Ken-Iti Izawa

Dynamical Supersymmetry Breaking in Vector-Like Gauge Theories

We provide vector-like gauge theories which break supersymmetry dynamically. ⋆ JSPS Research Fellow. There is a piece of folklore which holds that vector-like gauge theories cannot break supersymmetry dynamically. In this letter, we point out remarkable exceptions to this piece of folklore. Let us consider a supersymmetric SU(2) gauge theory with four doublet chiral superfields Qi. We also introduce six singlet chiral superfields Z ij = −Z. Here i and j denote the flavor indices (i, j = 1, · · · , 4). The tree-level superpotential of our model is given by † Wtree = λ kl ijZ QkQl, (1) where λ ij denote generic coupling constants with λ kl ij = −λ kl ji = −λ lk ij . The pecuriarity of this superpotential resides in that it raises all the D-flat directions in the doublets Qi, which is a necessary condition for supersymmetry to break down. [1] Of course, supersymmetry remains unbroken perturbatively in this model. The exact effective superpotential of the model, which takes into account the full nonperturbative effects, may be written in terms of gauge-invariant low-energy degrees of freedom [2] Vij = −Vji ∼ QiQj (2) as follows: Weff = X(PfVij − Λ ) + λ ijZ Vkl, (3) where X is an additional chiral superfield, PfVij denotes the Pfaffian of the antisymmetric matrix Vij, and Λ is a dynamical scale of the SU(2) gauge interaction. [2,3] † This tree-level superpotential is natural since it possesses two global symmetries. One is an axial U(1) symmetry associated with a Qi phase transformation and the other is an anomaly-free R symmetry. 2 This is none other than a superpotential of the O’Raifeartaigh type. [4] Namely, this effective superpotential yields conditions for supersymmetric vacua PfVij = Λ , λ ijVkl = 0, (4) which cannot be satisfied simultaneously as far as Λ 6= 0. Therefore we conclude that supersymmetry is dynamically broken in our model. We note that this conclusion is not in contradiction with the index argument. [5] The doublets Qi cannot be decoupled by means of mass terms m QiQj since the apparent masses may be absorbed in the shifts of the singlets Z . It is straightforward to generalize the above model to an Sp(N) gauge theory [6] with 2(N +1) chiral superfields in the 2N representation. Here we adopt a notation Sp(1) = SU(2). These vector-like models might serve as a supersymmetry-breaking mechanism in the hidden [7] or visible sector.

Direct-transmission models of dynamical supersymmetry breaking

We systematically construct gauge-mediated supersymmetry- (SUSY-) breaking models with direct transmission of SUSY-breaking effects to the standard-model sector. We obtain a natural model with the gravitino mass m{sub 3/2} smaller than 1 keV as required from the standard cosmology. If all Yukawa coupling constants are of order one, the SUSY-breaking scale m{sub SUSY} transmitted into the standard-model sector is given by m{sub SUSY}{approx_equal}0.1({alpha}{sub i}/4{pi}){Lambda} where {Lambda} is the original dynamical SUSY-breaking scale. Imposing m{sub SUSY}{approx_equal}(10{sup 2}{endash}10{sup 3}) GeV, we get {Lambda}{approx_equal}(10{sup 5}{endash}10{sup 6}) GeV, which yields the gravitino mass m{sub 3/2}{approx_equal}(10{sup {minus}2}{endash}1) keV. {copyright} {ital 1997} {ital The American Physical Society}

Natural new inflation in broken supergravity

Abstract We consider a natural new inflationary model in broken supergravity based on an R symmetry. The model predicts a concrete relation between the amplitude of primordial density fluctuations and the scale of supersymmetry breaking. The observed value of the density fluctuations is obtained for the gravitino mass of order the weak scale along with a power-law spectral index considerably less than one, which may be tested in future observations.

Conformally sequestered supersymmetry breaking in vectorlike gauge theories

We provide, in a framework of vectorlike gauge theories, concrete models for conformal sequestering of dynamical supersymmetry (SUSY) breaking in the hidden sector. If the sequestering is sufficiently strong, anomaly mediation of the SUSY breaking may give dominant contributions to the mass spectrum of SUSY standard model particles, leading to negative slepton masses squared. Thus, we also consider a model with gravitational gauge mediation to circumvent the tachyonic slepton problem in pure anomaly-mediation models.

Dynamical tuning of the initial condition for new inflation in supergravity

Abstract We point out that for a class of ‘new inflation’ models in supergravity the required initial value of the inflaton field is dynamically set if there is another inflation (‘pre-inflation’) before the ‘new inflation’. We study the dynamics of both inflatons by taking a hybrid inflation model for the ‘pre-inflation’ as an example. We find out that our ‘new inflation’ model provides reheating temperatures T R ⋍ 10 MeV –10 4 MeV low enough to avoid the gravitino problem even in gauge-mediated supersymmetry-breaking models. We also construct a model where the scale for the ‘new inflation’ is generated by nonperturbative dynamics of a supersymmetric gauge theory.

Dynamical models for light Higgs doublets in supersymmetric grand unified theories

We consider a supersymmetric hypercolor gauge theory with six flavors of (hyper)quarks interacting strongly at the grand unification scale. Dynamical breaking of the grand unified SU(5

More on conformally sequestered supersymmetric breaking

{)}_{\mathrm{}\mathrm{GUT}}

Strongly Coupled Gauge Mediation

produces a massless pair of composite color-triplet states. Use of the missing partner mechanism yields eventually a pair of massless Higgs doublets, giving large masses to the color-triplet partners. We prove that this pair of massless Higgs doublets survives quantum corrections and remains in the low-energy spectrum as long as the supersymmetry is unbroken. Hence this could solve the most serious problem\char22{}doublet-triplet splitting in the grand unified theories. We also show that the dangerous dimension-five operators for nucleon decays are suppressed simultaneously, which makes our model still more attractive. \textcopyright{} 1996 The American Physical Society.

Dynamical supersymmetry breaking without messenger gauge interactions

We extend our models for conformal sequestering of dynamical supersymmetry breaking with decoupling vectorlike matter in several different ways. These extensions enable us to simplify concrete model building, in particular, rendering large gauge group and ad hoc global symmetry for sequestering unnecessary. Conformal sequestering appears highly natural in such circumstances.

On Nonlinear Gauge Theory from a Deformation Theory Perspective

A model of gauge mediation with m 3/2 ≃ O(1)eV is considered to motivate 100 TeV colliders. Massive mediators with standard-model and supersymmetry-breaking gauge quantum numbers let low-scale dynamics induce sizable soft masses of the standard-model superpartners. We circumvent potential phenomenological difficulties that such low-scale models tend to cause.