SUSY Breaking Terms Research Articles

A unified approach to supersymmetry breaking

General formulae for the soft SUSY breaking terms, valid in any SUGRA context, were derived in the mid-nineties. Since SUSY is not expected to have quantum anomalies, they should be valid in the quantum theory and be RG invariant down to the soft SUSY breaking scale. This observation enables us to give a uniform treatment of all phenomenological models for SUSY breaking and transmission, such as AMSB, GMSB, etc. In particular we find that the much discussed RG invariant formulae for soft SUSY breaking parameters in AMSB, effectively depend on a strong assumption of factorizability of the matter Kaehler metric. We then argue that there is no necessity for having ad hoc constructions such as mAMSB to counteract the negative squared slepton mass problem, since the natural framework that emerges in a sequestered model is one in which gaugino masses are as in AMSB, and the other soft terms are generated by RG running as in gaugino mediation.

Higgs Bosons Near 125 GeV in the NMSSM with Constraints at the GUT Scale

We study the NMSSM with universal Susy breaking terms (besides the Higgs sector) at the GUT scale. Within this constrained parameter space, it is not difficult to find a Higgs boson with a mass of about 125 GeV and an enhanced cross-section in the diphoton channel. An additional lighter Higgs boson with reduced couplings and a mass≲123 GeV is potentially observable at the LHC. The NMSSM-specific Yukawa couplingsλandκare relatively large and tanβis small, such thatλ,κ, and the top Yukawa coupling are of𝒪(1)at the GUT scale. The lightest stop can be as light as 105 GeV, and the fine-tuning is modest. WMAP constraints can be satisfied by a dominantly Higgsino-like LSP with substantial bino, wino, and singlino admixtures and a mass of~60–90 GeV, which would potentially be detectable by XENON100.

Hard and soft supersymmetry breaking for ‘graphinos’ in uniform magnetic fields

Using irreducible and reducible representations of the Dirac matrices, we study the two- and four-component quantum mechanical supersymmetric (SUSY) theories for ultrarelativistic fermions in (2 + 1) dimensions (‘graphinos’) in a background uniform magnetic field perpendicular to their plane of motion. We then consider ordinary and parity-violating mass terms and identify the former as a soft SUSY breaking term and the latter as the hard SUSY breaking one.

Brane-Higgs-boson phenomenology in five-dimensional warped supersymmetry

Constructing supersymmetric extensions of higher-dimensional models can have several motivations; it is, for instance, necessary in the context of string theories. Studying the supersymmetric version of the well-motivated model proposed by Randall and Sundrum, with the Higgs boson localized on the so-called TeV-brane, is not trivial since singularities appear in the Higgs couplings. Those are regularized by the contribution from the exchange of infinite towers of Kaluza-Klein (KK) scalar modes with Dirichlet-Dirichlet boundary conditions. Here we first derive the regularized four-dimensional (4D) effective Higgs couplings and induced sfermion mass matrices. A general method is provided for this regularization, based on the completeness relation. The sfermion masses must be obtained either from integrating out the mentioned KK towers or by treating their mixing effects, depending on the cases. We then use the obtained Higgs couplings and sfermion masses for some phenomenological applications. On one side, we show at the one-loop level how all quadratic divergences in the Higgs mass cancel out for any cutoff, due to 5D supersymmetry (SUSY) and to 5D anomaly cancellation; the analytical way followed here also allows a justification of the infinite KK summation required for the so-called KK regularization in 5D SUSY, which has motivated a rich literature. On the other side, we show that a certain pattern of SUSY breaking in the bulk would allow one to distinguish experimentally the minimal SUSY model \`a la Randall and Sundrum with bulk matter from the minimal 4D SUSY model, in the scenario where only superpartners were produced at the Large Hadron Collider. In this SUSY-breaking context, two of the discriminating tests developed make use of some different features arising in the squark or slepton mass spectrum. The other distinctive supersymmetric Randall-Sundrum feature is the possibly larger (even dominant) Higgs boson decay branching ratios into sleptons, compared to the 4D minimal supersymmetric standard model. In the same SUSY-breaking framework, techniques for pinning down the presence of soft SUSY-breaking terms on the TeV-brane are also suggested, based on the analysis of top squark pair production at the International Linear Collider.

Affleck-Dine baryogenesis, condensate fragmentation and gravitino dark matter in gauge-mediation with a large messenger mass

We study the conditions for successful Affleck-Dine baryogenesis and the origin of gravitino dark matter in GMSB models. AD baryogenesis in GMSB models is ruled out by neutron star stability unless Q-balls are unstable and decay before nucleosynthesis. Unstable Q-balls can form if the messenger mass scale is larger than the flat-direction field Φ when the condensate fragments. We provide an example based on AD baryogenesis along a d = 6 flat direction for the case where m3/2 ≈ 2GeV, as predicted by gravitino dark matter from Q-ball decay. Using a phenomenological GMSB potential which models the Φ dependence of the SUSY breaking terms, we numerically solve for the evolution of Φ and show that the messenger mass can be sufficiently close to the flat-direction field when the condensate fragments. We compute the corresponding reheating temperature and the baryonic charge of the condensate fragments and show that the charge is large enough to produce late-decaying Q-balls which can be the origin of gravitino dark matter.

Slepton Mass Matrices, µ→eγ Decay and EDM in SUSYS4Flavor Model

We discuss slepton mass matrices in the $S_4$ flavor model with SUSY SU(5) GUT. By considering the gravity mediation within the framework of supergravity theory, we estimate the SUSY breaking terms in the slepton mass matrices, which contribute to the $\mu \rightarrow e + \gamma$ decay. We obtain a lower bound for the ratio of $\mu\rightarrow e\gamma$ as $10^{-13}$ if $m_{\text{SUSY}}$ and $m_{1/2}$ are below 500GeV. The off diagonal terms of slepton mass matrices also contribute to EDM of leptons. The predicted electron EDM is around $10^{-29}-10^{-28}$cm. Our predictions are expected to be tested in the near future experiment.

Testing the gaugino AMSB model at the Tevatron via slepton pair production

Gaugino AMSB models — wherein scalar and trilinear soft SUSY breaking terms are suppressed at the GUT scale while gaugino masses adopt the AMSB form — yield a characteristic SUSY particle mass spectrum with light sleptons along with a nearly degenerate wino-like lightest neutralino and quasi-stable chargino. The left-sleptons and sneutrinos can be pair produced at sufficiently high rates to yield observable signals at the Fermilab Tevatron. We calculate the rate for isolated single and dilepton plus missing energy signals, along with the presence of one or two highly ionizing chargino tracks (HITs). We find that Tevatron experiments should be able to probe gravitino masses into the ∼55 TeV range for inoAMSB models (depending on detector-dependent HIT detection efficiency), which corresponds to a reach in gluino mass of over 1100 GeV.

Sparticle masses from transverse mass kinks at the LHC: the case of Yukawa-unified SUSY GUTs

We explore, in a concrete example, to which extent new particle mass determinations are practicable with LHC data. Our chosen example is that of Yukawa-unified SUSY GUTs, whose viability has been recently studied for two general patterns of soft SUSY-breaking terms. We note that both patterns of SUSY spectra do not admit long decay chains, which would make it possible to determine the masses of the SUSY particles involved using endpoints or mass relations. We thus take the so-called mT2-kink method as our key strategy, since it does not rely on the presence of long decay chains. We then discuss a procedure allowing to determine the masses of the gluino, of the lightest chargino as well as of the first two neutralinos and, for the scenario where a stop is lighter than the gluino, the mass of the light stop too. Our worked example of Yukawa-unified SUSY GUTs may offer a useful playground for dealing with other theories which predict similar patterns of SUSY spectra.

Tribimaximal mixing and Cabibbo angle inS4flavor model with supersymmetry

We present a flavor model of quarks and leptons with the non-Abelian discrete symmetry $S_4$ in the framework of the SU(5) SUSY GUT. Three generations of $\bar 5$-plets in SU(5) are assigned to ${\bf 3}$ of $S_4$ while the first and second generations of 10-plets in SU(5) are assigned to ${\bf 2}$ of $S_4$, and the third generation of 10-plet is assigned to ${\bf 1}$ of $S_4$. Right-handed neutrinos are also assigned to ${\bf 2}$ for the first and second generations and ${\bf 1}'$ for the third generation. We predict the Cabibbo angle as well as the tri-bimaximal mixing of neutrino flavors. We also predict the non-vanishing $U_{e3}$ of the neutrino flavor mixing due to higher dimensional mass operators. Our predicted CKM mixing angles and the CP violation are consistent with experimental values. We also study SUSY breaking terms in the slepton sector. Our model leads to smaller values of flavor changing neutral currents than the present experimental bounds.

Gaugino anomaly mediated SUSY breaking: phenomenology and prospects for the LHC

We examine the supersymmetry phenomenology of a novel scenario of supersymmetry (SUSY) breaking which we call Gaugino Anomaly Mediation, or inoAMSB. This is suggested by recent work on the phenomenology of flux compactified type IIB string theory. The essential features of this scenario are that the gaugino masses are of the anomaly-mediated SUSY breaking (AMSB) form, while scalar and trilinear soft SUSY breaking terms are highly suppressed. Renormalization group effects yield an allowable sparticle mass spectrum, while at the same time avoiding charged LSPs; the latter are common in models with negligible soft scalar masses, such as no-scale or gaugino mediation models. Since scalar and trilinear soft terms are highly suppressed, the SUSY induced flavor and CP-violating processes are also suppressed. The lightest SUSY particle is the neutral wino, while the heaviest is the gluino. In this model, there should be a strong multi-jet +etmiss signal from squark pair production at the LHC. We find a 100 fb^{-1} reach of LHC out to m_{3/2}\sim 118 TeV, corresponding to a gluino mass of \sim 2.6 TeV. A double mass edge from the opposite-sign/same flavor dilepton invariant mass distribution should be visible at LHC; this, along with the presence of short-- but visible-- highly ionizing tracks from quasi-stable charginos, should provide a smoking gun signature for inoAMSB.

Lepton flavour violation in the MSSM

We derive new constraints on the quantities δ XY ij , X, Y = L,R, which parametrise the flavour-off-diagonal terms of the charged slepton mass matrix in the MSSM. Considering mass and anomalous magnetic moment of the electron we obtain the bound $ \left| {\delta_{LL}^{13}\delta_{RR}^{{13}}} \right| \lesssim 0.{1} $ for tan β = 50, which involves the poorly constrained element δ RR 13. We improve the predictions for the decays τ → μγ, τ → eγ and μ → eγ by including two-loop corrections which are enhanced if tan β is large. The finite renormalisation of the PMNS matrix from soft SUSY-breaking terms is derived and applied to the charged-Higgs-lepton vertex. We find that the experimental bound on BR(τ → eγ) severely limits the size of the MSSM loop correction to the PMNS element U e3, which is important for the proper interpretation of a future U e3 measurement. Subsequently we confront our new values for δ LL ij with a GUT analysis. Further, we include the effects of dimension-5 Yukawa terms, which are needed to fix the Yukawa unification of the first two generations. If universal supersymmetry breaking occurs above the GUT scale, we find the flavour structure of the dimension-5 Yukawa couplings tightly constrained by μ → eγ.

Phenomenological Aspects of the Next-to-Minimal Supersymmetric Standard Model

The motivations for the NMSSM are reviewed, and possible unconventional signals for Higgs and sparticle production at the LHC are discussed. In the presence of a light pseudoscalar, the SM-like Higgs scalar can decay dominantly into a 4-tau final state. In the fully constrained NMSSM with mSUGRA-like soft SUSY breaking terms, the correct dark matter relic density is obtained for a singlino-like LSP which modifies considerably all sparticle decay chains.

Vacuum alignment in SUSY A 4 models

In this note we discuss the vacuum alignment in globally supersymmetric models with spontaneously broken flavour symmetries in the presence of generic soft supersymmetry (SUSY) breaking terms. We show that the inclusion of these soft SUSY breaking terms can give rise to non-vanishing vacuum expectation values (VEVs) for the auxiliary components of the flavon fields. These non-zero VEVs can have an important impact on the phenomenology of this class of models, since they can induce an additional flavour violating contribution to the sfermion soft mass matrix of right-left (RL) type. We carry out an explicit computation in a class of globally SUSY A 4 models predicting tribimaximal mixing in the lepton sector. The flavour symmetry breaking sector is described in terms of flavon and driving supermultiplets. We find non-vanishing VEVs for the auxiliary components of the flavon fields and for the scalar components of the driving fields which are of order m SUSY × 〈φ〉 and m SUSY, respectively. Thereby, m SUSY is the generic soft SUSY breaking scale which is expected to be around 1 TeV and 〈φ〉 is the VEV of scalar components of the flavon fields. Another effect of these VEVs can be the generation of a μ term.

Lepton flavor violation in supersymmetricB−Lextension of the standard model

Supersymmetric B-L extension of the Standard Model (SM) is one of the best candidate for physics beyond the SM that accounts for TeV scale seesaw mechanism and provides an attractive solution for the Higgs naturalness problem. We analyze the charged lepton flavor violation (LFV) in this class of models. We show that due to the smallness of Dirac neutrino Yukawa coupling, the decay rates of l_i -> l_j gamma and l_i -> 3 l_j, generated by the renormalization group evolution of soft SUSY breaking terms from GUT to seesaw scale, are quite suppressed. Therefore, this model is free from the stringent LFV constraints usually imposed on the supersymmetric seesaw model. We also demonstrate that the right-sneutrino is a long-lived particle and can be pair produced at the LHC through the B-L gauge boson. Then, they decay into same-sign dilepton, with a total cross section of order O(1) pb. This signal is one of the striking signatures of supersymmetric B-L extension of the SM.

Anatomy and phenomenology of FCNC and CPV effects in SUSY theories

We perform an extensive study of FCNC and CP Violation within Supersymmetric (SUSY) theories with particular emphasis put on processes governed by b → s transitions and of their correlations with processes governed by b → d transitions, s → d transitions, D 0 – D ¯ 0 oscillations, lepton flavour violating decays, electric dipole moments and ( g − 2 ) μ . We first perform a comprehensive model-independent analysis of Δ F = 2 observables and we emphasize the usefulness of the R b – γ plane in exhibiting transparently various tensions in the present UT analyses. Secondly, we consider a number of SUSY models: the general MSSM, a flavour-blind MSSM, the MSSM with Minimal Flavour Violation as well as SUSY flavour models based on Abelian and non-Abelian flavour symmetries that show representative flavour structures in the soft SUSY breaking terms. We show how the characteristic patterns of correlations among the considered flavour observables allow to distinguish between these different SUSY scenarios. Of particular importance are the correlations between the CP asymmetry S ψ ϕ and B s → μ + μ − , between the anomalies in S ϕ K S and S ψ ϕ , between S ϕ K S and d e , between S ψ ϕ and ( g − 2 ) μ and also those involving lepton flavour violating decays. In our analysis, the presence of right-handed currents and of the double Higgs penguin contributions to B s mixing plays a very important role. We propose a “DNA-Flavour Test” of NP models including Supersymmetry, the Littlest Higgs model with T-parity and the Randall–Sundrum model with custodial protection, with the aim of showing a tool to distinguish between these NP scenarios, once additional data on flavour-changing processes become available. As a byproduct, we present the SM prediction for BR ( B + → τ + ν ) = ( 0.80 ± 0.12 ) × 10 − 4 that follows solely from an analytical formula for this branching ratio in terms of Δ M s , d and S ψ K S asymmetry and which does not involve V u b and F B uncertainties.

Δ(54) flavor model for leptons and sleptons

We have studied $\Delta(54)\times Z_2$ flavor model for leptons and sleptons. The tri-bimaximal mixing can be reproduced for arbitrary neutrino masses if vacuum alignments of scalar fields are guaranteed. The deviation from the tri-bimaximal mixing of leptons is predicted. The predicted upper bound for $\sin\theta_{13}$ is 0.06. The magnitude of $\sin\theta_{23}$ could be deviated from the maximal mixing considerably, but $\sin\theta_{12}$ is hardly deviated from the tri-maximal mixing. We have also studied SUSY breaking terms in the slepton sector. Three families of left-handed and right-handed slepton masses are degenerate. Even although flavor symmetry breaking effects are taken into account, our model leads to smaller values of flavor changing neutral currents than the present experimental bounds.

On the full Boltzmann equations for leptogenesis

We consider the full Boltzmann equations for standard and soft leptogenesis, instead of the usual integrated Boltzmann equations which assume kineticequilibrium for all species. Decays and inverse decays may be inefficient for thermalising the heavy-(s)neutrino distribution function, leading to significant deviations from kinetic equilibrium. We analyse the impact of using the full kinetic equations in the case of a previously generated lepton asymmetry, and find that the washout of this initial asymmetry due to the interactions of the right-handed neutrino is larger than when calculated via the integrated equations. We also solve the full Boltzmann equations for soft leptogenesis, where the lepton asymmetry induced by the soft SUSY-breaking terms in sneutrino decays is a purely thermal effect, since at T = 0 the asymmetry in leptons cancels the one in sleptons. In this case, we obtain that in the weak washout regime (K ≲ 1) the final lepton asymmetry can change up to a factor four with respect toprevious estimates.

Electric dipole moments from spontaneous CP violation in SU(3)-flavoured SUSY

The SUSY flavour problem is deeply related to the origin of flavour and hence to the origin of the SM Yukawa couplings themselves. Since all CP-violation in the SM is restricted to the flavour sector, it is possible that the SUSY CP problem is related to the origin of flavour as well. In this work, we present three variations of an SU(3) flavour model with spontaneous CP violation. Such models explain the hierarchy in the fermion masses and mixings, and predict the structure of the flavoured soft SUSY breaking terms. In such a situation, both SUSY flavour and CP problems do not exist. We use electric dipole moments and lepton flavour violation processes to distinguish between these models, and place constraints on the SUSY parameter space.

Duality cascade of softly broken supersymmetric theories

We study the duality cascade of softly broken supersymmetric theories. We investigate the renormalization group (RG) flow of SUSY breaking terms as well as supersymmetric couplings. It is found that the magnitudes of SUSY breaking terms are suppressed in most regimes of the RG flow through the duality cascade. At one stage of cascading, the gaugino mass of the strongly coupled sector and scalar masses converge to certain values, which are determined by the gauge coupling and the gaugino mass of the weakly coupled sector. At the next stage, the strongly and weakly coupled sectors are interchanged with each other. We also show the possibility that cascading would be terminated by the gauge symmetry breaking, which is induced by the so-called B-term.

CP violation in [formula omitted] mixing in the SUSY SU(5) GUT with right-handed neutrinos

It is recently announced by the UTfit Collaboration that the CP phase of the Bs mixing amplitude, ϕBs, deviates more than 3σ from the Standard Model prediction. In this Letter we discuss how large correction to ϕBs is possible in the supersymmetric SU(5) ground unified model (SUSY SU(5) GUT) with right-handed neutrinos. Here, we assume the supergravity-like boundary condition for the SUSY-breaking terms. We found that the 95% probability region derived by the UTfit Collaboration is marginal in this model.