Dirac Gaugino Masses Research Articles

Color-octet scalars in Dirac gaugino models with broken R symmetry

In this work we study the collider phenomenology of color-octet scalars (sgluons) in supersymmetric models with Dirac gaugino masses that feature an explicitly broken R symmetry (R-broken models). We construct such models by augmenting minimal R-symmetric models with a fairly general set of supersymmetric and softly supersymmetry-breaking operators that explicitly break R symmetry. We then compute the rates of all significant two-body decays and highlight new features that appear as a result of R symmetry breaking, including enhancements to extant decay rates, novel tree- and loop-level decays, and improved cross sections of single sgluon production. We demonstrate in some detail how the familiar results from minimal R-symmetric models can be obtained by restoring R symmetry. In parallel to this discussion, we explore constraints on these models from the Large Hadron Collider. We find that, in general, R symmetry breaking quantitatively affects existing limits on color-octet scalars, perhaps closing loopholes for light CP-odd (pseudoscalar) sgluons while opening one for a light CP-even (scalar) particle. Qualitatively, however, we find that — much as for minimal R-symmetric models, despite stark differences in phenomenology — scenarios with broken R symmetry and two sgluons below the TeV scale can be accommodated by existing searches.

Leading two-loop corrections to the Higgs boson masses in SUSY models with Dirac gauginos

We compute the two-loop O(as*at) corrections to the Higgs boson masses in supersymmetric extensions of the Standard Model with Dirac gaugino masses. We rely on the effective-potential technique, allow for both Dirac and Majorana mass terms for the gluinos, and compute the corrections in both the DRbar and on-shell renormalisation schemes. We give detailed results for the MDGSSM and the MRSSM, and simple approximate formulae valid in the decoupling limit for all currently-studied variants of supersymmetric models with Dirac gluinos. These results represent the first explicit two-loop calculation of Higgs boson masses in supersymmetric models beyond the MSSM and the NMSSM.

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.

Exploring New Models in All Detail withSARAH

I give an overview about the features theMathematicapackageSARAHprovides to study new models. In general,SARAHcan handle a wide range of models beyond the MSSM coming with additional chiral superfields, extra gauge groups, or distinctive features like Dirac gaugino masses. All of these models can be implemented in a compact form inSARAHand are easy to use:SARAHextracts all analytical properties of the given model like two-loop renormalization group equations, tadpole equations, mass matrices, and vertices. Also one- and two-loop corrections to tadpoles and self-energies can be obtained. For numerical calculationsSARAHcan be interfaced with other tools to get the mass spectrum, to check flavour or dark matter constraints, and to test the vacuum stability or to perform collider studies. In particular, the interface toSPhenoallows a precise prediction of the Higgs mass in a given model comparable to MSSM precision by incorporating the important two-loop corrections. I show in great detail with the example of theB-L-SSM howSARAHtogether withSPheno,HiggsBounds/HiggsSignals,FlavorKit,Vevacious,CalcHep,MicrOmegas,WHIZARD, andMadGraphcan be used to study all phenomenological aspects of a model.

Dirac gauginos in low scale supersymmetry breaking

It has been claimed that Dirac gaugino masses are necessary for realistic models of low-scale supersymmetry breaking, and yet very little attention has been paid to the phenomenology of a light gravitino when gauginos have Dirac masses. We begin to address this deficit by investigating the couplings and phenomenology of the gravitino in the effective Lagrangian approach. We pay particular attention to the phenomenology of the scalar octets, where new decay channels open up. This leads us to propose a new simplified effective scenario including only light gluinos, sgluons and gravitinos, allowing the squarks to be heavy – with the possible exception of the third generation. Finally, we comment on the application of our results to Fake Split Supersymmetry.

Constrained minimal Dirac gaugino supersymmetric standard model

We examine the possibilities for constructing models with Dirac gaugino masses and unification of gauge couplings. We identify one promising model, and discuss to what extent it can have a "natural SUSY" spectrum. We then determine the low-energy constraints upon it, and propose a constrained set of boundary conditions at the unification scale. We describe the implementation of these boundary conditions in the spectrum-generator generator \SARAH and we perform a first exploration of the parameter space, specifically searching for points where the spectrum is relatively light. It is shown that the pattern of the masses of SUSY states is very different compared to any expectations from the constrained MSSM.

Mapping Dirac gaugino masses

We investigate the mapping of Dirac gaugino masses through regions of strong coupling, focussing on SQCD with an adjoint. These models have a well-known Kutasov duality, under which a weakly coupled electric UV description can flow to a different weakly coupled magnetic IR description. We provide evidence to show that Dirac gaugino mass terms map as lim_{mu->infty} mD/(g kappa^{1/(k+1}} = lim_{mu->0} tilde{mD}/(tilde{g} tilde{kappa}^{1/(k+1}} under such a flow, where the coupling kappa appears in the superpotential of the canonically normalised theory as W \supset kappa X^{k+1}. This combination is an RG-invariant to all orders in perturbation theory, but establishing the mapping in its entirety is not straightforward because Dirac masses are not the spurions of holomorphic couplings in the N=1 theory. To circumvent this, we first demonstrate that deforming the Kutasov theory can make it flow to an N=2 theory with parametrically small N=1 deformations. Using harmonic superspace techniques we then show that the N=1 deformations can be recovered from electric and magnetic FI-terms that break N=2 -> N=1, and also show that pure Dirac mass terms can be induced by the same mechanism. We then find that the proposed RG-invariant is indeed preserved under N=2 duality, and thence along the flow to the dual N=1 Kutasov theories. Possible phenomenological applications are discussed.

Dirac gauginos and the 125 GeV Higgs

Abstract We investigate the mass, production and branching ratios of a 125 GeV Higgs in models with Dirac gaugino masses. We give a discussion of naturalness, and describe how deviations from the Standard Model in the key Higgs search channels can be simply obtained. We then perform parameter scans using a SARAH package upgrade, which produces SPheno code that calculates all relevant quantities, including electroweak precision and flavour constraint data, to a level of accuracy previously impossible for this class of models. We study three different variations on the minimal Dirac gaugino extension of the (N)MSSM.

Electroweak baryogenesis inR-symmetric supersymmetry

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 \mu-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, and in fact, we require both stops to be above a few TeV to provide sufficient radiative corrections to the lightest Higgs mass to bring it up to 125 GeV. Large CP-violating phases in the gaugino/higgsino sector allow us to match the baryon asymmetry of the Universe with no constraints from electric dipole moments due to R-symmetry. We briefly discuss some of the more interesting phenomenology, particularly of the of the lightest CP-odd scalar.

Two-loop RGEs with Dirac gaugino masses

Abstract The set of renormalisation group equations to two-loop order for general supersymmetric theories broken by soft and supersoft operators is completed. As an example, the explicit expressions for the RGEs in a Dirac gaugino extension of the (N)MSSM are presented.

Exploring holographic general gauge mediation

We study models of gauge mediation with strongly coupled hidden sectors, employing a hard wall background as an holographic dual description. The structure of the soft spectrum depends crucially on the boundary conditions one imposes on bulk fields at the IR wall. Generically, vector and fermion correlators have poles at zero momentum, leading to gauge mediation by massive vector messengers and/or generating Dirac gaugino masses. Instead, non-generic choices of boundary conditions let one cover all of GGM parameter space. Enriching the background with R-symmetry breaking scalars, the SSM soft term structure becomes more constrained and similar to previously studied top-down models, while retaining the more analytic control the present bottom-up approach offers.

Supersoft supersymmetry is super-safe

We show that supersymmetric models with a large Dirac gluino mass can evade much of the jets plus missing energy searches at the LHC. Dirac gaugino masses arise from ``supersoft'' operators that lead to finite one-loop suppressed contributions to the scalar masses. A little hierarchy between the Dirac gluino mass 5--10 times heavier than the squark masses is automatic and technically natural, in stark contrast to supersymmetric models with Majorana gaugino masses. At the LHC, colored sparticle production is suppressed not only by the absence of gluino pair (or associated) production, but also because several of the largest squark pair production channels are suppressed or absent. We recast the null results from the present jets plus missing energy searches at the LHC for supersymmetry onto a supersoft supersymmetric simplified model. Assuming a massless lightest supersymmetric particle, we find the strongest bounds are as follows: 748 GeV from a $2j+{\mathrm{E\ensuremath{\llap{\not\;}}}}_{T}$ search at ATLAS ($4.7\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$) and 684 GeV from a combined jets plus missing energy search using ${\ensuremath{\alpha}}_{T}$ at CMS ($1.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$). In the absence of a future observation, we estimate the bounds on the squark masses to improve only modestly with increased luminosity. We also briefly consider the further weakening in the bounds as the lightest supersymmetric particle mass is increased.

Viable gravity-mediated supersymmetry breaking

We present a complete, viable model of gravity-mediated supersymmetry breaking that is safe from all flavor constraints. The central new idea is to employ a supersymmetry breaking sector without singlets, but with D-terms comparable to F-terms, causing supersymmetry breaking to be dominantly communicated through U(1)_R-symmetric operators. We construct a visible sector that is an extension of the MSSM where an \emph{accidental} U(1)_R symmetry emerges naturally. Gauginos acquire Dirac masses from gravity-mediated D-terms, and tiny Majorana masses from anomaly-mediated contributions. Contributions to soft breaking scalar (mass)^2 arise from flavor-arbitrary gravity-induced F-terms plus one-loop finite flavor-blind contributions from Dirac gaugino masses. Renormalization group evolution of the gluino causes it to naturally increase nearly an order of magnitude larger than the squark masses. This hierarchy, combined with an accidentially U(1)_R-symmetric visible sector, nearly eliminates all flavor violation constraints on the model. If we also freely tune couplings and phases within the modest range 0.1-1, while maintaining nearly flavor-anarchic Planck-suppression contributions, we find our model to be safe from Delta m_K, epsilon_K, and mu -> e lepton flavor violation. Dangerous U(1)_R-violating K\"ahler operators in the Higgs sector are eliminated through a new gauged U(1)_X symmetry that is spontaneously broken with electroweak symmetry breaking. Kinetic mixing between U(1)_X and U(1)_Y is present with loop-suppressed (but log-enhanced) size epsilon. The Z' associated with this U(1)_X has very peculiar couplings -- it has order one strength to Higgs doublets and approximately epsilon strength to hypercharge. The Z' could be remarkably light and yet have escaped direct and indirect detection.

Dirac gauginos and kinetic mixing

We present formulae for the calculation of Dirac gaugino masses at leading order in the supersymmetry breaking scale using the methods of analytic continuation in superspace and demonstrate a link with kinetic mixing, even for non-abelian gauginos. We illustrate the result through examples in field and string theory. We discuss the possibility that the singlet superfield that gives the U ( 1 ) gaugino a Dirac mass may be a modulus, and some consequences of the D-term coupling to the scalar component. We give examples of possible effects in colliders and astroparticle experiments if the modulus scalar constitutes decaying dark matter.

Dark matter with Dirac and Majorana gaugino masses

We consider the minimal supersymmetric extension of the Standard Model allowing both Dirac and Majorana gauginos. The Dirac masses are obtained by pairing up extra chiral multiplets: a singlet S for U(1)Y, a triplet T for SU(2)w and an octet Og for SU(3)c with the respective gauginos. The electroweak symmetry breaking sector is modified by the couplings of the new fields S and T to the Higgs doublets. We discuss two limits: i) both the adjoint scalars are decoupled with the main effect being the modification of the Higgs quartic coupling; ii) the singlet remaining light, and due to its direct coupling to sfermions, providing a new contribution to the soft masses and inducing new decay/production channels. We discuss the LSP in this scenario; after mentioning the possibility that it may be a Dirac gravitino, we focus on the case where it is identified with the lightest neutralino, and exhibit particular values of the parameter space where the relic density is in agreement with WMAP data. This is illustrated for different scenarios where the LSP is either a bino (in which case it can be a Dirac fermion) or bino-higgsino/wino mixtures. We also point out in each case the peculiarity of the model with respect to dark matter detection experiments.

Supersymmetry with a chargino NLSP and gravitino LSP

We demonstrate that the lightest chargino can be lighter than the lightest neutralino in supersymmetric models with Dirac gaugino masses as well as within a curious parameter region of the MSSM. Given also a light gravitino, such as from low scale supersymmetry breaking, this mass hierarchy leads to an unusual signal where every superpartner cascades down to a chargino that decays into an on-shell W and a gravitino, possibly with a macroscopic chargino track. We clearly identify the region of parameters where this signal can occur. We find it is generic in the context of the R-symmetric supersymmetric standard model, whereas it essentially only occurs in the MSSM when sign(M1) ≠ sign(M2) = sign(μ) and tan β is small. We briefly comment on the search strategies for this signal at the LHC.

Flavor in supersymmetry with an extendedRsymmetry

We propose a new solution to the supersymmetric flavor problem without flavor-blind mediation. Our proposal is to enforce a continuous or a suitably large discrete R-symmetry on weak scale supersymmetry, so that Majorana gaugino masses, trilinear A terms, and the μ term are forbidden. We find that replacing the minimal supersymmetric standard model with an R-symmetric supersymmetric model allows order one flavor-violating soft masses, even for squarks of order a few hundred GeV. The minimal R-symmetric supersymmetric model contains Dirac gaugino masses and R-symmetric Higgsino masses with no left-right mixing in the squark or slepton sector. Dirac gaugino masses of order a few TeV with vanishing A terms solve most flavor problems, while the R-symmetric Higgs sector becomes important at large tanβ. ∈ K can be accommodated if CP is preserved in the SUSY breaking sector, or if there is a moderate flavor degeneracy, which can arise naturally. ∈'/∈, as well as neutron and electron electric dipole moments, are easily within experimental bounds. The most striking phenomenological distinction of this model is the order one flavor violation in the squark and slepton sector, while the Dirac gaugino masses tend to be significantly heavier than the corresponding squark and slepton masses.