Sfermion Masses Research Articles

Direct and indirect detection of neutralino dark matter and collider signatures in anSO(10)model with two intermediate scales

We investigate the detectability of neutralino dark matter via direct and indirect searches as well as collider signatures of an $SO(10)$ model with two intermediate scales. We compare the direct dark matter detection cross section and the muon flux due to neutralino annihilation in the Sun that we obtain in this model with minimal supergravity predictions and with the sensitivity of current and future experiments. In both cases, we find that the detectability improves as the model deviates more from minimal supergravity. In order to study collider signatures, we choose two benchmark points that represent the main phenomenological features of the model: a lower value of $|\ensuremath{\mu}|$ and reduced third-generation sfermion masses due to extra Yukawa coupling contributions in the renormalization group equations and increased first- and second-generation slepton masses due to new gaugino loop contributions. We show that measurements at the LHC can distinguish this model from minimal supergravity in both cases, by counting events containing leptonically decaying ${Z}^{0}$ bosons, heavy neutral Higgs bosons, or like-sign lepton pairs. The methods we develop can be used more generally to characterize models of weak-scale supersymmetry.

Tree Level Mediation of Supersymmetry Breaking

We propose a new scheme in which supersymmetry breaking is communicated to the MSSM sfermions by GUT gauge interactions at the tree level. The (positive) contribution of MSSM fields to Str(ℳ2) is automatically compensated by a (negative) contribution from heavy fields. Sfermion masses are flavour universal, thus solving the supersymmetric flavour problem. In the simplest SO(10) embedding, the ratio of different sfermion masses is predicted and differs from mSugra and other schemes, thus making this framework testable at the LHC. Gaugino masses are generated at the loop level but enhanced by model dependent factors.

Direct gauge mediation of uplifted metastable supersymmetry breaking in supergravity

We propose a direct gauge mediation model based on an uplifted metastable supersymmetry (SUSY) breaking coupled to supergravity. A constant superpotential plays an essential role to fix the moduli as well as breaking SUSY and $R$ symmetry and the cancellation of the cosmological constant. Gaugino masses are generated at leading order of SUSY breaking scale, and comparable to the sfermion masses as in the ordinary gauge mediation. The Landau pole problem for QCD coupling can be easily solved since more than half of messengers become superheavy, which are heavier than the grand unified theory (GUT) scale.

Renormalization in general gauge mediation

We revisit General Gauge Mediation (GGM) in light of the supersymmetric (linear) sigma model by utilizing the current superfield. The current superfield in the GGM is identified with supersymmetric extension of the vector symmetry current of the sigma model while spontaneous breakdown of supersymmetry in the GGM corresponds to soft breakdown of the axial vector symmetry of the sigma model. We first derive the current superfield from the supersymmetric linear sigma model and then compute 2-point functions of the current superfield using the (anti-)commutation relations of the messenger component fields. After the global symmetry are weakly gauged, the 2-point functions of the current superfield are identified with a part of the 2-point functions of the associated vector superfield. We renormalize them by dimensional regularization and show that physical gaugino and sfermion masses of the MSSM are expressed in terms of the wavefunction renormalization constants of the component fields of the vector superfield.

SUSY_FLAVOR: A computational tool for FCNC and CP-violating processes in the MSSM

We present SUSY_FLAVOR – a Fortran 77 program that calculates important leptonic and semi-leptonic low-energy observables in the general R-parity conserving MSSM. For a set of input MSSM parameters, the code gives predictions for the K ¯ 0 K 0 , D ¯ D , B ¯ d B d and B ¯ s B s mixing parameters; B → X s γ , B s , d → l + l − , K L 0 → π 0 ν ¯ ν and K + → π + ν ¯ ν decay branching ratios; and the electric dipole moments of the leptons and the neutron. All these quantities are calculated at one-loop level (with some higher-order QCD corrections included) in the exact sfermion mass eigenbasis, without resorting to mass insertion approximations. The program can be obtained from http://www.fuw.edu.pl/susy_flavor. Program summary Program title: SUSY_FLAVOR Catalogue identifier: AEGV_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEGV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 14 603 No. of bytes in distributed program, including test data, etc.: 82 126 Distribution format: tar.gz Programming language: Fortran 77 Computer: PCs and workstations Operating system: Any, tested on Linux Classification: 11.6 Nature of problem: Predicting CP-violating observables, meson mixing parameters and branching ratios for a set of rare processes in the general R-parity conserving MSSM. Solution method: We use standard quantum theoretical methods to calculate Wilson coefficients in MSSM and at one loop including QCD corrections at higher orders when this is necessary and possible. The input parameters can be read from an external file in SLHA format. Restrictions: The results apply only to the case of MSSM with R-parity conservation. Running time: For single parameter set approximately 1 s in double precision on a PowerBook Mac G4.

General gauge mediation in five dimensions

We use the ``general gauge mediation'' (GGM) formalism to describe a five-dimensional setup with an ${S}^{1}/{\mathbb{Z}}_{2}$ orbifold. We first consider a model independent supersymmetry breaking hidden sector on one boundary and generic chiral matter on another. Using the definition of GGM, the effects of the hidden sector are contained in a set of global symmetry current correlator functions and is mediated through the bulk. We find the gaugino, sfermion and hyperscalar mass formulas for minimal and generalized messengers in different regimes of a large, small and intermediate extra dimension. Then we use the five-dimensional GGM formalism to construct a model in which an $SU(5)$ Intriligator, Seiberg and Shih (ISS) model is located on the hidden boundary. We weakly gauge a global symmetry of the ISS model and associate it with the bulk vector superfield. Compared to four-dimensional GGM, there is a natural way to adjust the gaugino versus sfermion mass ratio by a factor $(M\ensuremath{\ell}{)}^{2}$, where $M$ is a characteristic mass scale of the supersymmetry breaking sector and $\ensuremath{\ell}$ is the length of the extra dimension.

Semidirect gauge mediation in conformal windows of vectorlike gauge theories

Direct gauge mediation models using the Intriligator-Seiberg-Shih metastable vacua suffer from the Landau pole problem of the standard-model gauge couplings and the existence of $R$-symmetry forbidding gaugino masses. These problems may be solved by using the recently proposed supersymmetry (SUSY)-breaking models in a conformal window of the vectorlike $SU({N}_{C})$ gauge theory with gauge singlets. In this paper we propose a model of gauge mediation based on the SUSY-breaking model in the conformal window, and study the dynamics for SUSY breaking. In this model, there are massive vectorlike bifundamental fields charged under both $SU({N}_{C})$ and the standard-model gauge group, and our model can be regarded as a semidirect gauge mediation model. The color number ${N}_{C}$ can be small to avoid the Landau pole problem, and $R$ symmetry is also broken under a reasonable assumption on the strong dynamics of the model. The model possesses only one free parameter, and the gaugino and sfermion masses are naturally of the same order.

Suppression of lepton flavour violation from quantum corrections above M GUT

We study the predictions for sfermion masses and Lepton Flavour Violation (LFV) for the WMAP preferred parameter space in $b-\tau$ Yukawa-unified models with massive neutrinos. A soft term structure as predicted by an Abelian flavour symmetry combined with SU(5) RGEs for scales above $M_{GUT}$, results to an efficient suppression of the off-diagonal terms in the scalar soft matrices, particularly for $m_0< 100$ GeV. Using the WMAP bounds, this implies $35\le\tan\beta \le 45$, $350\,\mathrm{GeV}\le m_{1/2}\le 1\,\mathrm{TeV}$, with the higher $\tan\beta$ values being favored. Within this framework, SU(5) unification becomes compatible with the current experimental bounds, in contrast to the conventional case where the soft terms are postulated at the GUT scale.

General messenger gauge mediation

We discuss theories of gauge mediation in which the hidden sector consists of two subsectors which are weakly coupled to each other. One sector is made up of messengers and the other breaks supersymmetry. Each sector by itself may be strongly coupled. We provide a unifying framework for such theories and discuss their predictions in different settings. We show how this framework incorporates all known models of messengers. In the case of weakly-coupled messengers interacting with spurions through the superpotential, we prove that the sfermion mass-squared is positive, and furthermore, that there is a lower bound on the ratio of the sfermion mass to the gaugino mass.

General aspects of tree level gauge mediation

Tree level gauge mediation (TGM) may be considered as the simplest way to communicate supersymmetry breaking: through the tree level renormalizable exchange of heavy gauge messengers. We study its general structure, in particular the general form of tree level sfermion masses and of one loop, but enhanced, gaugino masses. This allows us to set up general guidelines for model building and to identify the hypotheses underlying the phenomenological predictions. In the context of models based on the "minimal" gauge group SO(10), we show that only two "pure" embeddings of the MSSM fields are possible using $d< 120$ representations, each of them leading to specific predictions for the ratios of family universal sfermion masses at the GUT scale, $m^2_{\bar{5}} = 2 m^2_{10}$ or $m^2_{\bar{5}} = (3/4) m^2_{10}$ (in SU(5) notation). These ratios are determined by group factors and are peculiar enough to make this scheme testable at the LHC. We also discuss three possible approaches to the $\mu$-problem, one of them distinctive of TGM.

Patterns of soft masses from general semi-direct gauge mediation

We give a general formulation of semi-direct gauge mediation of supersymmetry breaking where the messengers interact with the hidden sector only through a weakly gauged group. Using this general formulation, we provide an explicit proof that the MSSM gaugino masses are vanishing to leading order in the gauge couplings. On the other hand, the MSSM sfermion masses have, generically, a non-vanishing leading contribution. We discuss how such a mechanism can successfully be combined with other mediation schemes which give tachyonic sfermions, such as sequestered anomaly mediation and some direct gauge mediation models.

Direct mediation and metastable supersymmetry breaking for SO(10)

We examine a metastable $\mathcal{N}=1$ Macroscopic SO(N) SQCD model of Intriligator, Seiberg and Shih (ISS). We introduce various baryon and meson deformations, including multitrace operators and explore embedding an SO(10) parent of the standard model into two weakly gauged flavour sectors. Direct fundamental messengers and the symmetric pseudo-modulus messenger mediate SUSY breaking to the MSSM. Gaugino and sfermion masses are computed and compared for each deformation type. We also explore reducing the rank of the magnetic quark matrix of the ISS model and find an additional fundamental messenger.

Flavour geometry and effective Yukawa couplings in the MSSM

We present a new geometric approach to the flavour decomposition of an arbitrary soft supersymmetry-breaking sector in the MSSM. Our approach is based on the geometry that results from the quark and lepton Yukawa couplings, and enables us to derive the necessary and sufficient conditions for a linearly-independent basis of matrices related to the completeness of the internal [SU(3)⊗U(1)]5 flavour space. In a second step, we calculate the effective Yukawa couplings that are enhanced at large values of tan β for general soft supersymmetry-breaking mass parameters. We highlight the contributions due to non-universal terms in the flavour decompositions of the sfermion mass matrices. We present numerical examples illustrating how such terms are induced by renormalization-group evolution starting from universal input boundary conditions, and demonstrate their importance for the flavour-violating effective Yukawa couplings of quarks.

Tree level metastability and gauge mediation in baryon deformed SQCD

We investigate supersymmetric QCD with gauge group SU(2) and a baryon deformation to the superpotential. The existence of an uplifted vacuum at the origin with tree level metastability is demonstrated. When this model is implemented in a direct gauge mediation scenario we therefore find gaugino masses which are comparable to sfermion masses and parameterised by an effective number of messengers 1/8. All deformations are well motivated by appealing to the electric theory and an R-symmetry. This R-symmetry is explicitly broken by the same term responsible for supersymmetry breaking. Moreover, the model does not suffer from the Landau pole problem and we find that it can be described in terms of just two scales: the weak scale and a high scale like the Planck or GUT scale. The model can be tested by searching for new particles at the TeV scale charged under the visible sector gauge group.

Tree level gauge mediation

We propose a new scheme in which supersymmetry breaking is communicated to the MSSM sfermions by GUT gauge interactions at the tree level. The (positive) contribution of MSSM fields to Str(2) is automatically compensated by a (negative) contribution from heavy fields. Sfermion masses are flavour universal, thus solving the supersymmetric flavour problem. In the simplest SO(10) embedding, the ratio of different sfermion masses is predicted and differs from mSugra and other schemes, thus making this framework testable at the LHC. Gaugino masses are generated at the loop level but enhanced by model dependent factors.

Gaugino versus sfermion masses in gauge mediation

A well-known signature of supersymmetry breaking scenarios with ordinary gauge mediation is a universal formula governing gaugino and sfermion masses such that their ratio is of order one. On the other hand, recently studied models with direct gauge mediation predict anomalously small ratios of gaugino to scalar masses. It was argued that the smallness of gaugino masses is a consequence of being in the lowest energy state of the SUSY-breaking low energy effective theory. To increase gaugino masses one either has to move to higher metastable vacuum or alternatively remain in the original SUSY-breaking vacuum but extend the theory by introducing a lower-lying vacuum elsewhere. We follow the latter strategy and show that the ratio of gaugino to sfermion masses can be continuously varied between zero and of order one by bringing in a lower vacuum from infinity. We argue that the stability of the vacuum is directly linked to the ratio between the gaugino masses and the underlying SUSY-breaking scale, i.e. the gravitino mass.

Automatized full one-loop renormalization of the MSSM. II. The chargino-neutralino sector, the sfermion sector, and some applications

An on-shell renormalization program for the chargino/neutralino and the sfermion sectors within the minimal supersymmetric standard model as implemented in a fully automated code, sloops, for the calculation of one-loop processes at the colliders and in astrophysics, is presented. This is a sequel to our previous study where an on-shell renormalization of the Higgs (and the gauge/fermion) sector is performed. The issue of mixing is treated in a unified and coherent manner in all these sectors, in particular, we give some new insight into the renormalization of the mixing angle in the sfermion sector. Like with the issue of $\mathrm{tan}\ensuremath{\beta}$ in the Higgs sector, we discuss different schemes for the mixing in the sfermion sector. We also perform numerical comparisons between our code sloops and different results found in the literature. In particular, we consider loop corrections to the neutralino and sfermion masses, chargino pair production and stau pair production in ${e}^{+}{e}^{\ensuremath{-}}$ colliders as well as a few decays of the heavier chargino. For all these observables, we analyze the $\mathrm{tan}\ensuremath{\beta}$ scheme dependence using different definitions of this parameter and comment on the impact of using different renormalization of the mixing parameter in the sfermion sector.

LHC signature of supersymmetric models with non-universal sfermion masses

We study the LHC signature of the minimal supersymmetric standard model with non-universal sfermion masses. In the model, soft masses of gauginos and the 3rd generation of 10 of SU(5) are around the weak scale, while other sfermion soft mass is universal and around a few TeV. Such sfermion mass spectrum is motivated not only from flavor, CP and naturalness constraints but also from E_6 grand unified model with non-Abelian horizontal (flavor) symmetry. The characteristic signature of the model at the LHC is the dominance of the events with 4 b partons in the final state together with high rate of mildly boosted top quark arising from gluino decay. The prominent high p_T jet also arises from squark decay. We show it is possible to find the characteristic signature in the early stage of the LHC. The discrimination of our scenario from some CMSSM model points with similar signature may be possible with large integrated luminosity. The result of sparticle mass measurement using exclusive channel with the help of hemisphere analysis, and inclusive measurement of gluino and squark masses using M_{T2} and M_{T2}^{min} in some representative model points are presented.

CEDM Constraints on Modified Sfermion Universality and Spontaneous CP Violation

We discuss the supersymmetric CP problem that arises when the sfermion soft mass universality is modified. We place the 3rd generation SU(5) ten-plet sfermion masses in the weak scale in view of the naturalness. The other sfermion masses are assumed to be universal and a TeV scale in order to weaken the flavor changing neutral current processes and electric dipole moment (EDM) constraints. However this modification generically induces too large up quark chromo-EDM (CEDM) via the weak scale stop loop. In order to suppress this CEDM, we propose certain type of flavor structure where the parameters of the up-(s)quark sector are real whereas those of the down-(s)quark and the charged (s)lepton sectors are complex at the GUT scale. It is shown that, in this set up, up quark CEDM can be suppressed within the range where the current and future experiments have their sensitivity. We briefly illustrate the simple realization of these particular forms of the modified sfermion universality with real up-(s)quark sector by spontaneous CP violation in E$_6$ SUSY GUT with SU(2) flavor symmetry.

Gauge extensions of supersymmetric models and hidden valleys

Supersymmetric models with extended group structure beyond the standard model are revisited in the framework of general gauge mediation. Sum rules for sfermion masses are shown to depend genuinely on the group structure, which can serve as important probes for specific models. The left-right model and models with extra U(1) are worked out for illustrations. If the couplings of extra gauge groups are small, supersymmetric hidden valleys of the scale 10-100 GeV can be naturally constructed in companion of a TeV-scale supersymmetric visible sector.