Supersymmetric Effective Lagrangian Research Articles

Minimal model of gravitino dark matter

Motivated by the absence of signals of new physics in both searches for new particles at LHC and for a Weakly Interacting Massive Particle (WIMP) dark matter candidate, we consider a scenario where supersymmetry is broken at a scale above the reheating temperature. The low energy particle content consists then only in Standard Model states and a gravitino. We investigate the possibility that the latter provides the main component of dark matter through a freeze in mechanism from annihilation of thermalized Standard Model particles. We focus on the case where its production through scattering in the thermal plasma is well approximated by the non-linear supersymmetric effective Lagrangian of the associated goldstino and identify the parameter space allowed by the cosmological constraints, allowing the possibility of large reheating temperature compatible with leptogenesis scenarios, alleviating the so called "gravitino problem".

Supersymmetric Higgs searches: Beyond the MSSM

The recent results from the ATLAS and CMS Collaborations show that the allowed range for a standard model Higgs boson is now restricted to a very thin region, if one excludes a very heavy Higgs. Although those limits are presented exclusively in the framework of the standard model, the searches themselves remain sensitive to other Higgs models. We recast the limits within a generic supersymmetric framework that goes beyond the usual minimal extension. Such a generic model can be parametrized through a supersymmetric effective Lagrangian with higher-order operators appearing in the K\"ahler potential and the superpotential, an approach whose first motivation is to alleviate the fine-tuning problem in supersymmetry with the most dramatic consequence being a substantial increase in the mass of the lightest Higgs boson as compared to the minimal supersymmetic model. We investigate in this paper the constraints set by the LHC on such models. We also investigate how the present picture will change when gathering more luminosity. Issues of how to combine and exploit data from the LHC dedicated to searches for the standard model Higgs to such supersymmetry inspired scenarios are discussed. We also discuss the impact of invisible decays of the Higgs in such scenarios.

Manifestly supersymmetric effective Lagrangians on BPS solitons

A systematic method to obtain the effective Lagrangian on the Bogomol'nyi-Prasad-Sommerfield background in supersymmetric gauge theories is worked out, taking domain walls and vortices as concrete examples. The Lagrangian in terms of the superfields with four preserved supercharges is expanded in powers of the slow-movement parameter $\ensuremath{\lambda}$. The expansion gives the superfield form of the Bogomol'nyi-Prasad-Sommerfield equations at $\mathcal{O}({\ensuremath{\lambda}}^{0})$, and all the fluctuation fields at $\mathcal{O}({\ensuremath{\lambda}}^{1})$. The density of the K\"ahler potential for the effective Lagrangian follows as an automatic consequence of the $\ensuremath{\lambda}$ expansion making (four preserved) supercharges manifest.

NONLINEAR SUPERSYMMETRIC EFFECTIVE LAGRANGIAN AND GOLDSTINO INTERACTIONS AT HIGH ENERGIES

We show that the nonlinear supersymmetric effective Lagrangian can be used for model-independent parametrization of the light gravitino scattering amplitude at energies up to and above the soft supersymmetry-breaking masses. This provides the most convenient framework for systematic studies of goldstino phenomenology both at low energies and in high energy colliders.

Toy model for breaking super gauge theories at the effective Lagrangian level

We propose a toy model to illustrate how the effective Lagrangian for super QCD might go over to the one for ordinary QCD by a mechanism whereby the gluinos and squarks in the fundamental theory decouple below a given supersymmetry breaking scale $m$. The implementation of this approach involves a suitable choice of possible supersymmetry breaking terms. An amusing feature of the model is the emergence of the ordinary QCD degrees of freedom which were hidden in the auxiliary fields of the supersymmetric effective Lagrangian.

New symmetries of supersymmetric effective Lagrangians.

We consider the structure of effective lagrangians describing the low-energy dynamics of supersymmetric theories in which a global symmetry $G$ is spontaneously broken to a subgroup $H$ while supersymmetry is unbroken. In accordance with the supersymmetric Goldstone theorem, these lagrangians contain Nambu--Goldstone superfields associated with a coset space $G^c / \hat{H}$, where $G^c$ is the complexification of $G$ and $\hat{H}$ is the largest subgroup of $G^c$ that leaves the order parameter invariant. The lagrangian may also contain additional light matter fields. To analyze the effective lagrangian for the matter fields, we first consider the case where the effective lagrangian is obtained by integrating out heavy modes at weak coupling (but including non-perturbative effects such as instantons). We show that the superpotential of the matter fields is $\hat{H}$ invariant, which can give rise to non-trivial relations among independent $H$-invariants in the superpotential. We also show that the Kahler potential of the matter fields can be restricted by a remnant of $\hat{H}$ symmetry. These results are non-perturbative and have a simple group-theoretic interpretation. When we relax the weak-coupling constraint, there appear to be additional possibilities for the action of $\hat{H}$ on the matter fields, hinting that the constraints imposed by $\hat{H}$ may be even richer in strongly coupled theories.

Moduli dependence of string loop corrections to gauge coupling constants

We consider one-loop corrections 4 Δ a to inverse gauge couplings g a −2 in supersymmetric vacua of the heterotic string. The form of these corrections plays an important role in scenarios for dynamical supersymmetry breaking in string theory. Specifically, we calculate the exact functional dependence of Δ a ( U) on any untwisted modulus field U of an orbifold vacuum; it has the universal form Δ a(U, U)=A a· log(|η(U)| 4· lm U)+ const. , where A a are easily computable rational constants. The dependence is nontrivial ( A a ≠0) only if some sectors of the orbifold Hilbert space have precisely N=2 space-time supersymmetry. The expression for Δ a has an expected invariance under modular transformations of U, since these are symmetries of the orbifold vacuum state. However, Δ a is not the real part of a holomorphic function, in seeming contradiction with the existence of a supersymmetric effective lagrangian. The apparent paradox is an infrared problem, and can occur not just in string theory but in renormalizable supersymmetric field theories as well. We show how the paradox is resolved in the field theory case and argue that the same resolution applies also to the string theory case.

Supersymmetric effective Lagrangians for matter-goldstone multiplet interactions

The supersymmetric effective lagrangian describing the spontaneous breakdown of the group G to an invariant subgroup H is constructed, which includes the invariant coupling of the nonlinearly transforming Goldstone superfields to linearly transforming matter superfields.

Anomaly constraints on supersymmetric effective lagrangians

In this paper we set constraints on the possible effective-lagrangian representations of supersymmetric gauge theories with spontaneously broken chiral flavor symmetries, by finding the conditions under which a Wess-Zumino term to represent the anomalous interactions can be constructed. We find that effective lagrangians for such theories are possible only for nonlinear sigma models defined on noncompact manifolds, and demonstrate the realization of this result in supersymmetric QCD. We also consider the Wess-Zumino term in the nonlinear realization of broken supersymmetry.

Internal symmetry currents and supersymmetric effective lagrangians

A supersymmetric and non-linearly realized internally symmetric action is constructed from the super Kähler potential of Goldstone scalar superfields. Noether's theorem in superspace is derived and the associated superfield of currents defined. The currents are used to derive a super Dashen formula relating the (quasi) Goldstone masses and decay constants to the symmetry breaking part of the theory and to supersymmetrically gauge the invariant subgroup as well as the full group.