeV. We examine how the discovery of SUSY via gluino pair production would unfold via a comparative analysis of three LSP archetype scenarios: 1. mSUGRA/CMSSM model with a bino-like LSP, 2. charged SUSY breaking (CSB) with a wino-like LSP and 3. SUSY with radiatively-driven naturalness (RNS) and a higgsino-like LSP. In all three cases we expect heavy-to-very-heavy squarks as suggested by a decoupling solution to the SUSY flavor and CP problems and by the gravitino problem. For all cases, initial SUSY discovery would likely occur in the multi-b-jet + ETMISS channel. The CSB scenario would be revealed by the presence of highly-ionizing, terminating tracks from quasi-stable charginos. As further data accrue, the RNS scenario with 100-200 GeV higgsino-like LSPs would be revealed by the build-up of a mass edge/bump in the OS/SF dilepton invariant mass which is bounded by the neutralino mass difference. The mSUGRA/CMSSM archetype would contain neither of these features but would be revealed by a buildup of the usual multi-lepton cascade decay signatures.

Light Higgsino dark matter in the MSSM on D-branes

When supersymmetry (SUSY) breaking is dominated by the complex structure moduli and the universal dilaton, a subset of the SUSY parameter space in a realistic minimal supersymmetric standard model constructed from intersecting/magnetized D-branes are universal, similar to the effective minimal supergravity (mSUGRA)/constrained minimal supersymmetric standard model (CMSSM) parameter space with a universal scalar mass m0, a universal gaugino mass and with the universal trilinear term fixed to be minus the gaugino mass, A0 = −m1/2. More generally, the scalar mass-squared terms for sfermions are split about the Higgs mass-squared terms, and , for generic values of the Kähler moduli. The scalar masses are universal only for a specific choice of the Kähler moduli. The hyperbolic branch/focus point (HB/FP) regions of this parameter space are present for both and . Interestingly, it is known that FPs may be realized with any boundary condition of the form with x an arbitrary constant, the same form as those in this model. Thus, we should expect to obtain the same set of FPs in the model regardless of the choice of Kähler moduli. It should be emphasized that the more general choice of Kähler moduli goes beyond (mSUGRA/CMSSM). It is shown that there exists superpartner spectra with a light Higgsino-like LSP with 230–350 GeV and a Higgs mass in the range 124–126 GeV, and which satisfy most standard experimental constraints. Consequently, viable spectra with low electroweak fine-tuning between 3%–7% may be obtained. The spin-independent direct-detection crosssections are in range of future experiments such as XENON−1 T and super CDMS, while the relic density is smaller than the WMAP and Planck bounds by roughly a factor of ten, implying that the LSP is sub-dominant component of dark matter. In addition, most of the spectra are consistent with constraints from indirect-detection experiments.

Nonstandard supersymmetry breaking and Dirac gaugino masses without supersoftness

I consider models in which non-standard supersymmetry breaking terms, including Dirac gaugino masses, arise from F-term breaking mediated by operators with a $1/M^3$ suppression. In these models, the supersoft properties found in the case of D-term breaking are absent in general, but can be obtained as a special case that is a fixed point of the renormalization group equations. The $\mu$ term is replaced by three distinct supersymmetry-breaking parameters, decoupling the Higgs scalar potential from the Higgsino masses. Both holomorphic and non-holomorphic scalar cubic interactions with minimal flavor violation are induced in the supersymmetric Standard Model Lagrangian.

Hiding the little hierarchy problem in the NMSSM

In this paper we consider a set of soft supersymmetry breaking terms within the NMSSM which leads to a small hierarchy between the supersymmetry breaking scale and the electroweak scale. Specifically only the gaugino masses and the soft term in the Higgs sector are non-vanishing at the GUT scale. This pattern can be found in gaugino mediated models and in higher-dimensional orbifold GUTs. We study the phenomenology of this scenario and find different low energy spectra depending on the Yukawa coupling $\lambda$ of the NMSSM singlet. In particular, for low values of $\lambda$ the singlet is the lightest scalar and the singlino is the LSP while for large values of $\lambda$ both are heavy and the gravitino can be the LSP. The singlet pseudoscalar is very light in the entire parameter space.

Seminatural SUSY from theE7nonlinear sigma model

We present a new focus point supersymemtry breaking scenario based on the supersymmetric $E_7$ non-linear sigma model. In this non-linear sigma model, squarks and sleptons are identified with (pseudo) Nambu-Goldstone bosons. Their masses are generated only radiatively through gauge and yukawa interactions, and they are much smaller than the gravitino and gaugino masses at a high energy scale. On the other hand, Higgs doublets belong to matter multiplets and hence may have unsuppressed supersymmetry-breaking soft masses. We consider their masses to be equal to the gravitino mass at the high energy scale, assuming the minimal Kahler potential for Higgs doublets. We show that the fine-tuning measure of the electroweak symmetry breaking scale is reduced significantly to $\Delta=30-70$, if the ratio of the gravitino mass to the gaugino mass is around $5/4$. Also, the prospects of the discovery/exclusion of supersymmetric particles at the Large Hadron Collider and dark matter direct detection experiments are discussed.

LHC phenomenology of natural MSSM with non-universal gaugino masses at the unification scale

In this letter, we study collider phenomenology in the supersymmetric Standard Model with a certain type of non-universal gaugino masses at the gauge coupling unification scale, motivated by the little hierarchy problem. In this scenario, especially the wino mass is relatively large compared to the gluino mass at the unification scale, and the heavy wino can relax the fine-tuning of the higgsino mass parameter, so-called $\mu$-parameter. Besides, it will enhance the lightest Higgs boson mass due to the relatively large left-right mixing of top squarks through the renormalization group (RG) effect. Then $125$ GeV Higgs boson could be accomplished, even if the top squarks are lighter than $1$ TeV and the $\mu$ parameter is within a few hundreds GeV. The right-handed top squark tends to be lighter than the other sfermions due to the RG runnings, then we focus on the top squark search at the LHC. Since the top squark is almost right-handed and the higgsinos are nearly degenerate, $2b + E_T^{\rm miss}$ channel is the most sensitive to this scenario. We figure out current and expected experimental bounds on the lightest top squark mass and model parameters at the gauge coupling unification scale.

Shifted focus point of the Higgs mass parameter from the minimal mixed mediation of supersymmetry breaking

We employ both the minimal gravity- and the minimal gauge mediations of supersymmetry breaking at the grand unified theory (GUT) scale in a single supergravity framework, assuming the gaugino masses are generated dominantly by the minimal gauge mediation effects. In such a "minimal mixed mediation model," a "focus point" of the soft Higgs mass parameter, m_{h_u}^2 emerges at 3-4 TeV energy scale, which is exactly the stop mass scale needed for explaining the 126 GeV Higgs boson mass without the "A-term" at the three loop level. As a result, m_{h_u}^2 can be quite insensitive to various trial stop masses at low energy, reducing the fine-tuning measures to be much smaller than 100 even for a 3-4 TeV low energy stop mass and -0.5 < A_t/m_0 < +0.1 at the GUT scale. The gluino mass is predicted to be about 1.7 TeV, which could readily be tested at LHC run2.

Supernatural MSSM

We point out that the electroweak fine-tuning problem in the supersymmetric Standard Models (SSMs) is mainly due to the high energy definition of the fine-tuning measure. We propose super-natural supersymmetry which has an order one high energy fine-tuning measure automatically. The key point is that all the mass parameters in the SSMs arise from a single supersymmetry breaking parameter. In this paper, we show that there is no supersymmetry electroweak fine-tuning problem explicitly in the Minimal SSM (MSSM) with no-scale supergravity and Giudice-Masiero (GM) mechanism. We demonstrate that the $Z$-boson mass, the supersymmteric Higgs mixing parameter $\mu$ at the unification scale, and the sparticle spectrum can be given as functions of the universal gaugino mass $M_{1/2}$. Because the light stau is the lightest supersymmetric particle (LSP) in the no-scale MSSM, to preserve $R$ parity, we introduce a non-thermally generated axino as the LSP dark matter candidate. We estimate the lifetime of the light stau by calculating its 2-body and 3-body decays to the LSP axino for several values of axion decay constant $f_a$, and find that the light stau has a lifetime $\tau_{\tilde \tau_1}$ in $[10^{-4},100]$ s for an $f_a$ range $[10^{9},10^{12}]$ GeV. We show that our next to the LSP stau solutions are consistent with all the current experimental constraints, including the sparticle mass bounds, B-physics bounds, Higgs mass, cosmological bounds, and the bounds on long-lived charge particles at the LHC.

Non-universal gaugino mass models under the lamppost of muon (g-2)

In unified $\mathcal{N}=1$ supergravity scenario the gaugino masses can be non-universal. The patterns of these non-universalities are dictated by the vacuum expectation values of non-singlet chiral super-fields in visible sector. Here, we have analysed the model independent correlations among the gaugino masses with an aim to explain the $[1\div 3]\sigma$ excess of muon (g-2) ($\Delta a_\mu$). We have also encapsulated the interconnections among other low and high scale parameters, compatible with the collider constraints, Higgs mass, relic density and flavour data. We have noted that the existing non-universal models are not capable enough to explain $\Delta a_\mu$ at $[1\div 2]\sigma$ level. In the process, we have also shown the impact of recent limits from the searches for disappearing track and long lived charged particles at the LHC. These are the most stringent limits so far ruling out a large parameter space allowed by other constraints. We have also performed model guided analysis where gaugino masses are linear combination of contributions coming from singlet and non-singlet chiral super-fields. Here, a new mixing parameter has been introduced. Following the earlier methodology, we have been able to constrain this mixing parameter and pin down the promising models on this notion.

New calculations in Dirac gaugino models: operators, expansions, and effects

In this work we calculate important one loop SUSY-breaking parameters in models with Dirac gauginos, which are implied by the existence of heavy messenger fields. We find that these SUSY-breaking effects are all related by a small number of parameters, thus the general theory is tightly predictive. In order to make the most accurate analyses of one loop effects, we introduce calculations using an expansion in SUSY breaking messenger mass, rather than relying on postulating the forms of effective operators. We use this expansion to calculate one loop contributions to gaugino masses, non-holomorphic SM adjoint masses, new A-like and B-like terms, and linear terms. We also test the Higgs potential in such models, and calculate one loop contributions to the Higgs mass in certain limits of R-symmetric models, finding a very large contribution in many regions of the , where Higgs fields couple to standard model adjoint fields.

CP-safe gravity mediation and muong − 2

We propose a CP-safe gravity mediation model, where the phases of the Higgs B parameter, scalar trilinear couplings and gaugino mass parameters are all aligned. Since all dangerous CP violating phases are suppressed, we are now safe to consider low-energy SUSY scenarios. As an application, we consider a gravity mediation model explaining the observed muon $g-2$ anomaly. The CP-safe property originates in two simple assumptions: SUSY breaking in the K\"ahler potential and a shift symmetry of a SUSY breaking field $Z$. As a result of the shift symmetry, the imaginary part of $Z$ behaves as a QCD axion, leading to an intriguing possibility: the strong CP problem in QCD and the SUSY CP problem are solved simultaneously.

Invisible decays of the heavier Higgs boson in the minimal supersymmetric standard model

We consider the possibility that the heavier CP-even Higgs boson~($H^0$) in the minimal supersymmetric standard model (MSSM) decays invisibly into neutralinos in the light of the recent discovery of the 126 GeV resonance at the CERN Large Hadron Collider (LHC). For this purpose we consider the minimal supersymmetric standard model with universal, non-universal and arbitrary boundary conditions on the supersymmetry breaking gaugino mass parameters at the grand unified scale. Typically, scenarios with universal and nonuniversal gaugino masses do not allow invisible decays of the lightest Higgs boson~($h^0$), which is identified with the $126$ GeV resonance, into the lightest neutralinos in the MSSM. With arbitrary gaugino masses at the grand unified scale such an invisible decay is possible. The second lightest Higgs boson can decay into various invisible final states for a considerable region of the MSSM parameter space with arbitrary gaugino masses as well as with the gaugino masses restricted by universal and nonuniversal boundary conditions at the grand unified scale.The possibility of the second lightest Higgs boson of the MSSM decaying into invisible channels is more likely for arbitrary gaugino masses at the grand unified scale. The heavier Higgs boson decay into lighter particles leads to the intriguing possibility that the entire Higgs boson spectrum of the MSSM may be visible at the LHC even if it decays invisibly, during the searches for an extended Higgs boson sector at the LHC. In such a scenario the nonobservation of the extended Higgs sector of the MSSM may carefully be used to rule out regions of the MSSM parameter space at the LHC.

The hierarchy solution to the LHC inverse problem

Supersymmetric (SUSY) models, even those described by relatively few parameters, generically allow many possible SUSY particle (sparticle) mass hierarchies. As the sparticle mass hierarchy determines, to a great extent, the collider phenomenology of a model, the enumeration of these hierarchies is of the utmost importance. We therefore provide a readily generalizable procedure for determining the number of sparticle mass hierarchies in a given SUSY model. As an application, we analyze the gravity-mediated SUSY breaking scenario with various combinations of GUT-scale boundary conditions involving different levels of universality among the gaugino and scalar masses. For each of the eight considered models, we provide the complete list of forbidden hierarchies in a compact form. Our main result is that the complete (typically rather large) set of forbidden hierarchies among the eight sparticles considered in this analysis can be fully specified by just a few forbidden relations involving much smaller subsets of sparticles.

CP-odd component of the lightest neutral Higgs boson in the MSSM

The Higgs sector of the Minimal Supersymmetric Extension of the Standard Model may be described with a two Higgs doublet model with properties that depend on the soft supersymmetry breaking parameters. For instance, flavor independent CP-violating phases associated with the gaugino masses, the squark trilinear mass parameters and the Higgsino mass parameter $\mu$ may lead to sizable CP-violation in the Higgs sector. For these CP-violating effects to affect the properties of the recently observed SM-like Higgs resonance, the non-standard charged and neutral Higgs bosons masses must be of the order of the weak scale, and both $\mu$ as well as the trilinear stop mass parameter $A_t$ must be of the order or larger than the stop mass parameters. Constraints on this possibility come from direct searches for non-standard Higgs bosons, precision measurements on the lightest neutral Higgs properties, including its mass, and electric dipole moments. In this article, we discuss these constraints within the MSSM, trying to evaluate the possible size of the CP-odd component of the lightest neutral Higgs boson, and the possible experimental tests of this CP-violating effect at the LHC.

GUT-inspired supersymmetric model forh→γγand the muong−2

We study a GUT-inspired supersymmetric model with non-universal gaugino masses that can explain the observed muon g-2 anomaly while simultaneously accommodating an enhancement or suppression in the h \rightarrow\gamma\gamma decay channel. In order to accommodate these observations and m_h \simeq 125-126 GeV, the model requires a spectrum consisting of relatively light sleptons whereas the colored sparticles are heavy. The predicted stau mass range corresponding to R_{\gamma \gamma}\ge 1.1 is 100 {\rm \ GeV} \lesssim m_{\tilde{\tau}} \lesssim 200 {\rm \ GeV}. The constraint on the slepton masses, particularly on the smuons, arising from considerations of muon g-2 is somewhat milder. The slepton masses in this case are predicted to lie in the few hundred GeV range. The colored sparticles turn out to be considerably heavier with m_{\tilde{g}} \gtrsim 4.5 {\rm \ TeV} and m_{\tilde{t}_1} \gtrsim 3.5 {\rm \ TeV}, which makes it challenging for these to be observed at the 14 TeV LHC.